Search

Additive manufacturing has witnessed significant growth in recent years, revolutionizing the automotive and aerospace industries amongst others. Despite the use of additive manufacturing for creating complex geometries and reducing material consumption, there is a critical need to enhance the mechanical properties of manufactured parts to broaden their industrial applications. In this work, AISI 316L stainless steel is used to fabricate parts using three different strategies of the additively manufactured Laser Powder Bed Fusion (LPBF) technique, i.e., continuous, alternate, and island. This study aims to identify methods to optimize grain orientation and compaction support provided to the material under load, which influence the frictional and wear properties of the manufactured parts. The load-bearing capacity is evaluated by measuring the frictional and wear properties. The wear patch track is also examined to establish the physical mechanisms at the surface interface that lead to the smooth transition in response to the load. Grain orientation is compared across different strategies using Electron Backscatter Diffraction (EBSD) maps, and the influence of surface roughness on sliding behavior is also evaluated. The results demonstrate that the island scanning strategy yields the best performance for load-bearing applications, exhibiting superior grain orientation and hardness in the additively manufactured parts. [ABSTRACT FROM AUTHOR]

This study investigates the anisotropic grain growth of Fe-doped aluminum titanate ceramics using Electron Backscatter Diffraction (EBSD). Three grades of materials exhibiting various grain size distributions were prepared on the basis of different sintering conditions. The crystal structure of the raw powder was first refined using X-ray diffraction. Then the microstructure variation of sintered polycrystalline aluminum titanate associated to anisotropic grain coarsening was accurately studied. Due to the orthorhombic structure of β -Al 2 TiO 5 , the crystal shape is prismatic and elongated along the [100] direction. This specific grain shape is analyzed in relation with crystallographic axes in the frame work of the Wulff approach. The obtained results provide valuable information regarding the microstructure of such flexible ceramics made off anisotropic grains. [ABSTRACT FROM AUTHOR]

This study investigates tensile deformation, damage analysis, and the effect of microtexture on a 10 % vol. zirconia particle-reinforced TRIP steel composite. In situ tensile tests and simulations were conducted, with sequential SEM images captured during tensile loading tests and electron backscatter diffraction (EBSD) providing initial crystal orientation data. SEM images were utilized in digital image correlation (DIC) analysis to calculate the local plastic strain distribution using VEDDAC software. Initial micrographs and EBSD data were transformed into geometry files for simulations, employing crystal plasticity with a dislocation density-based model and a newly proposed phase field approach-based ductile-brittle damage criterion for both austenite and ceramic particles. MATLAB's image processing functions were used to compare and validate experimentally observed damage instances with simulation predictions. The effect of microtexture combined with various physical quantities was explored using MTEX. The results show that the simulations accurately predict strain concentration around ceramic particles, with a higher strain observed in the middle region compared to the DIC observations. The simulated strain in the austenitic matrix is found to be 1.4 times higher than the DIC measurements. Quantitative analysis of damage pixels reveals that the proposed critical plastic strain value aligns closely with experimental results, showing an error of - 0.25 % compared to 1.121 % for a smaller strain case. This comprehensive analysis provides insight into the effect of microstructural attributes on material performance and behavior under tensile deformation, leading to a validated microstructural-informed damage-inclusive crystal plasticity model.

The microstructure and uniformity of Cu metallization in the through glass via (TGV) structure were investigated through electron backscatter diffraction (EBSD) analysis system and finite element analysis (FEA) method. Two different direct current (DC) electroplating methods were employed for the TGV metallization, including single- and multiple-step electroplating methods. We found that the multiple-step electroplating process with appropriate current density (j)/plating time (t) can efficiently enhance the throwing power (TP) value (uniformity) of electroplated Cu in the TGV metallization. Moreover, the Cu electrodeposition via the multiple-step electroplating process possessed larger grain sizes and high fraction of high angle grain boundaries (HAGBs), including twin boundaries (TBs), which are very beneficial to the mechanical and electrical properties of Cu interconnects. Detailed analyses of the uniformity (i.e., TP), crystallographic microstructure (e.g., grain size), and mechanical characteristics (e.g., ductility) of electroplated Cu derived from single- and multiple-step electroplating process were discussed in this paper.

To explore the optimal hot ductility regimes of a low-carbon bearing duplex stainless steel, we conducted tensile tests using a Gleeble 3500 simulator within a temperature range spanning from 900 °C to 1250 °C and a strain rate of 10 s−1, mimicking industrial conditions. Analysis of mechanical properties revealed the presence of three distinct zones, each intricately linked to microstructural variations. Employing thorough two-dimensional (2D) characterization enabled detailed crack analyses, unveiling a decrease in crack density with rising temperatures. Interestingly, precipitation effects only became prominent at higher temperatures, contrasting with δ/γ interface decohesion as the primary cause of cracking at lower temperatures. Subsequent three-dimensional (3D) analyses corroborated these observations. Large-area (>1 mm2) electron backscatter diffraction (EBSD) mappings, along with grain orientation spread (GOS) analyses, shed light on dynamic recrystallization (DRX) and dynamic recovery (DRV) mechanisms in both ferrite and austenite phases. Contrary to prevailing theories, our findings suggest the coexistence of DRX and DRV for both phases. Notably, at higher deformation temperatures, DRX prevails in both ferrite and austenite, whereas at lower temperatures, DRV becomes more dominant in austenite, leading to strain buildups in austenite and strain incompatibility between δ/γ interfaces. The identification of a critical temperature at 1100 °C underscores the vulnerability of δ/γ interfaces to crack formation, potentially compromising the material's workability. These insights deepen our understanding of hot ductility behaviour in low-carbon bearing duplex stainless steel, offering valuable guidance for industrial applications and process optimization.

