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New lamellar Al 2 O 3 /ZrO 2 (Y 2 O 3) eutectics were obtained using seeding melt-grown method. The orientation relationship and interface structure of the eutectics were investigated by means of transmission Kikuchi diffraction and transmission electron microscopy. The unusual orientation relationship of the new Al 2 O 3 /ZrO 2 (Y 2 O 3) eutectics was (1 0 1 2 ¯ )Al 2 O 3 || ( 1 1 ¯ 1)ZrO 2 and [0 2 2 ¯ 1]Al 2 O 3 || [1 1 2]ZrO 2 and the interface plane was (1 0 1 2 ¯ )Al 2 O 3 || ( 1 1 ¯ 1)ZrO 2 with a 4.32% misfit. Furthermore, the possible preferred growth directions on the interface were predicted, which were uncommon low index directions. These results indicate that the interface structure is the leading factor of the growth behavior in binary eutectics. It can be demonstrated that the seeding melt-grown method offers a pathway to tailor the interface and growth direction of the directionally solidified eutectics. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• A β-solidifying TiAl alloy reinforced with ultra-fine yttrium-rich precipitates was consolidated by spark plasma sintering. • This TiAl alloy with refined duplex microstructure exhibited excellent tensile properties at room temperature. • Two types of yttrium-rich precipitates were detected, and the crystallographic relationship between them and γ-TiAl matrix were determined. A β-solidifying TiAl alloy with a refined microstructure and ultra-fine yttrium-rich precipitates that was consolidated by spark plasma sintering was investigated by scanning and transmission electron microscopies. Two categories of yttrium-rich precipitates, Y 2 O 3 and YAl 2 , with sizes ranging from tens to hundreds of nanometers were found to be dispersed within the matrix uniformly. The crystallographic relationship between the two precipitates and the γ-TiAl matrix was determined by the selected area electron diffraction and high-resolution transmission electron microscopy. This spark plasma sintered TiAl alloy was characterized by a uniform duplex microstructure, and it exhibited excellent tensile properties at room temperature. Typically, specimen sintered at 1150°C has an ultimate tensile strength of 1113.1 MPa, yield strength of 881MPa, and a moderate plastic elongation of 1.41%. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Without sacrificing any solution accuracy, an efficient optimization scheme of determining the orientation relationship only based on the daughter phase (i.e., lath martensite in steels in this paper) was established in this work, which involves two key steps. Firstly, an accurate clustering algorithm was developed to perform a statistic of all variants, which can give the most probable orientation and area fraction for each variant. Different from previous methods, the second step is to perform a newly-established optimization scheme, which is able to take variant fractions into consideration to determine the optimal orientation relationship and orientation of prior austenite simultaneously. In this case, the variant-level calculation, which can save much computational time compared with pixel/domain-level calculation, is beneficial for the efficiency promotion. Through inputting the equally-weighted variants into the optimization scheme, the influence of the random cross-sections on the solutions can be effectively eliminated. Furthermore, in-situ high temperature EBSD examinations were first performed to validate solution accuracy, the corresponding results clearly indicated that the orientation of austenite obtained from this approach exhibited a high accuracy and the error is less than 1°.

The microstructure evolution and formation mechanism of the O phase in a Ti-22Al-25Nb (at.%) orthorhombic alloy resulting from different cooling rates were investigated. The results show that the morphology of the precipitated O phase is significantly affected by the cooling rate. As the cooling rate decreases, the floccular O, composed of many fine acicular O phases, gradually grows into the lamellar O phase. When the alloy is cooled from the B2 phase region, the grain boundary O (OGB) preferentially nucleates at the triple junctions and grain boundaries and forms the flat and the zig-zag OGB according to different cooling rates. The OGB consists of separated, flat OGB parts and unconnected, zig-zag OGB composed of multiple short, separated, flat OGB at a higher cooling rate. The zig-zag OGB presents a connected state due to the sufficient diffusion time at a lower cooling rate. When the alloy is cooled from the (B2 + α2) phase region, the increase of the phase boundary provides favorable conditions for the nucleation of the O phase due to the presence of α2 particles. The precipitated rim O phase appears on the periphery of the α2 particles at lower cooling rates. The analysis indicates that the Widmanstätten intragranular O (OWI) precipitated directly from the B2 phase maintains the plane relation with the parent B2 phase, and the Widmanstätten grain boundary O (OWGB) holds the specific orientation relationship with one of the two adjacent B2 grains. The OGB keeps the specific orientation relationship with one of the B2 grains as much as possible. When it cannot maintain the specific orientation relationship with one of the B2 grains, the OGB maintains a near-orientation relationship with B2 grains on both sides to reduce the nucleation activation energy. Moreover, there can be more than one nucleation site for the O phase on a single B2 grain boundary to form the OGB. The rim O phase formed through a decomposition reaction of α2→α2 (Nb-lean) + O (Nb-rich) is controlled by a diffusional mechanism and maintains a specific orientation relationship, i.e., {001} O//{0001} α2 and O//2¯0> α2, with the parent α2 particles.

Determination of strain path across martensitic transformation in materials with two transformation orientation relationships (ORs) is challenging due to the temporal and spatial limitation of the modern techniques. In this work, an analyzing strategy, i.e. , the determination of transformation path via the variant organization feature of martensite, was suggested and applied for the Ni–Mn-based alloys as an example, based on the consideration that the different crystallographic symmetries of transformation systems will result in distinct organizations of martensite variants. For the selected Ni–Mn-based alloys, the orientation examination revealed that both the K−S and the Pitsch OR are respected. Further analyses in terms of the strain and stress compatibility condition and the minimum energy criteria showed that, theoretically, the K−S path produces 2 variants as a self-accommodated variant group, whereas the Pitsch path produces 4 variants as a self-accommodated variant group. Compared with the experimental results, the Pitsch path is the energetically favorable transformation path and actually occurs in stress-free austenite of the Ni−Mn based alloys. The significance of this work is multi-fold. It first resolves the long puzzling issue of transformation strain path of Ni–Mn-based alloys. Moreover, the analyzing scheme can be generalized to determine the transformation characters for martensitic transformation in other systems with multiple possible transformation orientation relationships. Image, graphical abstract [ABSTRACT FROM AUTHOR]

