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The influence of orientation on the creep behaviors of a 3rd generation single crystal superalloy was studied at 850 °C. It is found that the creep properties are highly anisotropic for [001], [011] and [111] specimens. The [111] samples show the longest creep life. The [011] specimens display the shortest creep life of less than 1 h and the longest elongation. And [001] specimens exhibit the intermediate creep life. Electron backscattered diffraction (EBSD) analyses and transmission electron microscopy (TEM) observations show that the creep anisotropy is mainly related to the slip systems that activated, especially the {111} slip systems. Single slip of {111} system results in a high creep strain and poor property, which controls the primary creep of [001] and entire creep stage of [011] specimens. While interaction of primary and secondary {111} systems has an effect on work hardening, which occurs during steady and tertiary creep of [111] orientation and hence results in the best creep property of [111] specimens. By comparing with SRR99 and CMSX-4 alloys, higher Re content in DD33 alloy may facilitate the formation of continuous stacking faults in [011] specimens and activation of multiple {111} slip systems in [111] specimens, which will affect the creep property and anisotropy.

This work focuses on the plastic deformation behavior and microstructure evolution in high temperature sheet bulk forming of 2219 aluminum alloy. Uniaxial compression tests were carried out along the normal direction (ND), transverse direction (TD) and rolling direction (RD) of an annealed rolled sheet which has brick-like grains but weak texture. Electron backscattered diffraction (EBSD) was employed to observe the microstructure after compression deformation. Experimental results show strong anisotropy in plastic flow in spite of non-prominent anisotropy in strength. Meanwhile, grain refinement mechanisms transform from geometric dynamic recrystallization (GDRX) in ND compression to discontinuous dynamic recrystallization (DDRX) with enhanced particle stimulated nucleation (PSN) effect in TD and RD compressions. Grain morphology has little effect on the plastic anisotropy. However, the heterogeneous deformation associated with the distortion of brick-like grains in compression accounts for the diverse microstructural developments to a large extent.

Carbide-free bainitic steel is one of the most widely manufactured and applied materials. In this paper, its behavior in uniaxial tensile deformation is studied in quasi-in-situ conditions. The microstructure evolution of bainitic ferrite and retained austenite during tensile deformation was investigated by scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and X-ray diffraction. Results indicate that the sequence of the multiscale retained austenite transformed to martensite from easy to difficulty is blocky (micron level), flake (sub-nano level) and film-like (nano-size). The blocky retained austenite undergoes a martensitic transformation at the elastic stage, where a “bainitic ferrite-soft austenite-hard martensite” structure is formed. With increasing strain, the flake retained austenite between the bainitic ferrite plates plays a positive role, which is accompanied by continuous strain-induced martensitic transformation. Finally, a refined microstructure consisting of “bainitic ferrite-soft austenite-hard martensite-soft austenite” is formed. In the final non-uniform strain fracture process, the nano film-like retained austenite finally begins to transform to martensite owing to its extreme mechanical stability. In addition, the film-like retained austenite itself becomes part of the combination structure of “bainitic ferrite and austenite”.

In the present work, aluminium alloys were subjected to two different severe plastic deformation (SPD) routes namely, cryorolling (CYR) and constrained groove pressing (CGP), to investigate their effect on microstructure and mechanical properties. Solutionized AA 5083 alloy and AA 6061 alloy sheets were cryorolled to a final thickness of 1 mm with a total logarithmic strain of 1.87. Samples of these alloys with 3 mm thickness were subjected to CGP with an equivalent plastic strain of 1.16. The CGP samples have been subsequently cold rolled (CR) to reduce the thickness to 1 mm (67% reduction). The microstructure of the deformed samples was characterized by electron backscatter diffraction (EBSD) coupled with kernel average misorientation (KAM) and X-ray diffraction (XRD). The techniques were employed to investigate the degree of grain refinement and local misorientation due to deformation. It has been found that the yield strength (YS) of 6061 alloy after CGP + CR is 19% higher than that of CYR sample while, in contrast, the YS of CGP + CR 5083 alloy is 18% less than that of CYR condition. A dislocation density-based model has been used to estimate the sub-structural changes during processing. The theoretical dislocation density estimated using the model agreed well with the experimental values of both the alloys with a difference of about 2.5% in the case of 5083 and 6.5% in the case of 6061. It is inferred from the analysis that the dislocation bow out is the predominant mechanism in both the materials.

Hot deformation characteristics of 410 stainless and K100 tool steels were compared through hot compression tests in temperature range of 800–1200 °C and strain rates of 0.001-1 s-1. Carbon content is the major difference between the studied steels. Its higher content in K100 leads to a considerable amount of carbide particles even after reheating and through hot working; whereas, they are absent in 410 due to its lower C content. The flow curves of K100 showed fast work hardening at low strain levels and distinct peaks implying the occurrence of DRX. However, the flow curves of 410 exhibites more gradual work hardening and the peaks appeared at larger strains. It was concluded that dynamic recrystallization (DRX) in K100 precedes that in 410. However, the Avrami model suggested that DRX in 410 is faster than that in K100. Constitutive analysis showed that K100 has higher apparent activation energy at the peak but lower at strain of 0.5. The primary and dynamically precipitated carbides were found responsible for the higher deformation resistance of K100 at the peak. Observations by EBSD confirmed that discontinuous and continuous DRX are the dominant recrystallization mechanisms in 410 and K100, respectively. The higher internal deformation energy due to the existence of fine carbide particles is the major reason for the start of DRX at lower strains in K100. However, despite the sluggish nature of continuous DRX in K100, discontinuous DRX in 410 proceeds faster.

In the present work, strain localization at the surface of a heavily textured material is modeled, where the subsurface microstructure was statistically reconstructed via a proposed methodology that directly uses the information given by the surface characterization. The elasto-viscoplastic simulations based within a fast Fourier transformation formulation (EVP-FFT) were compared with digital image correlation quantification of strain coupled with electron backscatter diffraction characterization of the microstructure to produce strain maps of the surfaces, and the in-plane maximum shear strain was evaluated. When modeling specimens from rolled plate of AA7050 material, both with and without a 3D subsurface reconstruction, a reasonable improvement was observed when a statistically reconstructed subsurface morphology was included in the simulations (regardless of grain morphology or orientation distribution) since it allowed the surface grains to redistribute and accommodate deformation along the third dimension. Additionally, when performing a case study on fabricated specimens that exhibited a through thickness grain structure, in order to minimize the subsurface uncertainty, the model's ability to capture the strain localization improved, thereby confirming the importance of capturing the subsurface microstructure on the surface response. These results therefore quantify the effect of the subsurface grain structure on the surface strain fields and thereby present a path forward for performing crystal plasticity simulations by presenting a subsurface reconstruction methodology based on surface characterizations.

