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The epitaxial alignment of Mn2GaC MAX phase on 12 common single‐crystalline substrates is analyzed through a crystallographical approach utilizing near‐coincidence site lattices. This method effectively predicts epitaxial relationships in MAX phase thin films grown on MgO$$ \text{MgO} $$(111) and Al2O3$\left(\text{Al}\right)_{2} \left(\text{O}\right)_{3}$(001), as well as prospective rutile, muscovite, MgAl2O4$\left(\text{MgAl}\right)_{2} \left(\text{O}\right)_{4}$ and SrTiO3$\left(\text{SrTiO}\right)_{3}$ substrates, highlighting the chemical affinities and atomic configurations at their interfaces. Novel epitaxial relationships for Mn2GaC MAX phase are identified, offering alternatives to the traditional (001) out‐of‐plane orientation and exploring variations in epitaxial lattice stress. Additionally, this study examines the temperature dependence of interface strain for the most promising orientation relationship candidates, offering insights into the effect of substrate temperature on the growth of the MAX phase thin films. [ABSTRACT FROM AUTHOR]

The 12% Cr heat-resistant steel used for critical components of fossil-fired power plants works in high-temperature and high-pressure steam environments for a long time and inevitably undergoes a certain amount of plastic deformation during service. This plastic deformation will affect the microstructure and hot ductility of the heat-resistant steel and ultimately influence its service life. Therefore, the effect of hot compression deformation on microstructural evolution at 650°C was investigated in this work. As the amount of hot compression deformation increased, the number of subgrains significantly increased, and their sizes gradually decreased. When the amount of deformation reached 50%, dynamic recrystallization occurred, forming a preferred orientation in the rolling direction. <111> and <001> fiber texture appeared in the microstructure when the deformation amount reached 8%, and the intensity of <111> texture was significantly higher than that of <001> texture. Their intensity values further increased with the increase of the amount of deformation. As the amount of hot compression deformation increased, the deviation angle of the Kurdjumov–Sachs (KS) orientation relationship between M23C6 particles and α-Fe gradually increased. Their KS orientation relationship began to be disrupted at the deformation amount of 6% and was completely destroyed at the deformation amount of 20%. With the amount of deformation increasing up to 50%, there were no micropores at the M23C6/matrix interfaces, and no hot cracking occurred. This was mainly attributed to the occurrence of dynamic recrystallization which alleviated stress concentration at the particles /matrix interfaces. The mechanisms of microstructural evolution involving subgrains, grain boundary characteristics, texture evolution, strain distribution, and orientation relationship were discussed in detail. [ABSTRACT FROM AUTHOR]

Nano Al3Ti‐TiB2‐AlN‐TiN/Al inoculant ribbons containing a large number of evenly distributed nanoparticles, such as Al3Ti (sized about 300 nm), TiB2 (sized about 100 nm), AlN (sized about 150 nm), and TiN (sized about 200 nm), were prepared by vacuum rapid quenching furnace to refine AlZnMgCu alloys. The nano Al3Ti‐TiB2‐AlN‐TiN/Al inoculant ribbons showed an excellent inoculant effect, which modified the dendrite crystals to equiaxed crystals and refined the grains from 122 ± 4 µm to 36 ± 5 µm by the addition of 0.3 wt% nano Al3Ti‐TiB2‐AlN‐TiN/Al inoculant ribbons. In addition to nano Al3Ti and TiB2 particles, nano AlN and TiN particles also have a certain orientation relationship with α‐Al, which suggests that these particles possess nucleation potency to α‐Al. After inoculation with 0.3% nano Al3Ti‐TiB2‐AlN‐TiN/Al inoculant ribbons, the ultimate tensile strength, yield strength, and average microhardness of the AlZnMgCu alloys increased from 246 MPa, 79 MPa, and 112 HV to 319 MPa, 100 MPa, and 136 HV, or by 29.7%, 26.6% and 21.4%, respectively. [ABSTRACT FROM AUTHOR]

Oxide inclusions significantly impeded the mechanical properties of the Wire and Arc Additive Manufacturing (WAAM) made high nitrogen Cr–Mn austenite stainless steels (HNSs). This paper focused on the inclusions' component, crystallization characteristics and formation mechanism. Results revealed that there are two types of inclusions: the round-shape nano-size inclusion (Type-I) and the micron-size island-shape inclusion (Type-II). The Type-I inclusion usually consists of the MnO particle or the combination of the MnO, Si-oxides and precipitations (MnS or Cr2N). Most of the Type-I oxide inclusion is located in the range between 300 nm and 700 nm,the number of Type-I oxide inclusion takes the main part of 69.7%.With higher content, smaller size and more even distributions, the isolated Type-I oxide inclusions would be beneficial to the mechanical properties owing to the Orowan strengthening mechanism. The Type-II inclusion is mostly composed of the MnO matrix and the coherent chromite spinel (MnCr2O4). In general, the larger the size, the more serious the negative impact on mechanical properties. And there was a strong negative correlation between the size and quantity of type II oxide inclusions. After heat treatment, abundant phase transformations occurred in the Type-II inclusions and some harmful phases (Sigma, MnS et cl.) were often found in or around the inclusions with specific orientation relationships. During deposition, the unstable droplet transformation and the trapped residual slag were the main causes for the inclusions in the molten pool.