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We developed a fabrication method of thin metal matrix composite films reinforced with ceramic nanoparticles. To this end, we deposited a 20 nm Ni / ultrathin Cr-oxide layer / 20 nm Ni tri-layer on a sapphire substrate, and annealed the sample at the temperature of 700°C. We found that after annealing for 10 min the Cr-oxide layer agglomerates into single- or bi-crystalline faceted Cr 2 O 3 nanoparticles, with the orientation relationship of (11 1 ¯) N i ∥ (0006) C r 2 O 3 and 112 N i ∥ 1 2 ¯ 10 C r 2 O 3 to the Ni matrix. We encountered a surprising vertical spread of the centers of mass of the Cr-oxide particles with respect to the initial position of the Cr-oxide layer. We developed a kinetic model of the evolution of particles shape and of their vertical drift, which enabled an estimate of the effective diffusion coefficient of the Ni-Cr 2 O 3 interface (D i = 7.4 · 10 − 19 m 2 s). Though much slower than grain boundary diffusion in Ni, this interface diffusion enables fast transformation of ultra-thin Cr-oxide layer into an array of isolated Cr 2 O 3 nanoparticles embedded in the Ni film. The insight into the kinetics of the system obtained in the present work paves the way for the design of particle reinforcement of thin metal films with a precise control over the spatial positions of the particles. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Even though it is widely accepted that the Laves phase is a promising strengthener for chromium-containing stainless steels, there is little information available on its microstructural evolution and growth. Therefore, in this study, we analysed the behaviour of Laves (C14) precipitates in high-Cr ferritic stainless steel, Fe-20Cr-2Mo-0.5Nb (at%), annealed at 1073 K for different time periods. A high density of (Fe,Cr) 2 (Mo,Nb) precipitates was formed in the α matrix during annealing. Morphological evolution in the Laves phase followed the sequence of spheroidal → faceted ellipsoidal → faceted needle-like → faceted plate-like. The Laves phase is related to the α matrix by two sets of orientation relationships, viz. OR-1: [ 1 ¯ 1 ¯ 2 ] α / [ 1 2 ¯ 10 ] L , [ 111 ] α / [ 0 1 ¯ 10 ] L , and (1 ¯ 10) α / (000 1 ¯) L and OR-2: [ 1 1 ¯ 0 ] α / [ 0001 ] L , [ 113 ] α / [ 1 ¯ 1 ¯ 20 ] L , and (3 ¯ 3 ¯ 2) α / (1 1 ¯ 00) L. The habit plane of the Laves phase was found to deviate slightly from the (3 ¯ 3 ¯ 2) α / (1 1 ¯ 00) L plane. Interfacial defects, namely disconnections ( b D, h) and super disconnections (m b D , mh), observed experimentally along the habit plane, were consistent with theoretical results based on OR-2 as the reference coordinate frame. The Burgers vector b D exhibited an edge component b y D (0.1539 nm) parallel to Y / [ 113 ] α / [ 1 ¯ 1 ¯ 20 ] L and a small normal component b z D (0.0747 nm) perpendicular to the terraces; meanwhile, the overlap step height h = d (1 1 ¯ 00) L. The morphological evolution of Laves precipitates was described based on the lateral motion of disconnections and super disconnections on { 3 ¯ 3 ¯ 2 } α / { 1 1 ¯ 00 } L terraces in the 〈 113 〉 α / 〈 1 ¯ 1 ¯ 20 〉 direction. Arrays of the disconnections ( b D, h) were found to be capable of accommodating the misfit strain on { 3 ¯ 3 ¯ 2 } α / { 1 1 ¯ 00 } L terraces. Image, graphical abstract [ABSTRACT FROM AUTHOR]

During approximate 773 K aging treatment of 100Mn13 steel, degenerate pearlite will occur and evolve into lamellar pearlite during growth process. The microstructures of degenerate pearlite and its evolutionary lamellar pearlite are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that after 748 K, 773 K and 798 K aging, degenerate pearlites occur at grain boundary. At growth front of degenerate pearlite forming at 773 K and 798 K, pearlite presents a morphology of short lamellae of carbide and ferrite, indicating a trend of developing into lamellar pearlite. The higher the temperature is, the more obvious the trend is, and even a conventional lamellar pearlite has developed. However, there is no morphological evolution for degenerate pearlite forming at 748 K aging. Besides, the constituents of degenerate pearlite is identified as M23C6 and ferrite, and Kurdjumov-Sachs orientation relationship exists between them, (011̅)α//(1.11̅)M23C6, [111]α//[110]M23C6. This orientation relationship maintains in morphological evolution from degenerate pearlite to lamellar pearlite. [ABSTRACT FROM AUTHOR]