Deformation mechanisms during uniaxial compressive loading of two extruded binary Mg − 3Nd and Mg–3Y alloys (wt.%) were studied by advanced acoustic technique and electron microscopy. Particularly, a contribution of rare earth metals on the microstructure and resulting mechanical properties is addressed with respect to the extrusion direction. The extrusion of both investigated alloys was performed with the same processing parameters. Thus, the differences in initial microstructures and textures is caused by alloying elements. Consequently, deformation behavior of investigated alloys significantly depended on both the content of the alloy and mutual orientation of extrusion direction and deformation axis due to texture. The activity of individual deformation mechanisms during loading was elucidated using the acoustic emission (AE) technique including advanced adaptive sequential k-means (ASK) algorithm analysis. The results of the AE analysis were related to microstructure evolution provided by the electron backscatter diffraction (EBSD) technique, including Schmid factor analysis. The obtained results had shown that activity of the basal slip system was predominantly affected by the texture, whereas the activity of non-basal slip systems and twinning was dependent on both texture and type of rare earth metal in the alloy.

International audience; In the present article, metallic nanoparticles (NPs) used as nanogauges and electron backscattered diffraction (EBSD) are combined to investigate deformation mechanisms of the UR45 N duplex steel. The kinematic fields bring precious details in the evolution of the local deformation of austenitic and ferritic phases. The crystallographic information at the initial stage and in the plastic domain is obtained by the EBSD technique. Strain evolutions in each phase are analyzed. The first strain marks appear in austenite just before the elastoplastic transition. Slip and twinning activities in austenite constitute an important part of the work hardening of the material. The slips in ferrite are visible in the plastic domain and present complex geometry. The role of phase boundaries, which act as strain barrier is highlighted. The incompatibilities of deformations between the two phases modify the deformation mechanism of austenite in comparison with a pure austenitic stainless steel as 316 L. Local interactions between phases during the deformation are analyzed. The strong strain heterogeneities in the plastic domain are analyzed in the kinematic fields. Local evolutions of the deformation are also confronted to the macroscopic behavior of the material.

Microstructures of high-strength bainitic steels were quantitatively analyzed using EBSD analysis based on transformation behavior and morphological characteristics. According to multiple linear regression analysis, reliable empirical equations to predict yield ratio and uniform elongation were proposed. From the results, the fraction of the granular bainite and polygonal ferrite microstructure were estimated to be the most influential factors on the yield ratio and uniform elongation of high-strength bainitic steels, respectively.

For finding a process for improving the strength of single crystal Cu while still maintaining good plasticity and electrical conductivity, the die with an internal angle (Ф) = 105° and an outer curvature angle (ψ) = 37°was used to prepare the equal channel angular pressing (ECAP) deformation by route Bc. The deformation behavior of single crystal copper during ECAP was investigated through electron backscatter diffraction (EBSD), optical microscope (OM) and X-ray diffraction (XRD). The mechanical properties and electronic conductivity after deformation were tested. The results show that the texture evolution is {111} (intital)→ {111} → {111} → {112} during 4 passes deformation. The tensile strength and the hardness of single crystal copper increased 123% and 115% respectively after four passes, the electrical conductivity has no obvious decrease. This result indicates that ECAP method can significantly improve the strength of single crystal copper, simultaneously, the plasticity and conductivity of the material remains at an excellent level.

A Cr–Mn–Ni–N series high strength metastable austenitic stainless steel (14Cr10Mn) was used to investigate the effect of cold rolling reduction on mechanical properties at various low testing temperatures. Microstructures of tested samples were observed by transmission electron microscope (TEM) and electron back scatter diffraction (EBSD) at the gauge section. The experimental results show that the size of the rib-like α′- martensite formed during tensile testing is sensitive to temperature but insensitive to cold rolling reduction. The results also show that tensile strength is more sensitive to temperature than yield strength, while the effect of cold rolling is completely opposite. The cold rolling inhibits the martensite transformation kinetics of the tensile process after promoting it at a certain temperature condition, and the promotion effect reaches a maximum value approximately 4% when the cold rolling reduction is 10%. However, it also suppresses the α′- martensite content finally formed during tensile testing due to the high stress-strain state when the cold rolling reduction exceeds 10%, while a larger cold reduction promotes the production of α′- martensite. In addition, lowering temperature can effectively promote the formation of e-martensite at the end of the Stage I of work hardening, and becomes a transitional phase of subsequent transformation to α′- martensite, which directly leads to the enhancement of strength in the stage II of work hardening.

Hot deformation behavior of equiatomic FCC CoCuFeMnNi complex concentrated alloy has been investigated via isothermal compression tests on Gleeble-3800 thermo-mechanical simulator in the temperature (T) range of 1073–1273 K and strain rate ( e ˙ ) range of 1–10−3 s−1. This has been aided with detailed microstructural analysis using SEM, EBSD and TEM to decipher the deformation micro-mechanisms during hot compression tests. The processing maps have been constructed by superimposition of the instability map with efficiency map and the optimum thermo-mechanical processing conditions were found to be T = 1173 K, e ˙ = 10−3 s−1 and T = 1273 K, e ˙ = 10−2 s−1. Microstructural investigation using SEM and EBSD reveal phase separation between Cu-rich and Cu-lean regions wherein Cu-rich FCC phase at the grain boundaries undergoes discontinuous dynamic recrystallization (DDRX) while the Cu-lean phase undergoes dynamic recovery (DRV). The average activation volume in the range of 44–250 b3 suggest that cross slip is the rate controlling mechanism during the deformation and activation energy of 394 kJ/mol, that is almost twice than that for diffusion in copper, indicate contribution from both mechanical and thermal component to the overall activation energy. It is evident that the diffusion assisted copper segregation aids in obtaining higher efficiency of deformation and easy processability due to a unique microstructure comprising of Cu-lean grains surrounded by soft Cu-rich grains near grain boundaries which undergo DDRX. Numerical simulations using finite element method are able to correctly predict hot deformation behavior, establishing the processing-microstructure-property paradigm in CoCuFeMnNi complex concentrated alloy.

In this study, the work-hardening behavior of Ag microwires with different grain sizes has been investigated, and the results show that the work-hardening rate of Ag microwires does not decrease with the increase of grain size, suggesting that the work-hardening capacity of Ag microwires is insensitive to grain size. Moreover, the microstructure evolution of the samples before and after tensile tests has been characterized using scanning electron microscope-backscattered electron (SEM-BSE), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). As a typical low stacking faults energy (SFE) material, stacking faults and twins are particularly easy to form in Ag microwires. Abundant stacking faults and twins, as well as minor lattice orientation adjustment in Ag microwires were observed and confirmed to play key roles on their grain-size insensitive work-hardening capacity. The current study provides insights for manufacturing Ag microwires for bonding process and other microelectronics applications.