This study introduces a novel method for integrating aluminum flexible printed circuit boards (FPCBs) and copper FPCBs into battery management systems (BMS) using and instantaneous large area facial laser source soldering. Achieving a robust bonding strength of 65 MPa involved applying 600 W of laser power for 2 s, enhancing atom diffusion and promoting intermetallic compound (IMC) growth. Finite Element Method (FEM) simulations revealed variations in heat transfer between Al and Cu, affecting IMC thickness at interfaces. Formation of the (Cu, Ni)3Sn4 phase within solder, and variations in laser output significantly influenced solder joint orientation and Al electrode nucleation. Excessive laser power (>800 W) caused critical damage, such as delamination at the Al-PI interface, altering fracture modes and bonding strength. Furthermore, with a detailed examination of the laser soldering phenomenon through both experimental and numerical investigations, this study provides a thorough understanding of the different soldering mechanisms in conventional reflow soldering compared to instantaneous uniform large-area heat source laser soldering. These insights provide new design and material considerations to replace the conventional wiring harness with Al/Cu FPCB lap joints which optimize the circuitry and reducing BMS volume.

The present investigation is dealing with the evolution of simultaneous dynamic and metadynamic recrystallization (DRX)& (MDRX) phenomena by physical simulation for a 4-strock hot compression process, where flow curves were presented for each stroke. The primary alloy is a penetrator steel containing 0.3% C in addition to some Cr, Mo, Ni and 1.63 W. Calculated grain size after the onest of DRX & occurrence of MDRX decreases continuously with the increase of cumulative strain reaching to 0.289 µm. However, Electron Backscatter Diffraction (EBSD) investigation established that 99% of the grains, after the last compression stroke, were detected as <1.0 μm, with an average grain size 0.31 μm. Microstructure after simulation presents fine lath martensitic structure, coexisting with Cr-W carbides, which are crammed at the inter- martensite laths. Furthermore, 56% of the grains showed grain boundaries misorientation creating High Angle Grain Boundaries (HAGB), which are promoting MDRX. The flow curve of each stroke definitely contains two complementary microstructure events, namely a DRX, and a MDRX phenomenon, where the peak stress (σp) of DRX is inversely proportional to the mean temperature of stroke. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

n this study, an innovative algorithm is developed to transform microstructures to hierarchical graphs without manual feature engineering. The hierarchical graph comprises two layers. Initially, pixel data, which includes Euler angles, phase, and position, forms the pixel-wise graphs within individual grains. Following this foundation, the grains serve as nodes, constituting the second layer. Importantly, the hierarchical graph preserves essential measurement data and structural details for training machine learning models. After that, a contrastive learning model based on hierarchical graph is designed to capture representations of microstructures obtained by the electron backscatter diffraction (EBSD) technique. This model can be directly extended for other microscopy techniques, such as Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), and Transmission Electron Microscopy (TEM). Using the learned microstructure representations, an autoencoder model for the directed energy deposition (DED) is developed to establish the relationship among process parameters, microstructures, and material properties, completing the process-structure–property cycle quantitatively. The performance of the present model is naturally benchmarked against two other models: a contrastive learning model based on pixel-wise graph (without manual feature engineering) and a contrastive learning model based on grain-wise graph (employing manual feature engineering). The results of the present model highlight the potential in decoding the process-structure–property relationships in the DED process.

Low-angle grain boundaries (LAGBs) accommodate residual stress through the rearrangement and accumulation of dislocations during cold rolling. This study presents an electron wind force-based annealing approach to recover cold-rolling induced residual stress in FeCrAl alloy below 100 °C in 1 min. This is significantly lower than conventional thermal annealing, which typically requires temperatures around 750 °C for about 1.5 h. A key feature of our approach is the athermal electron wind force effect, which promotes dislocation movement and stress relief at significantly lower temperatures. The electron backscattered diffraction (EBSD) analysis reveals that the concentration of low-angle grain boundaries (LAGBs) is reduced from 82.4% in the cold-rolled state to a mere 47.5% following electropulsing. This level of defect recovery even surpasses the pristine material's initial state, which exhibited 54.8% LAGBs. This reduction in LAGB concentration was complemented by kernel average misorientation (KAM) maps and X-ray diffraction (XRD) Full Width at Half Maximum (FWHM) measurements, which further validated the microstructural enhancements. Nanoindentation tests revealed a slight increase in hardness despite the reduction in dislocation density, suggesting a balance between grain boundary refinement and dislocation dynamics. This proposed low-temperature technique, driven by athermal electron wind forces, presents a promising avenue for residual stress mitigation while minimizing undesirable thermal effects, paving the way for advancements in various material processing applications. [ABSTRACT FROM AUTHOR]

In a thermoelastic martensitic transformation, there is a “self-accommodation” in which the microstructure itself relieves strain induced by the transformation. In this study, the crystal structure and self-accommodation microstructure of martensite in Ti30Ni50Zr20 alloy were investigated using X-ray diffraction, scanning electron microscopy with electron backscatter diffraction, and transmission electron microscopy. In addition, the deformation microstructure was investigated by observing the samples after tensile tests. The crystal structure of the martensite in the Ti30Ni50Zr20 alloy was determined to be the B19′ monoclinic structure. In this alloy, plate- and polygonal-like variants with a width of a few microns were observed, and pairs of habit-plane variants (HPVs) forming {011}B19′ twins were observed at the interface. The self-accommodation has a mosaic-like morphology because of the combination of these pairs of HPVs. The (001)B19′ compound twins were formed as internal defects. These twins are considered to be lattice-invariant shear (LIS) of martensite in this alloy. No plateau region was observed in the tensile test. In the deformed specimen, the self-accommodation was collapsed by the movement of the HPV interface and the introduction of (100)B19′ compound twins was observed as an internal defect. This defect is considered to be not LIS but a deformation twin. The lack of a plateau region in the stress–displacement curve was attributed to these deformed microstructures. [ABSTRACT FROM AUTHOR]