It is commonly accepted that prismatic precipitates in Mg alloys are more potent strengtheners than the ones formed on basal planes. However, in most rare-earth (RE) free Mg alloys, precipitation commonly occurs on basal planes. Recent results showed that coupling {10-12} twinning, aging and detwinning (a process termed TAD) promotes prismatic precipitation in Mg-Al alloys by a mechanism that remains unclear. The present work aims to theoretically and experimentally evaluate possible crystallographic orientation relationships (ORs) between the prismatic precipitates and the detwinned matrix in TAD processed samples in order to understand their formation mechanism. A crystallography-based algorithm is proposed to predict such ORs and the predictions are subsequently validated through experimental observation in a transmission electron microscopy (TEM). Three new ORs between Mg 17 Al 12 precipitates and the α-Mg-Al matrix are experimentally determined, which agree well with the predictions of the proposed algorithm after considering the 3.69° rotation of precipitates at twin boundaries. Additionally, the proposed algorithm is validated in other RE free Mg alloys produced via the TAD process, including Mg-Sn-Zn, Mg-Al-Ca, Mg-Zn and Mg-Ca-Zn systems. This work provides a clearer understanding of the ORs between prismatic precipitates and the matrices of Mg alloys that is deemed critical to fully exploit their potential for precipitation hardening. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Herein, the isothermal precipitation behaviors of V(C,N) in ferrite are studied. At 700 °C, the dominant precipitation behavior of V(C,N) is interphase precipitation (IP), whereas at 660 and 620 °C, random precipitation (RP) is dominant. Both IP and RP show the Nishiyama–Wassermann orientation relationship (OR) with ferrite, unlike the common OR between precipitation and ferrite. The size of most precipitated particles varies in the ranges of 5–8 nm at 660 °C and 3–5 nm at 620 °C. The average values of hardness of ferrite grain formed at 700, 660, and 620 °C are 195.1, 237.6, and 278.6 HV, respectively. [ABSTRACT FROM AUTHOR]

The reliability of electronic solder joints is strongly influenced by βSn grain orientations. Single-crystal Cobalt substrates were used to control βSn nucleation and grain orientations in solder joints. On (0001)Co, (11 2 ¯ 0)Co, (10 1 ¯ 0)Co, and (1 1 ¯ 02)Co, interfacial αCoSn 3 crystals that are potent to catalyze βSn nucleation exhibited strong textures with 2–5 symmetric orientations featuring reproducible orientation relationships (ORs) with the Co. Preferred ORs and orientation selections of αCoSn 3 were examined by exploring i) thermodynamic stabilities of interfaces represented by interfacial atomic matches and work of adhesion and interfacial energies calculated based on density functional theory (DFT) and ii) crystal growth kinetics indicated by the angle between (100)CoSn 3 and the substrate plane. In sharp contrast to the innumerable grain orientations in joints on commonly used substrates, dramatically reduced orientations are attributed to the strongly textured αCoSn 3 , on which βSn grains nucleated by fixed ORs. On (11 2 ¯ 0)Co, the total number of orientations including twinned grains were reduced to 20. On (10 1 ¯ 0)Co, none of the βSn orientations exhibit the c-axis perpendicular to the substrate (i.e. parallel to the electron flow direction), which should reduce fast diffusion paths across the joint and improve the reliability of solder joints. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The evolution of microstructure and texture at four strain levels was investigated in Ni–5 at% W alloy by means of electron backscatter diffraction (EBSD) technique. The deformation microstructure evolves gradually from microbands (MBs) to typical lamellar structures with strain increasing in cold-rolled materials, while only lamellar structures in heavily cold-rolled materials. Subsequently, quantitative analysis of microstructure and texture was performed. It indicates that the texture is a typical pure metal deformation texture, but a few cube and rolling direction (RD)-rotated cube orientations also can be observed in the deformed samples. The use of high-temperature annealing enables an area fraction of cube orientation > 95% to be obtained for high strained substrate. In addition, it is worth noting that the point-to-point misorientation inside the band with various orientations is found to keep quite low. But the point-to-origin misorientation over the same distance is dependent on strain and orientation type in the band. The cube-oriented regions were characterized by a high accumulated orientation gradient, close to 28°, compared to the non-cube-oriented regions. This means that the accumulated orientation gradient only occurs in the cube band with the reduction of 98%, which partly explains the formation of strong cube texture after high-temperature annealing. [ABSTRACT FROM AUTHOR]

The well-known problem of determining the maximum possible disorientation angle of two cubes is extended to groups of three to six cubes. This problem is considered here to allow identification of specific arrangements of grains with a cubic structure at triple-line or quadruple junctions in polycrystals. The minimum disorientation angle between cubes in the group is defined as the characteristic disorientation angle θ c d of the group. The maximum values of θ c d and the arrangements of cubes giving the maximum θ c d are determined for groups of three to six cubes. [ABSTRACT FROM AUTHOR]

In this manuscript, we attempt to clarify the capability of utilisation of α-FeSi2 nanocrystals as a buffer layer for growth of monocrystalline/high-quality β-FeSi2 direct-gap semiconductor from the point of view of the crystal lattice misfits and near coincidence site (NCS) lattices. Iron silicides-based nanostructures have a wide spectrum of possible industrial applications in different fields. Mainly, interest in these functional materials is caused by their ecological safety and Earth's core abundance that give us the opportunity for greener future with highly effective electronic devices. β-FeSi2 phase due to its allowed direct transition with energy close to 0.87 eV can be used as active material in light emission diodes (LED). Utilisation of buffer layers between silicon substrate and give one more tool to engineer the band structure of semiconducting β‑FeSi2 phase. We attempt to clarify the capability of the utilisation of the α-FeSi2 phase as a buffer layer for the growth of β-FeSi2 direct-gap semiconductor from the point of view of the crystal lattice misfits and near coincidence site (NCS) lattices. Possible β-FeSi2/α-,γ-,s-FeSi2/Si orientation relationships (ORs) and habit planes were examined with crystallogeometrical approaches and compared with β-FeSi2/Si ones. The lowest interplanar and interatomic spacing misfits between silicon lattice and a silicide one are observed for the pair of s-FeSi2{011}[200]/Si{022}[100] at room temperature and equal to –0.57%. The least interplanar and interatomic spacing misfit of 1.7 and 1.88%, respectively, for β-FeSi2/Si, can be decreased as low as –0.67 (interplanar) and 0.87 (interatomic) % by placing an α-FeSi2 layer between silicon and β-FeSi2 phase. It is stated that the growth of metastable γ-FeSi2 is also favourable on silicon due to low interplanar and interatomic spacing misfit (–0.77%) and a higher density of NCS in comparison with s-FeSi2. Design and technological procedure for the synthesis of possible β-FeSi2/α-FeSi2/Si heterostructure have been proposed based on the results obtained. [ABSTRACT FROM AUTHOR]