In the present study, low-cost high-entropy Al(5,10)Cr12Fe35Mn (28,23)Ni20 alloys containing 5 and 10 at. % Al were designed based on the thermodynamic principles. The chemical compositions of the studied high entropy alloys (HEAs) were selected to obtain face centered cubic solid solutions with good cold deformability. The alloys were produced using arc melting and were subsequently subjected to cold rolling to reduce their thickness up to 90%, to study their structure stability and strengthen them. Elemental mapping of the as-cast and deformed structures was conducted using electron microprobe analysis. Subsequently, the mechanical properties of the as-cast and heavily deformed alloys were determined using micro hardness measurements and tensile and compression tests. The microstructure evolution was studied using X-ray diffraction and electron backscatter diffraction. It was observed that the thermodynamic parameters of HEAs could be used to enhance their mechanical properties, and the experimental results were in agreement with those observations. After substituting Mn with Al in Al5Cr12Fe35Mn28Ni20, the yield stress of Al10Cr12Fe35Mn23Ni20 increased by ∼14%. Moreover, the alloy maintained good cold workability and its tensile ductility exceeded 40%. Cold rolling the alloy to 90% increased its yield stress more than four times. Despite the heavy deformation caused by cold rolling (2.3 true strain), deformation twinning was induced in these alloys.

The study focuses on the significant effects of carbon and alloying elements on variant selection during martensite transformation and its influence on toughness. 0.17C steel with low content of alloying elements and 0.13C steel with relatively higher alloying content were studied. The strength of quenched 0.13C steel was inferior to 0.17C steel, and their yield strengths were 894 and 999 MPa, respectively. However, −40 °C Charpy impact energy of 0.17C and 0.13C steels was 40 and 198 J, respectively. An analysis by electron backscattered diffraction (EBSD) underscored that a larger proportion of V1/V2 variant pairs and a lower content of V1/V4 variant pairs in 0.13C steel reduced the residual stress, thereby significantly enhancing the toughness of steel. In addition, the high density of high angle grain boundaries (HAGBs, especially V1/V2 variant pairs) had the ability to hinder crack propagation, which further toughens the matrix.

Two types of material positions, with AZ31 or AM60 in retreating side, were used for dissimilar friction stir welding in this study. The appearance, microstructure evolution, mechanical properties and fracture mechanism of the joints were investigated. The results showed that significant microstructure evolution occurred in the joint under the intense stirring and thermal cycling. Furthermore, the material positions had little influence on the appearance, tensile properties and failure locations of the joints. It is interesting that all the tensile joints fractured at the boundary of thermo-mechanically affected zone (TMAZ)/nugget zone (NZ) near the AZ31 side. In order to explore the fracture mechanism of the joints, the relationship of failure locations, microstructure and texture evolution of joints were analyzed. The analysis on EBSD demonstrated that the texture evolution in both TMAZ and NZ, as well as a certain extent of dislocation density and strain existing adjacent to TMAZ/NZ interface, was the main factor leading to the fracture at the boundary of TMAZ/NZ. The tensile strength of AZ31 alloy was smaller than that of AM60, the grain gradient and the second phases size near the NZ/TMAZ interface of AZ31 side were larger than those of AM60, resulting in the fracture tending to AZ31 side.

A technical process concept, i.e., controlling recrystallization degree, was proposed and performed in order to manufacture the medium Mn steels overcoming discontinuous yielding and low yield-to-tensile ratio. Based on this, a plain medium Mn steel with 8.9 wt % Mn content was used in view of retarding recrystallization due to relatively high Mn content. The mechanical properties of the studied steel were evaluated by uniaxial tensile test at room temperature, and the detailed characterization of microstructural evolution was performed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the recrystallization process of the cold-rolled plates with 50% or 70% rolling reduction during ART annealing was effectively controlled, resulting in a desired mechanical behavior, i.e., high yield-to-tensile ratio, continuous yielding and outstanding combination of strength and ductility. This is because a certain proportion of deformed grains are retained due to incomplete recrystallization, which retains a higher density of mobile dislocation. This concept can be suggested to be quite suitable for the manufacturing of medium Mn steel using continuous annealing process, in which heating temperature and time can be controlled flexibly.

Recent researches on the addictive manufacturing (AM) of titanium alloys have shown the significant advantages in fabricating complex constructions. Laser deposition manufacturing (LDM) and selective laser melting (SLM) are two representative AM technologies, Ti-6Al-4V alloy samples for the complex structure and functional integration application were fabricated by LDM-SLM hybrid manufacturing process in present research. The microstructure of LDM-SLM hybrid fabrication Ti-6Al-4V components can be divided into three regions: LDM zone mainly composed of the α laths, SLM zone which is fully α' martensitic and a large number of irregular crystals are distributed in the bonding area between the LDM zone and SLM zone, which is named heat affect zone (HAZ). The inhomogeneous microstructure leads to the discrepancy in mechanical behavior, after multiple cyclic thermal treatment at 750 °C/10min↔960 °C/10min, the original α′ martensitic is complete converted to the mixture of α-phase and β-phase and the growth of the thick α laths was restrained. The microstructure and mechanical properties of LDM zone and SLM zone tend to be equivalent at all of cycle-treatement. After cyclic thermal treatment, the strength of LDM samples and hybrid fabricated samples vary slightly, but the plasticity of LDM is improved significantly. The morphology features of α phase and evolutions of crystallographic orientation are the dominant factors of microstructure homogenizations during cyclic thermal treatments, related information was found in the EBSD investigation.

This paper studied the plastic deformation behaviour of DP600 steel subjected to uniaxial tension, by means of in-situ EBSD technique. It provides experimental evidences and detailed insight into the microstructural aspects of plastic deformation. A phase identification method based on the band slope map of EBSD was adopted to differentiate martensite from ferrite. The results show that the plastic strain localization lies mainly in the ferrite grains, fracture could usually start in ferrite grains close to hard martensite grains. With the increase of strain, average misorientation angle decreased while the fraction of LAGBs increased. Average Taylor factor for the whole microstructure became higher at high strains due to work hardening process, and plastic deformation results in soft regions with zonal distribution parallel to the loading direction. In the undeformed state, the texture orientation ( 111 ) [ 0 1 ¯ 1 ] and ( 111 ) [ 1 1 ¯ 0 ] are the major components of the γ-fibre while ( 223 ) [ 1 1 ¯ 0 ] and ( 221 ) [ 1 1 ¯ 0 ] are the main components of α-fibre. The intensity of the α-fibre slightly decreased, while the intensity of the γ-fibre increased with increasing strain. Plastic deformation occurred in some grains which were subdivided into different regions due to the activation of different slip systems. The tensile axis orientation of the grain rotated gradually to the line link − , and lattice rotation within one single grain differs from regions to regions.