Quantifying the intrinsic properties of 2D materials is of paramount importance for advancing their applications. Large‐scale production of 2D materials merits the need for approaches that provide direct information about the role of growth substrate on 2D material properties. Transferring the 2D material from its growth substrates can modify the intrinsic properties of the asgrown 2D material. In this study, suspended chemical vapor deposition (CVD) graphene films are prepared directly on their growth substrates in a high‐density grid array. The approach facilitates the quantification of intrinsic strain and doping in suspended CVD graphene films. To achieve this, transmission electron microscopy and large‐area Raman mapping are employed. Remarkably, the analysis reveals consistent patterns of compressive strain (≈−0.2%) both in the diffraction patterns and Raman maps obtained from these suspended graphene films. By conducting investigations directly on the growth substrates, the potential influences introduced during the transfer process are circumvented effectively. Consequently, the methodology offers a robust and reliable means of studying the intrinsic properties of 2D materials in their authentic form, uninfluenced by the transfer‐induced alterations that may skew the interpretation of their properties. [ABSTRACT FROM AUTHOR]

The microstructural phases in steel influence the magnetic moments due to different alignments and arrangements of the atoms in the crystal lattice. This study is based on the relationship of the microstructural phases with saturation magnetization (MS), a characteristic magnetic property of a phase in a material. Understanding the changes in microstructural phases during steel processing is paramount for different industries to fulfill the desired mechanical properties of the grade. The current research investigates the microstructural phases and magnetic properties of industrial‐grade high‐carbon steel under compressive and controlled‐thermal deformation to obtain a dual‐phase steel microstructure, i.e., retained austenite and martensite. High‐carbon steel samples are subjected to compression and heat treatments, resulting in different variations of dual‐phase structure. The sample microstructure is characterised using optical microscopy, and scanning electron microscopic analyses, and their phases are quantified using X‐ray diffraction, complemented by electron back‐scatter diffraction techniques. An empirical relationship between the microstructural phases of steel and the magnetic characteristics is derived based on the magnetic measurements determined using a SQUID magnetometer. The correlation statistically holds good for high‐carbon steels. This relationship between the volume of transformation of retained austenite (VRA) to martensite (VM) and the magnetic properties is successful in investigating the possibility of a non‐destructive method for evaluating dual‐phase low‐alloyed high‐carbon steels. [ABSTRACT FROM AUTHOR]

The ability of high-entropy alloys (HEAs) for hydrogen storage is a rather new topic in the hydrogen community. HEAs with the C14 Laves phase have shown a high potential to reversibly store hydrogen at room temperature, but most of these alloys require a high-temperature activation treatment. This study explores the role of interphase boundaries on the easy activation of HEAs at room temperature. Two chemically similar HEAs with single and dual phases, TiV 1.5 ZrCr 0.5 MnFeNi (C14 + 4 vol% BCC phases) and TiV 1.5 Zr 1.5 CrMnFeNi (single C14 phase), are designed and synthesized. While the dual-phase alloy readily absorbs hydrogen at room temperature without any activation treatment, the single-phase alloy requires a high-temperature activation. It is suggested that interphase boundaries not only provide pathways for easy hydrogen transport and activation of HEAs at room temperature but also act as active sites for heterogeneous nucleation of hydride. This study introduces interphase-boundary generation as an effective strategy to address the activation drawback of HEAs. • The interphase boundary effect on hydrogen storage in high-entropy alloys (HEAs) is studied. • Two septenary HEAs are designed for room-temperature hydrogen storage. • The BCC/C14 interphase boundaries ease activation of HEAs for hydrogen storage. • Easy activation is due to mainly fast hydrogen transport via interphase boundaries. [ABSTRACT FROM AUTHOR]

In order to study the corrosion resistance of 904L super austenitic stainless steel welded joints in a simulated nuclear power plant tertiary loop water environment, the Kelvin probe force microscope (KPFM), electron backscatter diffraction (EBSD), electrochemical experiments and immersion corrosion experiments were used. These methods were employed to investigate the influence of the characteristic distribution of grain boundaries of welds and base materials, surface contact potential difference and medium temperature on the corrosion resistance of 904L welded joints and base metal. Results showed that the 904L base metal had higher Σ3 special grain boundaries and exhibited better corrosion resistance than the weld. The average potential differences on the surfaces of the weld and the weld fusion line were 318 mV and 295 mV, respectively, and a potential difference valley existed in the local area, which exhibited higher electrochemical activity. The critical pitting temperatures (CPT) of the base metal and the weld were 50 ℃ and 43 ℃, respectively, CPT Weld

Additive manufacturing has witnessed significant growth in recent years, revolutionizing the automotive and aerospace industries amongst others. Despite the use of additive manufacturing for creating complex geometries and reducing material consumption, there is a critical need to enhance the mechanical properties of manufactured parts to broaden their industrial applications. In this work, AISI 316L stainless steel is used to fabricate parts using three different strategies of the additively manufactured Laser Powder Bed Fusion (LPBF) technique, i.e., continuous, alternate, and island. This study aims to identify methods to optimize grain orientation and compaction support provided to the material under load, which influence the frictional and wear properties of the manufactured parts. The load-bearing capacity is evaluated by measuring the frictional and wear properties. The wear patch track is also examined to establish the physical mechanisms at the surface interface that lead to the smooth transition in response to the load. Grain orientation is compared across different strategies using Electron Backscatter Diffraction (EBSD) maps, and the influence of surface roughness on sliding behavior is also evaluated. The results demonstrate that the island scanning strategy yields the best performance for load-bearing applications, exhibiting superior grain orientation and hardness in the additively manufactured parts.