The orientation relationships between the coating and the substrate after galvanizing (GI) and galvannealing (GA) have been studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The δ phases in the coatings predominantly have { 11 2 ¯ 0 } , { 10 1 ¯ 0 } and { 10 1 ¯ 3 } plane textures and showing the semi-coherent relationship with the {111} plane of the substrate. It has been found that these types of texture components are essential for the bond between the coating and the substrate. The percentage of { 11 2 ¯ 0 } , { 10 1 ¯ 0 } and { 10 1 ¯ 3 } texture components increases initially with the increase of the holding time during the GA process before decreasing. [ABSTRACT FROM AUTHOR]

A pure crystallogeometrical approach is proposed for predicting orientation relationships, habit planes and atomic structures of the interfaces between phases, which is applicable to systems of low‐symmetry phases and epitaxial thin film growth. The suggested models are verified with the example of epitaxial growth of α‐, γ‐ and β‐FeSi2 silicide thin films on silicon substrates. The density of near‐coincidence sites is shown to have a decisive role in the determination of epitaxial thin film orientation and explains the superior quality of β‐FeSi2 thin grown on Si(111) over Si(001) substrates despite larger lattice misfits. Ideal conjunctions for interfaces between the silicide phases are predicted and this allows for utilization of a thin buffer α‐FeSi2 layer for oriented growth of β‐FeSi2 nanostructures on Si(001). The thermal expansion coefficients are obtained within quasi‐harmonic approximation from the DFT calculations to study the influence of temperature on the lattice strains in the derived interfaces. Faster decrease of misfits at the α‐FeSi2(001)||Si(001) interface compared to γ‐FeSi2(001)||Si(001) elucidates the origins of temperature‐driven change of the phase growing on silicon substrates. The proposed approach guides from bulk phase unit cells to the construction of the interface atomic structures and appears to be a powerful tool for the prediction of interfaces between arbitrary phases for subsequent theoretical investigation and epitaxial film synthesis. [ABSTRACT FROM AUTHOR]

The oxidation kinetics of interstitial free (IF) steel were shown to differ remarkably, by more than one order of magnitude, with the crystallographic texture of the metallic substrate. More specifically, γ-fiber or ND||<111> grains oxidized preferentially and provided epitaxial or pseudo-epitaxial growth of the corresponding oxide grains. Below 843K, the initial magnetite (Fe 3 O 4) grains had a ∼45°<001> epitaxial orientation relationship with all the substrate ferrite grains. Specimens oxidized at temperature > 843K, on the other hand, had a pseudo-epitaxy: ND||<111> metallic-substrate grains generated ND||<001> pro-eutectoid magnetite. In both cases, the oxide grains growing from ND||<111> ferrite had more dislocations and higher tensile residual stresses. They also had more magnetite and less hematite. It was proposed that the oxide phase growing from ND||<111> ferrite grains, with higher dislocation content, has faster ionic diffusion. Faster diffusion in the magnetite also appeared to reduce the protective (lower ionic diffusion) outer hematite layer. A combination of these two generated thicker oxide layers on the ND||<111> ferrite grains. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We propose a new electron backscatter diffraction (EBSD) indexing approach that can handle overlapping patterns arising from fine-scale mixtures of two crystallographically distinct but related phases. The approach relies on a combination of spherical indexing (SI) with an overlap master pattern (OMP) in which the two phases have the proper orientation relation. We illustrate the approach using a Ti-10-2-3 sample and compare results from traditional Hough-based indexing of the α and β -phases with SI maps. We show that the SI approach produces superior orientation maps, and we present a symmetry-based algorithm for the determination of the α -phase variant when experimental patterns are indexed with respect to the OMP. We illustrate the use of the OMP to determine the parent β -phase volume fraction and obtain excellent agreement with Thermo-Calc phase fraction predictions. [ABSTRACT FROM AUTHOR]

The paper describes the microstructure evolution by high-temperature compression of a high Nb-containing TiAl alloy. The paper extends a previous publication [Song, et al. Intermetallics 109 (2019) 91–96], in which a unique twin-like morphology in the α 2 (Ti 3 Al) phase was reported. However, the origin of these structures could not be clarified without doubt. The present study is focused on phase transformations that in this multiphase alloy can be associated with deformation. Particular attention is paid to local transformations of the α 2 phase into O phase or ω-related phases, which, because of structural and chemical similarity of these phases with α 2 , can easily occur and could mistakenly be considered as a twin structure. The details of the atomic processes involved are elucidated by electron microscopy. Given the large shufflings and the atomic site interchanges required for the operation of this twinning system, it is concluded that twinning of the α 2 phase is a diffusive-displacive process. Within the α 2 phase, ω o is heterogeneously nucleated. The nucleation sites are defect-rich areas, which are subjected to high local stresses. The study strongly emphasizes the close relationship between high-temperature deformation and phase transformations in multiphase titanium aluminide alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Thermo-mechanical treatment is an effective way to tune the microstructure and enhance the output strain of NiMn-based magnetic shape memory alloys through field driven variant reorientation or structural transformation. Comprehensive knowledge on the microstructural feature and related transformation crystallography is of great importance for the microstructure control and property optimization. In this work, we demonstrate the crossing twin of seven-layered modulated (7 M) martensite assembled in herringbone shape induced by thermo-mechanical treatment in a directionally solidified Ni 50 Mn 30 Ga 20 alloy. Based on the electron backscatter diffraction (EBSD) measurements, it is found that the crossing twin is composed of four 7 M martensite variants with two mutually crossing systems of twin, i.e. , type I twin and compound twin. The type I twin in the crossing twin, being with {1 –2 10} 7 M as the twinning plane, is quite different from that of the self-accommodated martensite (i.e. , {1 –2 –10} 7 M as the twinning plane). A novel transformation orientation relationship between austenite and 7 M martensite in crossing twin is resolved to be {1 0 1} A //{1 –2 10} 7 M and <1 0 –1> A //<10 10 1> 7 M , in contrast to that of self-accommodated case, i.e. , {1 0 1} A //{1 –2 –10} 7 M and <1 0 –1> A //<–10 –10 1> 7 M. By using the experimentally determined orientation relationship between two phases to construct the deformation gradient matrix, the underlying mechanism for the selection of twinning system is further discussed. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The understanding on the interfaces between different polymorphs of nanosized TiO2 from the perspective of crystallography has great theoretical value for the interface and property design and regulation. In this work, TiO2 (B)/anatase dual‐phase nanofibers containing different interface structures are investigated in detail. The X‐ray diffraction (XRD) is first employed to illustrate the detailed phase evolution during the calcination under different temperatures. Four types of interfaces with different structures are further studied by transmission electron microscopy (TEM). Single crystal form induced different interfaces is confirmed, which is thought to be the universal conclusion in monoclinic crystal systems. Meanwhile, the other two interface structures in {100} single crystal form are also observed in the samples under higher temperature calcination. Invariant line strain calculation is carried out for the four interfaces. The calculated crystallographic features agree well with the observed results. Furthermore, taken [010]TB//[001]TA as the rotation axis, the orientation difference of the single crystal form induced interfaces is confirmed to be 72.5°, corresponding to the β angle of TiO2 (B). The orientation relationships of the other two interfaces in {100} single crystal form can also be achieved by 7.5° and −4.5° rotation from the interface with the same single crystal form. [ABSTRACT FROM AUTHOR]