Laser metal deposition (LMD) is a common manufacturing technique of laser additive manufacturing (LAM) which belongs to coaxial powder feeding method. The LMDed SS304 specimens are fabricated by the same combination of the process parameters so that they have the similar properties. The microstructure is similar to that of the selective laser melted (SLMed) specimen. The grain sizes of the LMDed specimen are compared with those of the specimens manufactured by the traditional method and SLM. Through the calculation of Ni and Cr equivalents in the LMDed SS304 specimen and the analytical results of electron backscattered diffraction (EBSD) and energy dispersive spectroscope (EDS), the phase compositions of the LMDed SS304 specimen are evaluated. The hardness of the LMDed specimen is compared with that of the conventionally manufactured wrought SS304 and SLMed specimens. And due to the differences of the grain size and phase composition on the different directions, the hardness of the LMDed specimen is anisotropic. The static tensile properties (ultimate tensile strength (UTS), yield strength (σ0.2) and elongation (EL)) and fatigue strength (FS) of the LMDed specimen are compared with those of the specimens made by the traditional method and SLM. The S N curve is established by the multiple experiments. Scanning electron microscopy (SEM) is applied to observe the fracture morphology of the static tension and tension-compression fatigue tests. And EDS is applied to analyze the chemical compositions of the particles on the fracture surface. As expected, LMD has the higher static tensile properties and fatigue strength than those of the specimen manufactured by the traditional method.

2060 and 2099 are both newly developed high-strength aluminum-lithium (Al-Li) alloys for fuselage panels of jetliners. In this work, double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Al-Li alloys was performed using AA4047 filler wire under optimized parameters. Weld zone microstructure and T-joint mechanical properties were investigated by means of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), nano-indentation and in-situ tensile test. Experimental results indicated that the equiaxed grain zone (EQZ) featured by dense large-angle (θ＞10°) grain boundaries was observed in the weld zone along the fusion lines. Besides the softening problem found in the partially melted zone (PMZ), local softening phenomenon was detected in the local enrichment region of the EQZ. During in-situ tensile tests, the crack was initiated at the weld toe and then propagated alternately in the PMZ and EQZ's local enrichment regions. Micro-voids induced the localized softening problem and the crack's intergranular expansion in the EQZ. Localized absence of silicon was most likely to cause continuous micro-voids in the EQZ.

In this article, we probe the strain partitioning between the microstructural features present in a continuously cooled carbide-free bainitic steel together with damage nucleation and propagation. These features mainly comprise of phases (bainitic ferrite, martensite, and blocky/thin film austenite), interfaces between them, grain size and grain morphology. A micro Digital Image Correlation (μ-DIC) technique in scanning electron microscope is used to quantify the strain distribution between these microstructural features. The results show a strong strain partitioning between martensite, bainitic ferrite and retained austenite that provides weak links in the microstructure and creates conditions for the crack initiation and propagation during deformation. Blocky austenite islands accommodate maximum local strains in the global strain range of 0–2.3% and undergo strain-induced austenite to martensite transformation governing the local strain evolution in the microstructure. However, the local strains are minimum in martensite regions during entire in-situ deformation stage. Narrow bainitic ferrite channels in between martensitic islands and martensite-bainitic ferrite interfaces are recognised as primary damage sites with high strain accumulation of 30 ± 2% and 20 ± 3% respectively, at a global strain of 9%. The inclination of these interfaces with the tensile direction also affects the strain accumulation and damage.

The hydrogen embrittlement behavior of multilayer steel consisting of 7 alternating layers of martensitic (MART) steel and twinning-induced plasticity (TWIP) steel was investigated through variation in the ratio of the hard layer to the soft layer, and the size of the grains according to the autenization temperature. Multilayer steels with a high fraction of MART was predicted to be vulnerable to hydrogen embrittlement, but was found to be less susceptible to hydrogen embrittlement due to the presence of a TWIP layer, which is supported in the center of the multilayer steels. In addition, when the grain size is large, twinning in the TWIP layer and subdivision in the MART layer occur, and so hydrogen embrittlement is promoted due to the trapping of hydrogen. The effect of electrochemically-charged hydrogen on the multilayer steel during deformation was analyzed using electron backscatter diffraction in terms of the microstructure-mechanical property relationships.

The mechanical properties and microstructure transformation of Cu Cr Zr alloys obtained by upward continuous casting with varying Zr contents were studied by optical microscopy (OM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) after cold drawing with different strain and heat treatment. The results show that good strength can be obtained through cold drawing with suitable heat treatment. The peak tensile strength can achieve 587.8 MPa and the peak yield strength can reach 499.6 MPa; The difference of yield strength of Cu Cr Zr alloy during cold drawing deformation becomes larger with the increase of Zr element content when the strain gradually improves; The increase of the Zr element will promote the recrystallization of the alloy at aging after cold drawing, refining the crystal grains. It contributes about 70% of the increase in strength, act as a fine grain strengthening effect, increasing the strength of the alloy.

Hot workability, which indicates the ability of metallic materials to be deformed at elevated temperatures, is generally governed by the microstructure-dependent strength and ductility. In this work, the influence of three types of pre-precipitation microstructure, tailored through different cooling conditions (i.e., air cooling, water quenching and furnace cooling) after heat treatment, on hot workability in an Al-Cu-Mg-Zr alloy was studied by means of constitutive analysis, processing maps and microstructure characterizations using scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. The results showed that pre-precipitation microstructure had a considerable influence on flow stress, hot deformation activation energy, dynamic softening and hot workability. The highest flow stress accompanied by a more notable dynamic softening was shown in the water-quenched alloy, whereas the flow stress in the furnace-cooled alloy was the lowest. The flow stresses of air-cooled, water-quenched and furnace-cooled alloys could be described well by the hyperbolic sine equation with hot deformation activation energies of 180.5, 298.9 and 161.5 kJ/mol, respectively. Dynamic softening mechanisms were found to be associated with different contributions of dynamic recovery, dynamic precipitation and/or dynamic recrystallization in various tempers of the present alloy. Further, the air-cooled alloy showed minimal instability regimes and an optimal pre-precipitation microstructure for hot forming. The deteriorated hot workability in the water-quenched alloy was attributed to dynamic precipitation effects. However, coarse constituent phases in the furnace-cooled alloy were easily broken during deformation under a higher strain rate, which led to deformation instability.