In this study, the microstructural behavior of the advanced Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn-0.15Si (VT8M-1) alloy during rotary swaging (RS) was investigated. VT8M-1 has increased heat resistance and is considered a replacement for the Ti-6Al-4V alloy. It was shown that, during RS, the evolution of the primary a phase is characterized by the formation of predominantly low-angle boundaries according to the mechanism of continuous dynamic recrystallization. The density of low-angle boundaries increases three times: from 0.38 µm−1 to 1.21 µm−1 after RS. The process of spheroidization of the lamellar (a + b) component is incomplete. The average size of globular a and b particles was 0.3 μm (TEM). It is shown that the microstructures after RS (ε = 1.56) and equal-channel angular pressing (ECAP) (ε = 1.4) are significantly different. The temperature–velocity regime and the predominance of shear deformations during ECAP contributed to a noticeable refinement of the primary a-phase and a more complete development of globularization of the lamellar (a+b) component. EBSD studies have shown that RS leads to the formation of a structure with a higher density of low- and high-angle boundaries compared to the structure after ECAP. The results are useful for predicting alloy microstructure in the production of long rods that are further used in forging operations. [ABSTRACT FROM AUTHOR]

Through large area crystallographic analysis across the whole cross-section of a 0.5 mm zinc wire by backscattered electron diffraction (EBSD) excavated by plasma focused ion beam (pFIB) and topographic analysis by scanning electron microscopy (SEM), the crystallographic and topographic characteristics of corrosion on zinc are identified and correlated. Striated domains dominating the surface are the result of preferential dissolution of non-basal planes leaving (0001) plates intersecting the surface. Remnant fragments of zinc lie close to the original surface which is due to the combined effects of the initial protective film on the surface and the crystallographic corrosion. Three corrosion layers were found, namely from the outside inwards, a highly porous outer layer, a densified intermediate layer and an attacked layer. [ABSTRACT FROM AUTHOR]

Abstract Quantifying the intrinsic properties of 2D materials is of paramount importance for advancing their applications. Large‐scale production of 2D materials merits the need for approaches that provide direct information about the role of growth substrate on 2D material properties. Transferring the 2D material from its growth substrates can modify the intrinsic properties of the asgrown 2D material. In this study, suspended chemical vapor deposition (CVD) graphene films are prepared directly on their growth substrates in a high‐density grid array. The approach facilitates the quantification of intrinsic strain and doping in suspended CVD graphene films. To achieve this, transmission electron microscopy and large‐area Raman mapping are employed. Remarkably, the analysis reveals consistent patterns of compressive strain (≈−0.2%) both in the diffraction patterns and Raman maps obtained from these suspended graphene films. By conducting investigations directly on the growth substrates, the potential influences introduced during the transfer process are circumvented effectively. Consequently, the methodology offers a robust and reliable means of studying the intrinsic properties of 2D materials in their authentic form, uninfluenced by the transfer‐induced alterations that may skew the interpretation of their properties.

In this study, the effects of differences in grain size, grain boundary type and misorientation on the initiation of discontinuous precipitates are investigated for the Cu–5Ni–1.25Si alloy. Samples with different grain sizes are obtained by thermomechanical treatment, and the smaller the grain size, the higher the percentage of discontinuous precipitate at the same aging time, while there is no significant difference in the growth rate of the reaction front of discontinuous precipitates. EBSD is used to study the effect of grain boundary misorientation on discontinuous precipitates, the characteristics of discontinuous precipitates initiation on different grain boundaries are investigated by multivariate statistical analysis. It is found that discontinuous precipitates only initiate from random grain boundaries instead of coincident site lattice boundaries, where random grain boundaries with misorientation angles of 30–50° are more prone to discontinuous precipitates. And the initiation of DPs at different misorientation axes is different. There is a clear borderline for the axes such as , , and . The grain boundaries below this borderline do not initiate DP, while all grain boundaries below this angle initiate DPs. The cases for axes such as , , and are more complicated. On these misorientation axes, grain boundaries with lower or higher misorientation angles do not initiate DPs, while grain boundaries at intermediate range misorientation angles do initiate DPs.

Multi axial forging (MAF) is a forging-based severe plastic deformation (SPD) technique which is prominently used to refine grain structure and improve the strength of the material. While the advantages of MAF lie in its simple tool design and ability to process bulk materials, the main limitation is the inhomogeneity in the generated microstructure across the cross-section at initial passes. Increasing the number of MAF passes may partially help to solve the problem, but arbitrary increase in the number of passes may lead to redundant increase in manufacturing cost and time. The current work proposes a manufacturing strategy for MAF to achieve homogeneous microstructure with uniform grain refinement by using reduced number of MAF passes. To achieve structural uniformity within fewer MAF passes, a controlled thermo-mechanical based optimum MAF process strategy is developed on a commercial pure Al through the finite element analysis (FEA) simulation and the same is validated experimentally. The manufacturing strategy resulted significant grain refinement via simultaneous action of continuous dynamic recrystallization and geometric dynamic recrystallization with microstructural homogeneity which caused a significant improvement in tensile properties (more than two times than the base) with considerable ductility (more than 25%) and isotropy property across the thickness. The scientific knowhow has been established via processing–structure–property correlation-ship.

Compression tests were conducted at room and cryogenic temperatures to investigate the low-temperature plasticity in Mg–3Al–1Zn alloy. The strain to failure and fracture strength in Mg–3Al–1Zn alloy increase by 21.4% and 51.6% from room to cryogenic temperature. Using a quasi-in-situ EBSD method, it is found that {10 1¯ 2} tension twins dominate at room temperature, while abundant (10 1¯ 2)-(01 1¯ 2) twin-twin interactions are observed at cryogenic temperature. Multiple slips, including pyramidal and basal slips, occur in twin-twin interactions, enhancing the strain to failure and flow stress at cryogenic temperature. The high dislocation density near twin-twin interactions boundaries would contribute to the high hardening rate and flow stress at cryogenic temperature. This work would provide a novel way to enhance plasticity in magnesium alloys and gain an in-depth understanding of twin-twin interactions.