An austenitic B2-CuZr phase, when deformed, can undergo a martensitic transformation (MT) that produces a martensitic B19′-CuZr phase, resulting in remarkable transformation-induced plasticity (TRIP) and shape memory effects in B2-structured alloys. However, the shear mechanism as well as the crystallographic characteristics, which underlie the MT and, in turn, the TRIP and shape memory effects, remain unclear and somewhat controversial. Here we report that a single shear on {110} B2 <001> B2 , along with {1 1 5.5} B2 being the habit plane, are responsible for the MT in B2-CuZr, where {110} B2 and <001> B2 are the shear plane and the shear direction, respectively. These were revealed by determining unambiguously the orientation relationship between B2 and B19′, co-existing in individual spherulites contained in a B2-CuZr-containing bulk metal glass-matrix composite (BMGC). This exotic microstructure, featuring a core-shell like distribution in each single spherulite in which all the 12 possible martensite (B19′) variants constitute the core and the parent B2 forms the shell, was made from an incomplete MT in originally mono-crystalline B2 spherulites of the as-cast BMGC when subjected to moderately applied frictional shear stresses upon mechanical grinding. Finite element analysis suggests that a core-shell like shear stress distribution inside a B2 spherulite, caused by the confinement of the stiffer glass matrix, may account for it. These results provide direct experimental evidence to elucidate the B2→B19′ MT and its variant selections under various stress states, and pave the way for developing ductile B2-structured alloys, including but not limited to, shape memory intermetallics, high entropy alloys and B2-containing composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The evolution of the deformation-induced martensite in the drawn 316L stainless steel and its effect on mechanical performance are examined. Both the yield strength and ultimate tensile strength of the 316L wire reach over 2.3 GPa at a drawing strain of 3.44. The deformation production of the wire during the drawing process is dislocation, twin and finally, deformation-induced α′-martensite. The neighboring misorientation between α′-martensite shows a preferential distribution around 60° due to variant selection limited by a double K–S orientation relationship. This preferential misorientation distribution around ∼60° is stable during the drawing process, and the α′-martensite has been refined to possess an average boundary spacing of ∼50 nm at a strain of 3.44. • The strength of the 316L reached 2340 MPa through cold drawing. • 316L with nanoscale lamellar structures of γ (52 nm) and α′ (53 nm) were prepared. • Misorientation between α′-martensite shows a preferential distribution around 60°. [ABSTRACT FROM AUTHOR]

The microstructural evolution and strengthening behavior of a polycrystalline Ni 3 Al-based intermetallic alloy were investigated during varying durations of thermal exposure at 1100 °C. The study focused on the topologically closed-packed orthorhombic P phase precipitate, which was found to form in the interdendritic γ channel and grow in the γ' -matrix after thermal exposure. The morphology of the P phase evolved from needle-like to lath-like and then to blocky-like. The crystal structure and composition of the precipitates were analyzed using scanning transmission electron microscopy (STEM) and electron probe X-ray microanalysis (EPMA). The chemical composition of the P phase changed continuously during thermal exposure and the P phase was related to the γ' -matrix by three sets of orientation relationships (OR). The alloy's tensile properties and creep fracture time were enhanced during thermal exposure at 1100 °C for 2000 h due to P phase precipitation at grain boundaries or within the grain. Based on the experimental evidence of this study and theoretical strengthening behavior reported in the literature, a novel mechanism for in-situ precipitation strengthening was proposed. [Display omitted] [ABSTRACT FROM AUTHOR]

The microstructure evolution and mechanical properties of quaternary Al-Cu-Si-Mg eutectic alloy prepared via arc melting and suction casting were studied. This alloy exhibits a single endothermic DSC peak with a melting temperature of 509 °C upon heating, suggesting a eutectic reaction. The cast alloy microstructure consisted of four phases, α-Al, Al2Cu (θ), Si and Al4Cu2Mg8Si7 (Q), in the eutectic cells and also in the nano-scale anomalous eutectic in the intercellular regions. The eutectic cells show different morphologies in different parts of the sample. Well-defined orientation relationships between the α-Al, Al2Cu, and Q phases were found in the eutectic cell centres, while decoupled growth of Q phase occurred at the cell boundaries. The bimodal microstructure exhibits excellent compressive mechanical properties, including a yield strength of 835 ± 35 MPa, a fracture strength of ~1 GPa and a compressive fracture strain of 4.7 ± 1.1%. The high strength is attributed to a combination of a refined eutectic structure and strengthening from multiple hard phases.