In situ synchrotron X-ray diffraction was used to track real-time austenite reversion in AISI 201 austenitic stainless steel deformed to a true strain of 0.34 under tensile testing. The deformed material was continuously annealed from 100 °C up to 800 °C at a heating rate of 0.05 °C s−1. Phase changes and microstrain partitioning were evaluated by means of the direct comparison method and modified Williamson-Hall plots, respectively. The microstructure of the deformed steel consists of γ, e- and α′-martensite with volume fractions of 0.24, 0.07, and 0.69, respectively. e → γ reversion occurs within the temperature range of 150–400 °C through a shear mechanism. The starting (As) and finishing (Af) temperatures for α’ → γ reversion are 486 °C and 770 °C, respectively. Three stages were distinguished for this reaction. By evaluating the crystallite size of both γ- and α′-phases, it can be inferred that α' → γ reversion is diffusion-controlled. Such results were corroborated by thermodynamic simulations to assess the driving force for γ-formation. Microstructural aspects such as γ-nucleation sites, in-grain misorientation, grain refinement, and crystallographic texture were investigated by means of electron backscatter diffraction. Fresh formed ultrafine austenite grains hold different crystallographic orientations than those of untransformed austenite.

Microstructural evolutions during hot deformation and annealing of alumina-forming austenitic (AFA) steel were investigated using electron backscatter diffraction (EBSD). Tensile properties of deformed and as-received AFA steels were also tested. The yield strength and ultimate tensile stress of deformed AFA steel increase gradually with the increase in rolling reduction, while the fracture elongation decreases rapidly. Specifically, after hot-rolling with the reduction of 40%, the yield strength of the annealed specimen is high to 773.2 MPa, and the fracture elongation of this sample is about 43.6%. The excellent mechanical properties can be attributed to the smaller average grain, larger Schmid factor and coincident site lattice (CSL) boundaries. Such a rapid decline of the elongation of AFA steel occurs due to increasing low angle grain boundaries (LAGB, 15°).

This study investigated stress corrosion cracking (SCC) nucleation in sensitized austenitic stainless steel from the viewpoint of grain boundary (GB) character and strain at a GB where SCC can nucleate. Prior to SCC testing, normal and shear strains were measured on the surface of a specimen subjected to an initial strain of 1% via the digital image correlation (DIC) technique. Then, SCC testing was conducted under a constant load corresponding to the initial strain in a tetrathionate solution. After testing, crystal orientations in the specimen surface were measured by the electron backscattered diffraction (EBSD) technique. The relationship among crack initiation sites, GB character measured by EBSD, and strains measured by DIC is discussed. Stress corrosion cracks were found to be mainly initiated at random large-angle boundaries. The sites of intergranular crack initiation were characterized using the maximum normal strain along GBs, while the shear strain did not affect the crack initiation.

This paper studies the effects of high-pressure torsion (HPT) at ambient temperature on microstructural evolution and mechanical properties enhancement in pure copper. The aim is to introduce gradient microstructure, with various statistical distributions of grain size and grain orientations to examine their effect on strength and ductility. To this end, extruded cylindrical pure copper subjected to HPT for 1, 2, and 3-turns resulted in grain refinement down to the grain size of 500 nm. Combination of microhardness test and EBSD scans through the radial direction confirm the creation of a heterogeneous structure through the thickness and radial directions. The results demonstrate that increasing the shear strain leads to (1) ultra-fine grain (UFG) generation at deformed coarse-grain boundaries, (2) an increase in the fraction of recrystallized grains and high angle grain boundaries, and (3) a homogenous structure in the last step. A unique mixture has been obtained due to the particular shape of the anvils. The mixture included a chain of UFGs and coarse grains contain dislocations and subgrains. The highest level of gradient structure through the thickness was observed after 1-turn, which leads to the best combination of strength and ductility.

The through-silicon via (TSV) approach is crucial for three-dimensional integrated circuit (3-D IC) packaging technology. However, there are still several challenges in the TSV fabrication process. One of the widely known challenges is via protrusion phenomenon. Annealing a TSV wafer makes the copper (Cu) TSVs under high stress and may form a protrusion where the Cu is extruded out of the TSV structure. The phenomenon occurs because of the large mismatch in the coefficient of thermal expansion between Cu via and silicon (Si) layer. Cu protrusion is able to cause crack, delamination of the back-end-of-line and short circuit of the chip, thus, it is a dangerous threat to the metal layer interconnect. Experiments are conducted to characterize the protrusion using several techniques. Scanning electron microscope is used to observe the protrusion topography and measure the height. Electron backscatter diffraction (EBSD) technique is implemented to study the grain size distribution, local texture and microstructure evolution inside Cu vias. For the experiment, arrays of 10 μm diameter TSVs are fabricated and annealed in argon gas environment in six different temperatures. In this paper, finite element analysis (FEA) is carried out to study the Cu protrusion under different annealing conditions. Correlation between numerical results and experimental data is then performed. Based on the verified FEA methodology, several parametric studies are then conducted, including the effects of annealing temperature on Cu protrusion, residual stress distributions of TSV structures. The simulation results are helpful to understand and solve the key problem in TSV fabrication process and reliability challenge.

A β-solidified nearly lamellar γ-TiAl ( α 2 + γ ) based alloy was investigated to understand the evolution of microstructure during hot isothermal compression test at 1050 °C (below eutectoid). Cylindrical samples were compressed to different true strains up to 60%. The deformed samples were then characterized using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) to understand the active deformation mechanisms. Dynamic flow softening behavior, i.e., dynamic recrystallization (DRX) type flow was observed. While no new strain induced phases were observed, there were minor changes in the phase fractions as a function of strain. Kinking and bending of lamellae at certain areas in the microstructure of compressed samples were predominant. Preliminary analysis by TEM indicated the presence of twinning in both γ and β phases.

Surface modification is an essential process route to improve the fatigue performance of aerospace components. Microstructural evolution in Ni-based superalloy Udimet720Li processed by deep cold rolling (DCR) was investigated experimentally using X-Ray diffraction, electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Deep cold rolling produces hardened surface due to a range of microstructural changes associated with grain refinement, low angle grain boundaries (LAGBs) formation, and pile-up of dislocations around γ ' precipitates and across twin boundaries. The defect structures within the deformed subsurface comprised of equiaxed and elongated dislocation cells at grain boundaries, mutual interactions of slip bands, slip bands- γ ' precipitate at grain boundaries and multi-variant modes of twinning. The plastic deformation is predominantly driven through slip and dislocation multiplication mechanism during DCR. Surface compressive residual stresses, FWHM, micro-hardness, the fraction of LAGBs and the depth of plastically strained region increased with DCR hydrostatic pressure. These fundamental understanding on process-microstructure-property could provide a deep insight into the fatigue crack initiation mechanism of surface modified Ni-based superalloys.