This study investigates the effectiveness of combined thermal and athermal stimuli in mitigating the extremely high-density nature of dislocation networks in the form of low-angle grain boundaries in FeCrAl alloy. Electron wind force, generated from very low duty cycle and high current density pulses, was used as the athermal stimulus. The electron wind force stimulus alone was unable to remove the residual stress (80% low-angle grain boundaries) due to cold rolling to 25% thickness reduction. When the duty cycle was increased to allow average temperature of 100 °C, the specimen could be effectively annealed in 1 min at a current density of 3300 A/mm2. In comparison, conventional thermal annealing requires at least 750 °C and 1.5 h. For specimens with 50% thickness reduction (85% low-angle grain boundaries), the electron wind force was again unable to anneal the defects even at 3300 A/mm2 current density and average temperature of 100 °C. Intriguingly, allowing average concurrent temperature of 200 °C eliminated almost all the low-angle grain boundaries at a current density of 700 A/mm2, even lower than that required for the 25% thickness reduced specimens. Comprehensive electron and X-ray diffraction evidence show that alloys with extremely high defect density can be effectively annealed in less than a minute at approximately 200 °C, offering a substantial improvement over conventional high-temperature annealing.

In this study, we investigated the anisotropy in tensile deformation behaviour of CP-Ti plate in the rolling (RD) and transverse direction (TD), using in-situ SEM-EBSD testing and stress-relaxation method. The EBSD-assisted slip trace analysis was conducted to examine the slip systems activated within individual grains. It was found that the prismatic slip is dominant in the RD sample, whilst the activity of non-prismatic slip systems is higher in the TD sample. The slip transfer significantly occurred in the TD sample, thereby promoting the activity of multiple slips and dislocation interactions at the grain interiors. However, the limited occurrence of slip transfer in the RD sample indicates the strong dislocation pinning at the grain boundaries (GBs). Combined with the EBSD analysis, the SEM observations revealed that the GBs with ledge character are formed in the slip-favourable and -unfavourable grain pairs, and the GBs with sink character are created in the grain pairs whose c-axes are equally inclined to the loading direction, but the sign of c-axis inclination angles is opposite with each other. The formation of GB ledges and GB sinks was pronounced in the RD and TD sample, respectively. The GB-dislocation interactions and GB-mediated deformation arising from the orientation relationship between the particular grain pairs led to the anisotropy in strain-hardening behaviour of polycrystalline α-Ti.

By means of direct current electrodeposition, Cu foil with columnar grain growth and equiaxed grain growth with different average grain sizes were prepared. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscope (TEM) were employed to elucidate the correlation between the microstructures and properties of Cu foil after a certain relaxation time under different grain growth methods. A remarkable preferential ratio of {220} orientation was exhibited in the columnar-grown copper. However, as the copper layer transitions to equiaxed grain growth, the superiority altered to {200} crystal orientation. This variability in grain orientation makes the copper layer profile of columnar crystal growth higher than that of equiaxed crystal formation. The twin boundary density in copper foil increases as the grain growth mode changes from columnar to equiaxed, and grain refinement is beneficial to increase the twin boundary density in the samples. And columnar crystal copper and equiaxed crystal copper show different twin characteristics. There are a few single-stage twin steps in columnar crystal copper and more multi-stage twin steps in equiaxed crystal copper. With an increase of twin boundary density, both the tensile strength and the ductility increase remarkably.

This work was undertaken to evaluate the influence of friction-stir welding (FSW) under a high-heat input condition on microstructural evolution. Given the extreme combination of deformation conditions associated with such an FSW regime (including the highest strain, temperature, and strain rate), it was expected to result in an unusual structural response. For this investigation, a commercial 6013 aluminum alloy was used as a program material, and FSW was conducted at a relatively high spindle rate of 1100 rpm and an extremely low feed rate of 13 mm/min; moreover, a Ti-6Al-4V backing plate was employed to reduce heat loss during welding. It was found that the high-heat-input FSW resulted in the formation of a pronounced fine-grained layer at the upper weld surface. This observation was attributed to the stirring action exerted by the shoulder of the FSW tool. Another important issue was the retardation of continuous recrystallization. This interesting phenomenon was explained in terms of a competition between recrystallization and recovery at high temperatures. Specifically, the activation of recovery should reduce dislocation density and thus retard the development of deformation-induced boundaries. [ABSTRACT FROM AUTHOR]

Multi axial forging (MAF) is a forging-based severe plastic deformation (SPD) technique which is prominently used to refine grain structure and improve the strength of the material. While the advantages of MAF lie in its simple tool design and ability to process bulk materials, the main limitation is the inhomogeneity in the generated microstructure across the cross-section at initial passes. Increasing the number of MAF passes may partially help to solve the problem, but arbitrary increase in the number of passes may lead to redundant increase in manufacturing cost and time. The current work proposes a manufacturing strategy for MAF to achieve homogeneous microstructure with uniform grain refinement by using reduced number of MAF passes. To achieve structural uniformity within fewer MAF passes, a controlled thermo-mechanical based optimum MAF process strategy is developed on a commercial pure Al through the finite element analysis (FEA) simulation and the same is validated experimentally. The manufacturing strategy resulted significant grain refinement via simultaneous action of continuous dynamic recrystallization and geometric dynamic recrystallization with microstructural homogeneity which caused a significant improvement in tensile properties (more than two times than the base) with considerable ductility (more than 25%) and isotropy property across the thickness. The scientific knowhow has been established via processingestructureeproperty correlation-ship. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) is an innovative technique that is used to enhance the fatigue strength of structural materials via the generation of significant residual stress. The present work was undertaken to evaluate the degree of plastic strain introduced during LSP and thus improve the fundamental understanding of the LSP process. To this end, electron backscatter diffraction (EBSD) and nano-hardness measurements were performed to examine the microstructural response of laser-shock-peened Ti-6Al-4V alloy. Only minor changes in both the shape of α grains/particles and hardness were found. Accordingly, it was concluded that the laser-shock-peened material only experienced a small plastic strain. This surprising result was attributed to a relatively high rate of strain hardening of Ti-6Al-4V during LSP. [ABSTRACT FROM AUTHOR]