The characteristics of composite inclusions between atomic interfaces has been investigated by combining high-angle annular dark field (HAADF) with first-principles computations. The characteristics of the composite inclusions reveal a core of Ca2Al2O5, with CaS and TiN adhering to its surface. According to mismatch degree theory and SEM characterization, the nucleation rate increases with a decreasing degree of mismatch. Notably, the adhesion work of the Ca2Al2O5/CaS interface is greater than that of the Ca2Al2O5/TiN interface, demonstrating the stronger bond strength of the Ca2Al2O5/CaS interface. The prediction of the lowest interfacial energy shows that a stable interface can form between Ca2Al2O5 and MX. Hence, Ca2Al2O5 can be effectively utilized as a nucleation side for CaS (TiN). The present work provides valuable theoretical and technical information for knowledge-based design and prediction of composite inclusion regulation for structural steels, especially for marine engineering steels.

In this study, the crystallization behavior of a CaO–MgO–Al 2 O 3 –SiO 2 based glass ceramics with Nb 2 O 5 addition was investigated by using DSC, XRD and TEM techniques. It was found that three crystalline phases, namely, CaNb 2 O 6 , diopside and Gehlenite (Ca 2 Al 2 SiO 7), were formed from the glass matrix during the crystallization heat treatment. The CaNb 2 O 6 phase was the first to precipitate from the glass matrix at around 850 °C, acting as a nucleating agent that facilitated the formation of Gehlenite (Ca 2 Al 2 SiO 7) at 900–950 °C. The TEM observation revealed a consistent orientation relationship between the CaNb 2 O 6 and the Gehlenite (Ca 2 Al 2 SiO 7) phases, indicating that CaNb 2 O 6 could induce the epitaxial growth of Gehlenite (Ca 2 Al 2 SiO 7). This result provides a new insight into the preparation of Gehlenite epitaxial films and glass ceramics. [ABSTRACT FROM AUTHOR]

The 12% Cr heat-resistant steel used for critical components of fossil-fired power plants works in high-temperature and high-pressure steam environments for a long time and inevitably undergoes a certain amount of plastic deformation during service. This plastic deformation will affect the microstructure and hot ductility of the heat-resistant steel and ultimately influence its service life. Therefore, the effect of hot compression deformation on microstructural evolution at 650°C was investigated in this work. As the amount of hot compression deformation increased, the number of subgrains significantly increased, and their sizes gradually decreased. When the amount of deformation reached 50%, dynamic recrystallization occurred, forming a preferred orientation in the rolling direction. and fiber texture appeared in the microstructure when the deformation amount reached 8%, and the intensity of texture was significantly higher than that of texture. Their intensity values further increased with the increase of the amount of deformation. As the amount of hot compression deformation increased, the deviation angle of the Kurdjumov–Sachs (KS) orientation relationship between M23C6 particles and α-Fe gradually increased. Their KS orientation relationship began to be disrupted at the deformation amount of 6% and was completely destroyed at the deformation amount of 20%. With the amount of deformation increasing up to 50%, there were no micropores at the M23C6/matrix interfaces, and no hot cracking occurred. This was mainly attributed to the occurrence of dynamic recrystallization which alleviated stress concentration at the particles /matrix interfaces. The mechanisms of microstructural evolution involving subgrains, grain boundary characteristics, texture evolution, strain distribution, and orientation relationship were discussed in detail.

Phase constituents and solidification microstructures of as-cast Fe7(CoNiMn)93-xBx (x = 9, 13) HEAs were investigated via electron backscattered diffraction and transmission electron microscopy. It was observed that the phase constituents contain an FCC1 solid solution and an M23B6 compound. The microstructure of hypoeutectic Fe7(CoNiMn)84B9 high-entropy alloy consists of primary face-centered-cubic (FCC1) dendrite and trigonal-shaped complex-regular eutectic, and that of Fe7(CoNiMn)80B13 eutectic high-entropy alloy is fully consisted of trigonal-shaped complex-regular eutectic. The formation of this rare complex-regular eutectic is attributed to the preferential growth of M23B6 in a trigonal-shaped trunk due to its crystallography anisotropy. In addition, the FCC1 eutectic phase has a cube-on-cube orientation relationship with the M23B6 phase where the same orientation but different lattice constants for them leads to the appearance of misfit dislocations at the interface, which enhances the strength of materials. The compression strength for Fe7(CoNiMn)80B13 eutectic high-entropy alloy is higher than that of hypoeutectic Fe7(CoNiMn)84B9 high-entropy alloy.