Two dual phase steels with varying martensite content (∼ 10 and 33%) have been deformed in tensile mode at various strain rates (0.001–800/s). The microstructural parameters after deformation have been studied in detail using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The minute details of deformation features within the ferrite matrix have been investigated using EBSD based misorientation analysis. The influence of metallurgical parameters like ferrite grain size and its spatial distribution, the size and fraction of martensite on the deformation at different strain rates have also been investigated along with evolution of crystallographic texture. It has been found that strain rate influences the gradient in deformation in the ferrite grains between the interface and the grain interiors. Increase in martensite although enhances the dislocation density in the ferrite grains, but it also restricts the rotational ability of ferrite, which led to restricted sub-structural recovery at high strain rates. By observing the misorientation development ahead of the interphase boundaries, the failure mechanisms of these dual phase steels have been explained.

In this study, single and multi-step aging treatments (SAT and MAT) following a super-solvus solution treatment were employed to tailor the mechanical property of a prototypical powder metallurgy (PM) nickel-based superalloy. Vickers hardness and tensile test at room temperature were used to evaluate the mechanical properties after different heat treatments. Microstructural evolution after heat treatments and tensile tests were revealed through scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) techniques. Our results show that the MAT with a stabilization at 650 °C for 24 h between the solution and aging assists to achieve the highest strength corresponding to microstructure of bimodal distribution of γ’ precipitates. The associated mechanism for variation in microstructures and mechanical properties are discussed based on thermodynamic calculations and precipitation strengthening theory. In addition, an empirical relationship between Vickers hardness and tensile strength of nickel-based superalloys is examined which is believed to be assistance for rapid evaluating mechanical response of materials with different microstructures.

The ultrafine-grained structure developed here after severe plastic deformation of Al-Mg and Al-Mg-Sc-Zr by equal channel angular pressing (ECAP) and cold rolling (CR) is presented to consist of dense dislocation walls and cell structure of dimension of ~ 300 nm. Detailed characterization by traditional transmission electron microscopy (TEM), electron backscattered diffraction (EBSD) and X-ray diffraction (XRD) has been carried out to reveal microstructure evolution during deformation and annealing. A unique bimodal grain structure, which consists of ultrafine grains (less than 150 nm) and fine grains (in the range of 200–500 nm) having high dislocation density, was developed after 16 ECAP passes and CR. It was also found that microstructure inhomogeneity exits even after high ECAP passes and annealing at high temperature (280 °C) for 1 h. High yield strength (YS) of ~ 550 MPa and tensile strength (TS) of ~ 560 MPa were obtained after 16 ECAP passes and CR, however, the corresponding elongation dropped to ~ 8.2%. Subsequent optimum annealing was found to be 240 °C × 1 h, by which comprehensive mechanical properties were maintained (~ 481 MPa for YS, ~ 512 MPa for TS and ~ 13.7% for elongation) in Al-Mg-Sc-Zr (16 ECAP passes). The reasons of inhomogeneous microstructure and the origins of high strength, i.e. high solute Mg content, dense dislocations, ultrafine grains and nanoscale Al3(Sc, Zr) particles are discussed.

Super304H, which is an austenitic heat-resistant steel, was aged at 650 °C for up to 5000 h. Its microstructural evolution during aging was observed by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD). The precipitate evolution in the aged specimens was analyzed by both X-ray diffraction (XRD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) and selected area electron diffraction (SAED). In addition, the precipitation kinetics of M23C6 carbide was established. Hardness and impact tests were performed on the aged specimens. Finally, the relationship between the mechanical properties and microstructural evolution was revealed. After aging, Super304H steel exhibited the same fine grains as in the as-received condition with a Cu-rich phase, secondary Nb(C,N) precipitates inside the grains, and M23C6 carbides mainly at grain boundaries. The Cu-rich phase and the secondary Nb(C,N) precipitated in specimens aged for 500 h; this leads to a marked increase in hardness. Precipitation of the Z phase also occurred in the aged Super304H steel. M23C6 carbides precipitated rapidly during aging, with content approaching 90% of the saturated content in specimens aged for 5000 h. The reduction in impact toughness in Super304H steel was found to be associated with the precipitation of the M23C6 carbide, which is similar to that in the HR3C steel. However, the deterioration was much less significant as compared to HR3C steel because of the discontinuous distribution of carbides at grain boundaries due to the fine grain size.

The formation of submicron structural defects within austenite (γ), e- and α′-martensite during cold rolling was followed in a 17.6 wt.% Mn steel. Several probes, including XRD, EBSD, and ECCI-imaging, were used to reveal the complex superposition of the strain hardening mechanisms of these phases. The maximum amount of e-martensite is observed at a strain of e = 0.11. At larger strains, the amount of e decreases suggesting that it precedes the α′-formation (γ → e → α′). Stacking faults and twins are the main planar defects noticed in e-martensite. The remaining γ is finely subdivided by stacking faults and twins up to e = 0.22. From e = 0.51 on, twinning and multiplication of dislocations are the principal strain hardening mechanisms in austenite. Deformation is accommodated in α′ by the rearrangement of dislocation tangles into dislocation cells plus shear banding at e = 1.56. During cold rolling, austenite develops a Brass-type texture component, which can be associated to mechanical twinning. e-martensite presents its basal planes tilted ∼24° from the normal direction towards the rolling direction. The α′-martensite develops and strengthens both, the bcc α- and γ-texture fibers during cold rolling.

A novel technology combining forming and reaction synthesis has been developed to manufacture NiAl alloy sheet components which are difficult to form using conventional fabrication approaches. A semi-circular shaped NiAl sheet component was successfully fabricated using forming-reaction synthesis integrated process (FRSIP) with laminated Ni/Al foils. Through microstructure characterization, the mechanism of the reaction synthesis of laminated Ni/Al foils was studied for manufacturing homogenous components. The process was performed at 650 °C under the pressure of 15 MPa for 4 h to consume Al layers and produce the multilayered composite of Ni/Ni2Al3/Ni, and further annealed at 1200 °C under the pressure of 25 MPa for 1 h to produce fully dense and homogeneous NiAl alloy. Based on electron back-scatter diffraction (EBSD) analysis, the NiAl sheet contains inter-laminated coarse-grain layers (CGLs) and fine-grain layers (FGLs), which formed at original Al foil layers and original Ni foil layers, respectively. The grain sizes of the CGLs can be adjusted by controlling the thickness of the original Ni foils. The mechanical properties of NiAl sheet were studied by means of nano-indentation tests and tensile tests, which showed that the weak grain boundary weakened the Hall-Patch (H-P) phenomenon. The bimodal grain structure was a main factor influencing the performance of plastic deformation at high temperature.