This work is part of a wide-ranging study aiming to enhance the technology of dissimilar friction-stir welding of aluminum and titanium. In the previous study, a new approach was proposed that provided an exceptionally narrow intermetallic layer. However, an essential disadvantage of this technique was the significant material softening in the aluminum part. Hence, the present work was undertaken in order to obtain insight into microstructural processes and material flow in the aluminum part. To this end, the stop-action technique was applied. It was found that the microstructural evolution included several stages. Specifically, the initial material underwent the discontinuous static recrystallization in the heat-affected zone. With the approach of the rotating tool, the recrystallized grains experienced continuous dynamic recrystallization, which resulted in grain refinement. The subsequent transportation of material around the rotating tool provided no significant alterations in microstructure. This "superplastic-like" character of material flow was attributed to a dynamic balance between grain refinement and grain coarsening. It was also found that the stirred material experienced a secondary deformation induced by the rotating tool shoulder far behind the welding tool. The concomitant microstructural changes were most pronounced at the upper weld surface and gave rise to a fine-grained layer. [ABSTRACT FROM AUTHOR]

Low-angle grain boundaries (LAGBs) accommodate residual stress through the rearrangement and accumulation of dislocations during cold rolling. This study presents an electron wind force-based annealing approach to recover cold-rolling induced residual stress in FeCrAl alloy below 100 °C in 1 min. This is significantly lower than conventional thermal annealing, which typically requires temperatures around 750 °C for about 1.5 h. A key feature of our approach is the athermal electron wind force effect, which promotes dislocation movement and stress relief at significantly lower temperatures. The electron backscattered diffraction (EBSD) analysis reveals that the concentration of low-angle grain boundaries (LAGBs) is reduced from 82.4% in the cold-rolled state to a mere 47.5% following electropulsing. This level of defect recovery even surpasses the pristine material’s initial state, which exhibited 54.8% LAGBs. This reduction in LAGB concentration was complemented by kernel average misorientation (KAM) maps and X-ray diffraction (XRD) Full Width at Half Maximum (FWHM) measurements, which further validated the microstructural enhancements. Nanoindentation tests revealed a slight increase in hardness despite the reduction in dislocation density, suggesting a balance between grain boundary refinement and dislocation dynamics. This proposed low-temperature technique, driven by athermal electron wind forces, presents a promising avenue for residual stress mitigation while minimizing undesirable thermal effects, paving the way for advancements in various material processing applications.

The purpose of this work was the examination of microstructural evolution during the fabrication of an Al/Al2O3 composite by friction stir processing (FSP). In order to obtain new insight into this process, a longitudinal section of the produced composite was studied, and advanced characterization techniques (including electron backscatter diffraction and microhardness mapping) were applied. It was found that the reinforcing particles rapidly rearranged into the "onion-ring" structure, which was very stable against the subsequent dispersion. Specifically, the remnants of the comparatively coarse-scale particle agglomerations have survived even after 12 FSP passes. Therefore, it was concluded that three or four FSP passes, which are often applied in practice, are not sufficient to provide a homogeneous dispersion of the reinforcing particles. It was also revealed that the gradual distribution of the nanoscale Al2O3 particles throughout the aluminum matrix promoted a subtle reduction in both the portion of high-angle boundaries and the average grain size. These observations were attributed to the particle pinning of grain-boundary migration and dislocation slip. [ABSTRACT FROM AUTHOR]

Interstitial Free (IF) steels are nowadays commonly used for stamping complex parts of outer automotive bodies. Current requirements for fast production lead to the need of monitoring the real state of the material after stamping based on its real material conditions. It is desirable to describe and quantify the evolution of microstructure deformation and plastic conditions before and after the stamping process. This paper presents Electron Backscatter Diffraction analyses of deformed and non-deformed IF steel, including the quantitative measurement of the localized plastic response of the real stamped part, using an unconventional indentation method. The effect of strain rate was evaluated using the highspeed tensile tests. The increased ratio of the Low Angle Grain Boundaries was found as a good parameter to quantify the depletion of plasticity.

This research studies the hot deformation behavior of cast and extruded AZ80 magnesium alloys for forging applications. Uniaxial hot compression tests were carried out at a temperature of 400 °C and strain rates ranging from 0.001 to 0.1 s−1, to various strain levels up to a true strain of 1. Detailed microstructure and texture characterizations of the deformed samples were performed using electron backscatter diffraction and x-ray diffraction techniques. The results show that multiple dynamic recrystallization (DRX) mechanisms were simultaneously active in both starting materials at all the tested deformation conditions, resulting in significant grain refinement. Cast and extruded samples showed the development of a similar microstructure, texture, and flow stress by a strain of 1, despite having very different starting microstructures. This was investigated by considering differences in DRX mechanisms and kinetics, and relative deformation mode activities. Since industrial forgings typically involve strains much higher than 1, comparable final microstructure and texture are expected in industrial-scale forgings of AZ80 at 400 °C, irrespective of the starting material state. [ABSTRACT FROM AUTHOR]