The mechanical and magnetic properties of Ni–Mn–Sb intermetallic compounds are closely related to the martensitic transformation and martensite variant organization. However, studies of these issues are very limited. Thus, a thorough crystallographic investigation of the martensitic transformation orientation relationship (OR), the transformation deformation and their impact on the variant organization of an Ni50Mn38Sb12 alloy using scanning electron microscopy/electron backscatter diffraction (SEM/EBSD) was conducted in this work. It is shown that the martensite variants are hierarchically organized into plates, each possessing four distinct twin-related variants, and the plates into plate colonies, each containing four distinct plates delimited by compatible and incompatible plate interfaces. Such a characteristic organization is produced by the martensitic transformation. It is revealed that the transformation obeys the Pitsch relation ({0{\overline 1}{\overline 1}}A // {2{\overline 2}{\overline 1}}M and 〈0{\overline 1}1〉A // 〈{\overline 1}{\overline 2}2〉M; the subscripts A and M refer to austenite and martensite, respectively). The type I twinning plane K1 of the intra-plate variants and the compatible plate interface plane correspond to the respective orientation relationship planes {0{\overline 1}{\overline 1}}A and {0{\overline 1}{\overline 1}}A of austenite. The three {0{\overline 1}{\overline 1}}A planes possessed by each pair of compatible plates, one corresponding to the compatible plate interface and the other two to the variants in the two plates, are interrelated by 60° and belong to a single 〈11{\overline 1}〉A axis zone. The {0{\overline 1}{\overline 1}}A planes representing the two pairs of compatible plates in each plate colony belong to two 〈11{\overline 1}〉A axis zones having one {0{\overline 1}{\overline 1}}A plane in common. This common plane defines the compatible plate interfaces of the two pairs of plates. The transformation strains to form the variants in the compatible plates are compatible and demonstrate an edge-to-edge character. Thus, such plates should nucleate and grow simultaneously. On the other hand, the strains to form the variants in the incompatible plates are incompatible, so they nucleate and grow separately until they meet during the transformation. The results of the present work provide comprehensive information on the martensitic transformation of Ni–Mn–Sb intermetallic compounds and its impact on martensite variant organization.

Influence of 1.5 wt% Nd addition on microstructures and mechanical properties of the as-extruded Mg−6.0Zn–0.5Zr (ZK60) alloy was studied. The results illustrate that Nd addition clearly refines dynamic recrystallized grains but has almost no influence on texture. Additionally, the intermetallic phases were significantly altered by Nd addition. In ZK60 alloy, the coarse intermetallic phases are MgZn 2 , Mg 21 Zn 25 , Mg 4 Zn 7 , MgZn and I-phase, while MgNdZn 3 (W), Mg 43 Zn 51 Nd 6 (T), MgZn 2 and Nd-enriched MgZn after Nd addition. Also, three kinds of new orientation relationships (ORs) between MgZn 2 or its twin domain and Mg were revealed in this work while both MgZn 2 and W were found to be coherent with T following identical ORs. Furthermore, the fine precipitates are with sizes of ∼20 nm and were confirmed as MgZn 2 , MgZn 2 + MgZn and Mg 4 Zn 7 + MgZn 2 in ZK60 alloy while new spherical Guinier Preston (G.P.) zones with sizes of ∼5 nm after Nd addition. Finally, the above microstructural modifications because of Nd addition result in ultra-high strength for ZK60 alloy, with tensile yield strength being approximately 408 MPa. Image 1 • Nd addition clearly refines DRX grains while with almost no effect on texture. • MgZn 2 , Mg 21 Zn 25 , Mg 4 Zn 7 , MgZn and I-phase were revealed in the ZK60 alloy. • W, Mg 43 Zn 51 Nd 6 (T), MgZn 2 , Nd-enriched MgZn and G.P. zones formed after Nd addition. • Three kinds of new ORs between MgZn 2 or its twin domain and Mg were revealed. • The ZK60 + 1.5Nd alloy exhibits high tensile yield strength of approximately 408 MPa. [ABSTRACT FROM AUTHOR]

• Propose a geometrical model to predict the preferred orientation relationship. • Propose a three-dimensional space to characterize an orientation relationship. • The predicted Orientation relationships are consistent with most experimental observations in publication. A geometrical model is proposed to predict the preferred orientation relationship (OR) between two crystals. While the rotating crystal is rotated with respect to the fixed crystal, a crystallographic OR emerges as long as some intersected reciprocal lattice points (RLPs) lie in a plane and form a periodic pattern. The preferred ORs can be determined when the coplanar RLPs of both crystals reach maximum on the plane determined by the intersected RLPs. Calculations were carried out on TiB/α-Ti, TiB/β-Ti and α-Ti/β-Ti systems, and the predicted preferential ORs are consistent with most experimental observations in publication, showing the validity of the model on the prediction of preferred OR between BCC, orthorhombic and HCP crystals. Moreover, a full OR space with a right cylinder shape is introduced to characterize an OR between two crystals. The basal plane of the cylinder reflects the symmetry of the fixed crystal and the vertical height of the cylinder represents the symmetry of an indicator axis of the rotating crystal. According to the symmetry of both crystals, the full OR space can be divided into several equivalent subspaces. This unique geometrical OR presentation effectively eliminates the ambiguities in conventional Miller indices OR presentation and enable a visual and convenient comparison of ORs from different research sources. [ABSTRACT FROM AUTHOR]

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In this work, two types of stress induced hexagonal close packed structure to face centered cubic structure transformation were observed in cold-rolled pure titanium. The corresponding transformation mechanisms were revealed by high resolution transmission electron microscopy. By using stereographic projections and selected area electron diffraction simulations, the three dimensional orientation relationships for the two types of phase transformation were deduced for the first time. The deduced orientation relationships were also verified by high resolution transmission electron microscopy observations, and the dark side of the basal-type face centered cubic phase was revealed at the atomic scale. Unlabelled Image • Two types of hcp to fcc transformations were characterized at atomic scale by HRTEM. • 3-D orientation relationships for hcp to fcc transformation were investigated in Ti. • The deduced 3-D orientation relationships were verified by HRTEM observations. • A guidance for studying the 3-D morphology of fcc phase in hcp phase was provided. [ABSTRACT FROM AUTHOR]