Adiabatic shear deformation behaviors in cold-rolled copper under different impact loading directions were systemically investigated in this paper. Split Hopkinson Pressure Bar (SHPB) system was used for the dynamic test. The microstructure and microtexture of the received shear localization regions were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD) technique and microhardness tests. Three hat-shaped specimens were cut from cold-rolled copper sheet with the direction with an angle of 0° (RD sample), 45° (RD-45° sample) and 90° (TD sample) from the rolling direction within the rolling plane. The stress-strain curves indicate that the mechanical properties of the cold-rolled copper sheet show regularity in the work hardening dominated stage and that the shear stress of TD sample is the highest in that of the those three. OM results show that the morphology of adiabatic shear band in three samples shows differences that their deformation processes fall into two categories, pure relative shearing in RD sample and relative shearing with rotation in RD-45° and TD sample. EBSD results reveal that ultrafine grains with high-angle-boundaries are found within the adiabatic shear bands in three samples. The microhardness measurements show that the microhardness of shear region in three samples are significant higher than that of other regions. However, the size of grains within the shear band in RD sample are much larger than that in the other two samples. Microtexture analysis reveals that the grain orientations inside the shear band in three samples show similar characteristics that the direction tends to parallel to the local shear direction and the {111} and {100} planes tend to parallel to the local shear plane. The calculated results show that rotational dynamic recrystallization can take place in the shear band.

An analysis of the fatigue behavior of rolled AZ31 magnesium alloy through numerical simulations of polycrystalline aggregates using the crystal plasticity finite element method is presented. A phenomenological pseudo-slip model including twinning, detwinning and subsequent slip in the twinned region was considered in this study. It was calibrated against uniaxial monotonic and cyclic experiments on rolled AZ31 Mg alloy. Multiple periodic two-dimensional synthetic microstructures were generated based on morphological and crystallographic data obtained from electron backscattering diffraction (EBSD) measurements. Fatigue simulations were conducted at different stress amplitudes and mesoscopic non-local fatigue criteria for slip-induced and twin-induced crack initiation were investigated. It was observed that basal slip and twinning-detwinning are the main deformation mechanisms taking place during cyclic loading but that these deformation modes generally occur in different grains. The comparison of the investigated criteria with experimental data also revealed that the twin-induced criterion exhibit better trends in terms of mean behavior, relative dispersion and stress amplitude sensitivity compared with the slip-induced criterion. Finally, the predictive capabilities and limitations of the current modeling approach are discussed.

The plastic anisotropies of two hot-rolled Lean Duplex Stainless Steels (commercially known as LDX 2101 and LDX 2404) were investigated by applying compressive strains, at 10−3 s−1 rate, along the rolling- and transverse-directions (RD and TD). The microstructural changes were elucidated by Electron Backscatter Diffraction (EBSD) as a function of strain level and loading direction. In both alloy grades, the austenite phase shows a weaker texture development than the ferrite phase; the later develops {001} and {110} textures in LDX 2101 and LDX 2404 alloys, respectively. Also, in both alloys, the yield stress along the TD is larger by 10% than along the RD. Anisotropies are also detected in the rate of property changes with deformations; after 30% true strain, the flow stress along the RD in LDX 2101 alloy starts exceeding the stress along the TD. Microstructural studies indicate that the load partitioning, grains shape, phase boundaries and austenite to martensite phase transformations are the origins of the anisotropic phenomena in LDX 2101 alloy, whereas the crystallographic texture of ferrite phase, phase boundaries and load partitioning are the plausible origins of plastic anisotropies in LDX 2404 alloy.

Quenching and partitioning (Q&P) steels have been attracted much attention due to excellent combination of strength and ductility. However, the actual Q&P microstructures may contain the carbon-depleted martensite (i.e., initial martensite, M1), bainitic ferrite (BF), secondary martensite (M2) and retained austenite (RA). Hence, it is challenging to build a quantitative model of the yield strength of Q&P microstructures, since it requires prior knowledge of the yield strength of each constituent phase that is not always in a clear state in Q&P microstructures. In the present work, based on the analysis with respect of microstructural heterogeneities inevitably existing during martensitic transformation, both as-quenched and Q&P microstructures are simplified and regarded as a mixture of α′ phase (containing M1, M2 or BF) and γ phase (RA). The carbon content, dislocation density and substructure size of the α′ phase and γ phase were measured by SEM, EBSD and XRD. Then we build two generalized physical models to predict the yield strength of as-quenched and Q&P steels with the carbon content in range of 0.06–0.42 wt%. The physical models show the yield strength of α′ phase varies as the reciprocal of the square root of the block width (Hall-Petch relation), but varies as the inverse of the lath thickness (Langford-Cohen relation). The deviation analysis indicates that the assumption and simplification with regard of microstructure do not greatly affect the accuracy of the prediction of yield strength for both as-quenched and Q&P steels, with uncertainty less than 10%. The effect of carbon content and microstructural features on the yield strength of as-quenched and Q&P steels was discussed in terms of the developed physical models. It reveals that the residual carbon atom in α’ phase is still the dominant factor controlling the yield strength of Q&P steels, despite of possible highly uneven carbon distribution.

The effects of welding thermal cycles on the mechanical properties of a high strength, high ballistic resistance 10 wt pct Ni steel were studied. Welding simulations were performed using a Gleeble 3500 thermal-mechanical simulator to replicate microstructures observed in the heat-affected zone of this steel, which is a transformation induced plasticity or TRIP steel. The microstructural influences on austenite content, strength, and toughness were determined using a variety of characterization techniques including XRD, SEM, EBSD, and STEM/EDS. The results demonstrate that with increasing peak temperature of the welding thermal cycle, the amount of austenite present in the microstructure decreases. However, the toughness results do not directly correlate with the austenite contents. Poor toughness is observed in the intercritical heat-affected zone as a result of brittle high carbon martensite in this region. This region represents the greatest challenge in terms of maintaining high ballistic resistance of welds of 10 wt pct Ni steel. These results are significant in that the toughness of this steel is not solely based on the austenite content, which would be expected given it is a TRIP steel, but instead is a function of other microstructural influences.

High-pressure torsion (HPT) processing was applied to an Fe-10Ni-7Mn (wt.%) martensitic steel at room temperature and the grain size was reduced from an initial value of ~5.5 μm to an ultrafine value of ~185 nm for the ferritic phase and around 30 nm for the austenitic phase after 20 HPT turns. The microstructure and mechanical properties of the as-processed material were evaluated using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), field emission scanning electron microscopy (FESEM), microhardness measurements and tensile testing. In addition, annealing of an as-processed specimen was analyzed by differential scanning calorimetry (DSC). The results show that HPT processing increases the hardness and ultimate tensile strength to ~690 Hv and ~2230 MPa, respectively, but the ductility is decreased from ~16.5% initially to ~6.4% and ~3.1% after 10 and 20 turns, respectively. The hardness distributions and EBSD images show that a reasonably homogeneous microstructure is formed when applying a sufficient level of pressure and torsional strain. The DSC results demonstrate that processing by HPT reduces the start and finish temperatures of the reverse transformation of martensite to austenite and there is continuous re-crystallization after the recovery process.