Based on the method of friction stir surface processing (FSSP), the Nip/H63 modified surface layer was obtained by adding nickel particles (Nip) to the H63 copper alloy surface. The microstructure, electron backscatter diffraction (EBSD), electrochemical properties, and surface hardness of Nip/H63 were researched. The metallographic structure analysis results proved that the modified copper alloy surface grain was remarkably refined, and the grain refinement degree decreased slightly with increasing rotating speed. EBSD analysis showed that the grain size of Nip/H63 after modification was more concentrated and uniform, particularly between 10 and 25 μm at 500 rpm. Compared with the characteristics of the base metal, the grain size distribution of all modified metals was reduced (2~120 μm). EBSD analysis also showed that the amount of it in each test sample greatly improved after modification for large-angle grain boundaries. The large-angle grain boundaries proportion was 89.2% at 800 rpm, which was much higher than the base material (45.0%). As for hardness and corrosion resistance, FSSP-modified samples were the best at the stirring tool rotation rate of 500 rpm, and the hardness values were 30.1% higher than the base metal. Moreover, these two indicators of the modified layer were improved compared with the base metal under various FSSP parameters. [ABSTRACT FROM AUTHOR]

The "gold dust defect" (GDD) appears at the surface of ferritic stainless steels (FSS) and degrades their appearance. Previous research showed that this defect might be related to intergranular corrosion and that the addition of aluminium improves surface quality. However, the nature and origin of this defect are not properly understood yet. In this study, we performed detailed electron backscatter diffraction analyses and advanced monochromated electron energy-loss spectroscopy experiments combined with machine-learning analyses in order to extract a wealth of information on the GDD. Our results show that the GDD leads to strong textural, chemical, and microstructural heterogeneities. In particular, the surface of affected samples presents an α-fibre texture which is characteristic of poorly recrystallised FSS. It is associated with a specific microstructure in which elongated grains are separated from the matrix by cracks. The edges of the cracks are rich in chromium oxides and MnCr2O4 spinel. In addition, the surface of the affected samples presents a heterogeneous passive layer, in contrast with the surface of unaffected samples, which shows a thicker and continuous passive layer. The quality of the passive layer is improved with the addition of aluminium, explaining the better resistance to the GDD. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) and Y2O3-La2O3 co-stabilized zirconia (La-YSZ) coatings were prepared by atmospheric plasma spraying using identical spray parameters, and their calcium–magnesium–alumina–silicate (CMAS) corrosion behaviors were compared. After CMAS attack, YSZ exhibited a deteriorated microstructure with larger voids and more cracks than La-YSZ. The results revealed that the as-sprayed La-YSZ coatings had a much smaller grain size than YSZ because of La doping but La-YSZ exhibited a better resistance to CMAS than YSZ. Density functional theory calculations showed that the mean square displacement of yttrium in La-YSZ was lower than that of YSZ and the activation energy of CMAS/La-YSZ was higher than that of CMAS/YSZ. EBSD mapping analysis showed La-YSZ coatings have a lower monoclinic/tetragonal ratio than YSZ after corrosion, indicating that the rate of phase transformation in La-YSZ is significantly lower than that in YSZ, which is consistent with calculation results. [ABSTRACT FROM AUTHOR]

Microstructure optimization of Al-Zn-Mg-Cu-Zr aluminum alloys, particularly through recrystallization inhibition, for improved strength and corrosion resistance properties has been an important consideration in alloy development for aerospace applications. Addition of rare earth elements, sometimes combined with Cr, has been found to be beneficial in this regard. In this study, the role of a single addition of 0.1 wt.% Cr on microstructure evolution of an Al-Zn-Mg-Cu-Zr (7449) alloy during processing was systematically investigated by optical light microscopy, scanning electron microscopy, electron backscatter diffraction and scanning transmission electron microscopy. Susceptibility to localized corrosion after aging to T4, T6 and T76 conditions was evaluated by potentiodynamic polarization (PDP) measurements and an intergranular corrosion (IGC) test. A decrease in recrystallized fraction with 0.1 wt.% Cr addition was observed, which is attributed to the formation of Cu- and Zn-containing E (Al18Mg3Cr2) dispersoids and the larger as-cast grain size. Moreover, the depletion of alloying elements from solid solution due to the formation of the Cu- and Zn-containing E (Al18Mg3Cr2) dispersoids and η Mg(Zn,Cu,Al)2 phase at its interface affects grain-boundary precipitation. The observed decrease in localized corrosion susceptibility with minor Cr addition is correlated with the microstructure and equally discussed. [ABSTRACT FROM AUTHOR]

Zn alloys are regarded as one of the most promising alloys for the bioresorbable medical devices due to their outstanding combination of mechanical performance, biodegradability, and biocompatibility. In the present paper, Zn-0.1Mg-1Mn alloy is selected and extruded into tubes at temperatures of 100, 200, and 300 °C in view of its high strength and elongation. The morphology, microstructure, texture, and mechanical properties of the alloy tubes are evaluated. The grains are refined into the sizes of 1.0, 1.5, and 1.9 µm at the extrusion temperature of 100, 200, and 300 °C, respectively. The precipitates arrange along the extrusion direction for the alloy extruded at 100 °C, gradually randomly disperse with the extrusion temperature increasing. The alloy extruded at 100 °C exhibits the excellent properties with the ultimate tensile strength, yield tensile strength, elongation of 405, 380 MPa, and 14%, respectively. The grain refinement and second phase precipitation are responsible for the enhanced strength and the non-basal plane texture contributes the good ductility of the alloy. The fabrication of Zn-0.1Mg-1Mn alloy tube pushes the Zn alloy a further step to produce potentially biodegradable stent. [ABSTRACT FROM AUTHOR]