Electron Backscattering Diffraction (EBSD) is a well-known technique which is primarily used to analyse the microstructural features in metallic materials, including the orientation relationship between microstructural constituents. However, its versatility has not yet been critically utilized to establish crystallographic relationships involved in phase transformation of ceramics. In view of the significance of transformation twinning in ceramics on mechanical properties, the representative orientation relationships in twinned grains of CaTiO 3 is investigated using EBSD. It is observed that the matrix/twin pairs of CaTiO 3 have misorientation angles at 87°, 90° and 98°. The misorientations associated with the boundaries between twin/twin pairs formed by different twinning orientation relationships are noted at 90°, 91°, 92° and 98°. On the basis of the orientation relationships, the crystallography of cubic to orthorhombic and tetragonal to orthorhombic phase transformations in CaTiO 3 is explored. The most favorable orientation relationships pertaining to such a phase transformation are (001) o [ 100 ] o || (03 1 ¯ ) c [ 3 ¯ 13 ] c between parent cubic and daughter orthorhombic phases and (001) o [ 100 ] o || (1 1 ¯ 2 ¯ ) t [ 8 ¯ 2 ¯ 3 ¯ ] t between parent tetragonal and daughter orthorhombic phases of CaTiO 3. [ABSTRACT FROM AUTHOR]

In this paper, strains are monitored in-situ at the surface of a polycrystalline 316 L sample loaded quasi-statically in uniaxial tension. Initial orientation data collected over thousands of grains is compared with the strain data evolution in order to investigate, with statistical significance, the relationship between the microstructural features and the strain localization patterns emerging at the grain scale. It is shown quantitatively that high values of strain appear early and primarily around grain boundaries, before growing into a network spanning several grains and grain boundaries. Strains are also heterogeneous within a grain, with the heterogeneity tending to be more pronounced in larger grains. Statistical analyses demonstrate that the usual microstructural descriptors—such as Taylor factors, average intragranular misorientation angles or intergranular misorientation angles—do not display any correlation with the localization network. Furthermore, higher Schmid factors, albeit exhibiting some weak correlation with higher strains, fail to systematically identify the grains that experience the largest strains. It is thus proposed to analyze three-dimensional descriptors of orientation expressed in the Rodrigues space and they are shown to help readily identify orientations that exhibit high strains early in the loading. Additionally, the study of the full three-dimensional misorientation information, expressed in the reduced Rodrigues space, clearly highlights the fact that some misorientations oppose localization at certain boundaries in the microstructure at hand. Hence, considering the full three-dimensional orientation (and misorientation) data instead of just scalar descriptors is demonstrated to be of great interest when investigating the relationship between microstructural features and strain localization. [ABSTRACT FROM AUTHOR]

Crystallographic orientation relationships (ORs) among α-Fe, cementite θ-Fe 3 C 1-z , and hexagonal close-packed iron carbide/(carbo)nitride ε-Fe 3 (N,C) 1+x are highly important to phase transformations and microstructure evolution during heat-treating of cast irons and steels, and during nitriding of these materials. Several α/θ, ε/θ, and α/ε two-phase ORs have been controversially discussed in literature. In that regard, an α/ε/θ three-phase crystallographic relation has been hypothesized, yet hitherto hardly verified, which justifies the existence of two distinct α/θ ORs by making use of an ε intermediate in the θ formation. In this study, ORs in a white-solidified and gas-nitrided hypoeutectic Fe-3.5 wt%C-1.5 wt%Si model alloy were investigated by electron backscatter diffraction (EBSD). The specific alloy composition and nitriding conditions allow simultaneously examining α/θ, ε/θ and α/ε ORs, and particularly the α/ε/θ three-phase relationship, which can be hardly assessed simultaneously in conventionally treated cast irons and steels. Eutectic cementite and pearlite constitute the white-solidified microstructure. Eutectic cementite and pearlitic α-Fe frequently fulfill the Isaichev OR and certain ORs, which are close to the Pitsch-Petch OR. Upon nitriding, ε forms from surface-adjacent cementite, whereas α has largely been retained due to the presence of Si. About 70% of the ε grains fulfill the OR 010 θ ∥ 11 2 ¯ 2 ¯ ε / 100 θ ∥ 11 2 ¯ 3 ε. The orientation of α adjacent to the newly formed ε determines which variant of that ε/θ OR is selected. Thereby, irrespective of the two main α/θ ORs, basically the same α/ε OR is established. The α-affected variant selection proves the existence of an α/ε/θ three-phase crystallographic relationship given by 03 1 ¯ θ ∥ 10 1 ¯ 1 ¯ ε ∥ 10 1 ¯ α / 100 θ ∥ 11 2 ¯ 3 ε ∥ 131 α or 1 ¯ 1 1 ¯ α. Image 1 [ABSTRACT FROM AUTHOR]