In the present study the effect of initial texture and annealing temperature on the microstructure and mechanical anisotropy of pure magnesium has been investigated. Evolution of microstructure after annealing was analysed by optical microscopy and SEM/EBSD. Magnesium samples with different initial textures were deformed at room temperature at a strain rate equal to 10−3 s−1 followed by subsequent annealing at 473 K and 673 K. The texture evolution, work hardening and microstructure have been examined after annealing treatment. It was found that the initial texture affects the main deformation mode as well as influences the texture upon annealing. During compression, samples deform by twinning, while slip becomes the dominant deformation mode for samples having c-axis perpendicular to the extrusion direction. Moreover, it was shown that the recrystallization temperature is critical for texture evolution and mechanical properties of the annealed magnesium samples. Annealing at 473 K does not initiate recrystallization in samples exhibiting twins whereas samples without twins undergo recrystallization strengthening particular texture components in ODF sections. However, annealing at 673 K leads to a strong grain growth lowering the yield strength of the material. It was shown that an intensive twinning can stabilize the microstructure of pure magnesium and improves its mechanical properties up to 473 K.

The mechanical behavior of a metastable β titanium alloy, Ti-2Al-9.2Mo-2Fe (wt%), was studied through high compression strain rate (~3000 s−1) at ambient temperature by Spilt Hopkinson Pressure Bar (SHPB) tests after solution treatment at 850 ℃ for 0.5 h and 950 ℃ for 1 h. The mechanism of deformation and microstructure evolution was investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Multiple deformation mechanisms, including primary and secondary {332} twinning, stress-induced martensite, and stress-induced ω-phase and dislocation slips, were identified in specimens subjected to solution treatment at 850 ℃ for 0.5 h. In contrast, only primary and secondary {332} twinning and dislocation slips were detected in specimens subjected to solution treatment at 950 ℃ for 1 h. The athermal ω precipitation produced after solution treatment and elevated temperature generated during dynamic loading played a crucial role in the different deformation mechanisms observed in the two different specimens. Moreover, the deformation mechanisms active during plastic deformation in the different strain regimes affected the development of different textures in the Ti-2Al-9.2Mo-2Fe alloys from each regime.

Deformation twinning in a mild steel is investigated under quasi-isentropic compression (IC) and shock compression (SC) to about 12 GPa, as regards the effects of pulse duration (plateau width) and strain rate (rising edge slope), and associated twin strengthening. The pulse duration ranges from 80 ns to 790 ns; and two rise times are explored, approximately 30 ns for SC and 300 ns for IC. Free-surface velocity histories are measured to obtain strain and strain rate. The postmortem samples are characterized with electron backscatter diffraction, and the yield strengths of the samples pre-deformed by impact are examined with a materials testing system. For SC, twin density and size increase with pulse duration up to 580 ns. At longer pulse durations, the increase in twin density is stagnated as a result of deviatoric stress relaxation, while twin size continues growing. For IC (410 ns), twin density and size are much larger than the SC counterpart, as a result of shallower rising edge. Increased deformation time can compensate the effects of reduced strain rate or applied stress for deformation twinning. Twin strengthening effect is strong in postmortem samples, depends on twin density instead of area fraction, and follows the empirical Hall–Petch relationship.

Local mechanical properties of Ti-6Al-4V butt joints produced by friction stir welding (FSW) were investigated using the shear punch testing and correlated with the global mechanical properties, microstructure, and microtexture evolution of the joint. The conditions for obtaining defect-free joints, under high heat input conditions were determined for the investigated alloy. The shear punch results revealed important differences in yield and ultimate strength between the base material (BM), the heat affected zone close to the BM (HAZ1), the heat affected zone close to the nugget (HAZ2) and two distinct regions in the stirred zone (SZ1 and SZ2). Electron microscopy examination indicated that the microstructure of the BM was converted from equiaxed and elongated α grains with an average size of about 20 µm and a basal transverse texture to a very fine, less than 1 µm diameter, equiaxed microstructure at the center of the SZ, while bimodal structures with lamellar and equiaxed grains were found elsewhere. The analysis of the local mechanical properties indicated that HAZ1 had the lowest mechanical properties of the joint and the obtained results are interpreted in terms of transition texture evolution from the BM to the HAZ using misorientation analysis of high resolution EBSD maps.

The high-temperature deformation of an Mn-Al alloy with a chemical composition of Mn51Al47C2 was assessed using hot compression testing at the temperature range of 600–800 °C and the strain rates ranging 0.001 s−1 to 1 s−1. Optical microscopy (OM), scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and X-ray diffraction (XRD) analyses were implemented to characterize the samples. It was found that during deformation, the τ phase dynamically transformed into γ2+ β + e phases and the transformation temperature reduced from the equilibrium value of about 790 °C down to

AlSi10Mg alloy was fabricated by Selective Laser Melting (SLM) using two different atmospheres, argon and nitrogen, both in vertical and horizontal built directions. The influence of work environment and anisotropy are studied in this work by keeping all other process parameters including shielding gas pressure constant. The meso-structural features revealed scan tracks and melt pool layers while the microstructural features have showed cellular structure with α-Al matrix and its boundary made up of the eutectic mixture of Al and Si. These cells were approximately of 500 nm size as revealed by TEM analysis. The grain morphology and texture were studied using EBSD analysis. The XRD analysis revealed similarity in the phases formed in samples built under argon and nitrogen environment. Both the horizontal as well as vertical built samples contain elongated grains with 〈 100 〉 direction oriented along the built direction and 〈 100 〉 fibre texture in the XY plane. Tensile test results showed the maximum strength of 385 ± 5 MPa was exhibited by vertically built sample under nitrogen environment while the lowest strength of 338 ± 2 MPa was exhibited by horizontally built sample under argon environment. Surface roughness and porosity measured in all the conditions exhibited minor variation in the average surface roughness and porosity area fraction values. Among the samples tested under same built orientation, the variation in strength is approximately 5% higher in nitrogen environment while among the samples tested under same working environment, the variation in strength is approximately 7.5% higher in vertically built samples. This states that the influence of working environment on strength is lesser than that of the built orientation. The materials exhibited brittle failure with inclined fracture profile, fracture morphology with pores, river patterns and inter-cellular fracture plus approximately 4.5% elongation in all the tested samples, implied isotropic elongation behaviour. The samples built under both the work environments exhibited the similarity in defect structure, microstructure and nearly isotropic behaviour in mechanical properties. It inferred that nitrogen could be preferred over argon as shielding gas in SLM for its cost effectiveness.