Recently, researchers have shown interest in developing integrated severe plastic deformation (SPD) processes to produce ultra-fine grained (UFG) metal in a single pass. This article proposes a new integrated severe plastic technique named Multi-angular twist channel extrusion (MATE). The method was devised to impose a large strain in a single pass with better strain homogeneity and lower punch load. The effects of MATE die geometries on the effective strain, strain inhomogeneity, and punch load were analyzed by performing finite element analysis (FEA) to understand the mechanism of the process. The developed artificial neural network (ANN) model was used to optimize the die geometries by genetic algorithm (GA) to attain the desired output characteristics. The twist slope angle (β) = 43°, channel angle (Ø) = 108°, and outer corner angle (ψ) = 50° were determined as the optimum die geometries. With the optimized MATE die, an average effective strain of 2.703 was achieved with good strain homogeneity. Based on the simulation results MATE die was fabricated with the optimum die geometries and experiments were conducted using pure copper. The experimental studies reveal that the ultimate tensile strength and hardness of pure copper was increased by 65.6% and 102%, respectively. The electron back scatter diffraction (EBSD) analysis reveals that the average grain size was 3.1 µm in the extruded copper. The simulated and experimental results corroborate the EBSD findings. [ABSTRACT FROM AUTHOR]

In this study, the microstructural behavior of the advanced Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn-0.15Si (VT8M-1) alloy during rotary swaging (RS) was investigated. VT8M-1 has increased heat resistance and is considered a replacement for the Ti-6Al-4V alloy. It was shown that, during RS, the evolution of the primary a phase is characterized by the formation of predominantly low-angle boundaries according to the mechanism of continuous dynamic recrystallization. The density of low-angle boundaries increases three times: from 0.38 µm−1 to 1.21 µm−1 after RS. The process of spheroidization of the lamellar (a + b) component is incomplete. The average size of globular a and b particles was 0.3 μm (TEM). It is shown that the microstructures after RS (ε = 1.56) and equal-channel angular pressing (ECAP) (ε = 1.4) are significantly different. The temperature–velocity regime and the predominance of shear deformations during ECAP contributed to a noticeable refinement of the primary a-phase and a more complete development of globularization of the lamellar (a+b) component. EBSD studies have shown that RS leads to the formation of a structure with a higher density of low- and high-angle boundaries compared to the structure after ECAP. The results are useful for predicting alloy microstructure in the production of long rods that are further used in forging operations.

This study investigated the microstructure, texture, and mechanical properties of 1050 aluminum alloy sheets that underwent the accumulative roll bonding (ARB) method. The ARB proceeded up to eight passes in three ways: conventional process, preheat between rolling passes (preheating) or anneal between rolling passes (annealing). Heat treatment was done between the ARB passes for 5 min at 150 °C. The mean grain width of the 1050 Al sheet that was 11 μm before ARB, decreased to 295.73 nm, 317.33 nm, or 339.23 nm after six ARB passes in the conventional process, annealed or preheated conditions, respectively. Concurrent heat treatments cause a decrease in the strength of the texture components of Al sheets that were elaborated by the ARB method. Even though conventional and annealed processes successfully enhanced the microhardness by ∼80% and tripled the tensile strength, these improvements were weaker in the preheated condition than the other conditions due to dynamic recovery.

Ultrasonic additive manufacturing (UAM) has garnered significant interest in the aerospace and automotive industries for its structural lightweighting and multi-material joining capabilities. This paper details the investigation on the effect of process variables on the resultant microstructure of the built-up part using UAM for aluminum 6061. The degree of recrystallization is quantified, and an energy metric, defined using the Read–Shockley relationship, is used to build an energy map of the welded part. The total energy stored in the resultant weld interface microstructure is quantified as a fraction of the input and is found to be about 0.1%. The width, average grain size, and percentage of High Angle Grain Boundaries (% HAGB) were used to compare microstructures of builds prepared using different processing conditions. Welding subsequent weld layers was not found to affect the previous welded layers. The effect of vibration amplitude and travel speed on the as-built microstructure were investigated, and the width of the interface was found to more than double when the weld amplitude is increased from the threshold value for joining (23 μm) and then stabilize at higher weld amplitudes. A better understanding of the effect of processing parameters on as-welded microstructures will assist parameter selection for UAM. [ABSTRACT FROM AUTHOR]

The texture and microstructure evolution of aluminum (Al) wire bonds of power semiconductor devices during power cycling tests were investigated using electron backscatter diffraction (EBSD). Power cycling tests in pulse width modulation (PWM) mode were performed on power modules during which the cycled devices were extracted from the test bench at different stages of the aging for analysis. The results improve our understanding of microstructural transition after wire bonding and during power cycling. After the wire was subjected to an ultrasonic bonding process, the evolution of a distinct brass textured area within the bonded interface was observed by EBSD analysis. The brass texture is discussed as a result of plastic deformation. During power cycling, grain coarsening as well as local low angle boundary conversion to high angle boundary occurs and the wire–metallization interface texture changes to an overall random orientation. Effects of microstructure and texture on the crack initiation and propagation are discussed. [ABSTRACT FROM AUTHOR]

With the aim of improving the excellent mechanical properties of the SLM-produced AlSi10Mg alloy, this research focuses on post-processing using ECAP (Equal Channel Angular Pressing). In our article, two different post-processing strategies were investigated: (1) low-temperature annealing (LTA) and subsequent ECAP processing at 150 °C; (2) no heat treatment and subsequent ECAP processing at 350 °C, 400 °C and 450 °C. The microstructure and mechanical properties of this alloy were analyzed at each stage of post-treatment. Metallographic observations, combined with SEM and EBSD studies, showed that the alloys produced by SLM have a unique cellular microstructure consisting of Si networks surrounding the Al-based matrix phase. Low-temperature annealing (LTA), followed by ECAP treatment, facilitated the microstructural evolution of the alloy with partial breakup of the Si network and observed nucleation of β-Si precipitates throughout the Al matrix. This resulted in a Vickers microhardness of 153 HV and a yield strength of 415 MPa. The main results show that post-processing of SLM-produced AlSi10Mg alloys using ECAP significantly affects the microstructural evolution and mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]