The present investigation aims at studying the effect of different welding techniques on the microstructure and mechanical properties of the welds. Weld zone (WZ) in the metal inert gas (MIG) welding, contains higher martensite fraction compared to arc and tungsten inert gas (TIG) welding. The micro-hardness of the WZ was found to be maximum after MIG welding (220 ± 14 HV) in comparison to arc welding (190 ± 12 HV), TIG welding (142 ± 10 HV) and friction stir welding (FSW) (202 ± 10 HV) as well as the base metal (BM) (108 ± 14 HV). The joints fabricated via MIG welding exhibited higher tensile strength (371 ± 10 MPa) as compared to other welding techniques (arc and FSW). The ductility of the parent metal was 42 ± 2% whereas the ductility of the MIG and arc joints were lower (13 ± 2% and 17 ± 3% respectively) due to the presence of martensite during fusion welding. The FSW joint shows higher yield and tensile strengths (356 ± 8 MPa) along with higher elongation (22 ± 4%) compared to fusion-welded joints due to the presence of fine, equiaxed recrystallized grains in the WZ. Fracture occurs at the HAZ/base metal interface, where the hardness is lower compared to the WZ. Compressive and tensile residual stress is obtained in the WZ upon fusion and FSW, respectively. In this paper, analytical tools are used to calculate the orientation of prior austenite (γ) in the MIG weld joint. The texture of high temperature γ phase is simulated for the different welding techniques. The occurrence of the Kurdjumov–Sachs (K S) orientation relationship (OR) is determined from the martensite grains in MIG weld. The texture investigation showed the occurrence of texture memory effect of ferrite in the HAZ after MIG welding. [ABSTRACT FROM AUTHOR]

Abstract A systematic variation in the orientation relationship (OR) of Ag films grown on Ni substrates previously discovered by a combinatorial approach is analyzed using concepts of grain boundaries, surface science and phase transformations. On roughly half of all Ni substrate orientations, Ag adopts a "special" OR that varies systematically from a twin OR, which develops on substrates lying along the (111)–(210) line of the standard stereographic triangle (SST), to the so-called oct-cube OR, which arises exclusively on (100) substrates. On the other half of Ni substrate orientations, Ag adopts the standard cube-on-cube OR. The special ORs are modeled by a) linear interpolation, b) 1D edge-to-edge matching and c) 2D transformation strains, using the twin relationship as a reference. The 1D model shows that the systematic variation in the special ORs can be understood in terms of a growth mechanism by attachment at steps and a lattice rotation due to the difference between the step heights in the substrate and the film. The 2D model explains why this mechanism does not apply to substrates on which Ag displays the cube-on-cube OR. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Here we report a new crystallographic orientation relationship (OR) between MC-type carbide (M = metal) and ferrite matrix, observed in the specimen held isothermally at 600 °C for 20 min, named NEU-OR. The 〈110〉 carbide //〈110〉 ferrite alignment is the main difference from the well-known Baker–Nutting (BN) OR. NEU-OR is related to BN OR by the relative rotation of 45° about the zone axis of 〈110〉 carbide. The interfacial energy between carbide and ferrite with NEU-OR is lower than that with BN OR based on semi-coherent dislocation theory, which benefits increases in the number density of precipitates. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract A computer program was employed to reconstruct the parent microstructure from electron backscatter diffraction maps taken from martensite. The reconstruction is based on a given user-selected orientation relationship. Two reduced-activation ferritic-martensitic Eurofer steels were austenitized for several times and cooled down at different rates. Two parameters are proposed to assess the quality of the reconstruction: the relative frequency of orientations in a determined sub-portion of the Euler space and the distribution of the angular deviation from a given theoretical orientation relationship. The number of active martensitic orientation variants during the transformation depends on grain size. Coarser grains enable a greater number of active variants improving the reconstruction quality. The distributions of angular deviations reveal that the Greninger-Troiano orientation relationship is the one that best describes the martensitic transformation in both steel grades. Highlights • Reconstruction of parent grain structure in Eurofer-type steels using EBSD. • Two parameters are proposed to assess the quality of the reconstructions. • The quality of the reconstructions depends on grain size. • Greninger-Troiano OR best describes their martensitic transformation. [ABSTRACT FROM AUTHOR]

Abstract Zirconium carbide (ZrC x) is an important structural material. Its high strength and hardness makes it suitable for application in hard materials and non-oxide type new ceramics. Hence, several researches have been carried out with the aim of understanding its mechanical properties. In this paper, the mechanical properties of ZrC x (0.45 ≤ x ≤ 0.72) were investigated considering the grain size effect. The bending strength as a function of grain size obeyed the Hall–Petch relation. The composition dependence of the strength linearly decreased with decreasing carbon content, followed by saturation at x = 0.6, corresponding to the lowest x value of the ZrC x single phase region. The Young's modulus and hardness monotonically decreased with decreasing carbon content, independently of grain size. The annealing of ZrC 0.45 at 1273 K for 18 ks led to the formation of Zr precipitates, which showed an orientation relationship with the ZrC matrix of (0001) Zr //(111) ZrC. These precipitations formed compressive residual stress in the ZrC phase, resulting in an 80% increase in the bending strength after annealing. Graphical abstract fx1 Highlights • Effect of composition and grain size on mechanical properties of ZrC x investigated. • Bending strength obeyed the Hall–Petch relation. • Young's modulus and hardness were independent of grain size. • Young's modulus and hardness monotonically decreased with decreasing carbon content. • Annealing of ZrC 0.45 formed coherent Zr precipitates, improving bending strength. [ABSTRACT FROM AUTHOR]

Abstract Generally, the formation of Laves phase precipitates is induced by heat treatment, and deformation-induced precipitation of these phases has not been reported so far. In this work, we observed the precipitation of the compression-induced C14 laves phase particles along dislocation walls within B2 TiFe phase in a semi-solid sintered TiFeCo alloy. Interestingly, coherent interfaces were formed between the Laves phase and the TiFe parent phase, and the corresponding orientation relationships: (01 1 ¯ 1) C 14 // (1 ¯ 10) B 2 and [ 2 1 ¯ 1 ¯ 0 ] C 14 // [ 001 ] B 2 . The present study indicates that the feasibility that Laves phases can be introduced into metallic materials by deformation processing. Highlights • We firstly find that Laves phases can be induced by deformation processing. • Coherent interfaces were formed between Laves precipitates and parent phases. • The orientation relationships agree with theoretical prediction of Rong–Dunlop. • The induced precipitates can obviously improve mechanical properties of the alloy. • Our results provide a novel route for fabricating high-strength metallic alloys. [ABSTRACT FROM AUTHOR]