Faceted morphology is common in the microstructures resulting from solid-state phase transformations in a wide range of crystalline materials. This study explains the faceted interfaces based on the concept of singular interfaces, which are characterized by key interfacial structures at two levels: the singular dislocation structure and the preferred state existing between the dislocations. It identifies interface geometries required by these structures at two stages: before and after dislocation generation. Methods to determine the interface geometries are reviewed. These methods enable quantitative interpretation of phase transformation crystallography features, including the interface orientations and the orientation relationship between the two phases, irrespective of whether these features are described as rational or irrational. The agreement achieved across different systems indicates the crucial role of geometric matching in the development of phase transformation crystallography. An example is provided for an illustration of the application of the two-stage approach, especially with an analysis in reciprocal space using a superimposed diffraction pattern. [ABSTRACT FROM AUTHOR]

In the Al-Fe binary system, the Al13Fe3 phase as well as the Al13Fe4 phase has similar icosahedral building blocks like those appearing in quasicrystals. Therefore, it is of vital importance to clarify the formation process of these two phases. Coexistence of the Al13Fe3 and Al13Fe4 phases was discovered from the educts obtained with a nominal atomic ratio of Al/Fe of 9:2 by high-pressure sintering for the first time. Firstly, single crystal X-ray diffraction (SXRD) combined with a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) measurement capabilities were adopted to determine the detailed crystal structures of both phases, which were sharply refined with regard to Al13Fe3 and Al13Fe4. Secondly, the orientation relationship between Al13Fe3 and Al13Fe4 was directly deduced from the SXRD datasets and the coexistence structure model was consequently constructed. Finally, seven pairs of parallel atomic planes and their unique orientation relations were determined from the reconstructed reciprocal space precession images. In addition, the real space structure model of the intergrowth crystal along with one kind of interfacial atomic structure were constructed from the determined orientation relations between two phases. [ABSTRACT FROM AUTHOR]

Although the Al2Fe phase has similar decagonal-like atomic arrangements as that of the orthorhombic Al5Fe2 phase, no evidence for intergrowth samples of Al2Fe and Al5Fe2 has been reported. In the present work, the co-existence of Al2Fe and Al5Fe2 phases has been discovered from the educts obtained with a nominal atomic ratio of Al:Fe of 2:1 by arc melting. First, single-crystal X-ray diffraction (SXRD) as well as scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) measurements have been utilized to determine the exact crystal structures of both phases, which are refined to be Al12.48Fe6.52 and Al5.72Fe2, respectively. Second, the orientation relationship between Al2Fe and Al5Fe2 has been directly deduced from the SXRD data sets, and the co-existence structure model has been constructed. Finally, four pairs of parallel atomic planes and their unique orientation relations have been determined from the reconstructed reciprocal-space precession images of (0kl), (h0l), and (hk0) layers. In addition, one kind of interface atomic structure model is constructed by the orientation relations between two phases, correspondingly. [ABSTRACT FROM AUTHOR]

Explaining the crystallography of iron alloys martensite with a {225}γ habit plane remains a challenging task within the phenomenological theory of martensite crystallography. The purpose of this study is to re-examine the martensite formed in a Fe-8Cr-1.1C alloy using EBSD, which has a better angular resolution than the conventional transmission electron diffraction techniques previously used. The results show that the single morphological plates, which hold a near {225}γ habit plane, are bivariant composites made up of two twin-related variants. It is shown that a {113}γ plane is systematically parallel to one of the three common 112 α planes between the two twin-related crystals. This observation suggests that the lattice invariant strain of transformation occurs through a dislocation glide on the {113}γ 〈110〉γ system, rather than through twinning as is commonly accepted. Based on this assumption, the predictions of Bowles and Mackenzie's original theory are in good agreement with the crystallographic features of {225}γ martensite. Unexpectedly, it is the high shear solution of the theory that gives the most accurate experimental predictions. [ABSTRACT FROM AUTHOR]

M23C6 carbide can precipitate simultaneously on both sides of austenite grain boundary in Fe–15Mn–3Al-0.7C steel tempered at 600 °C. In this paper, the morphology and growth behavior of M23C6 are studied by means of OM, SEM and TEM. The results show that the morphology of M23C6 located on both sides of grain boundary is different. On one side of the grain boundary, the carbides appear to be dispersed and disconnected, each with an irregular particle-like morphology, while on the opposite side, they are dispersed along the grain boundary in a short-rod morphology, and the adjacent ones tend to join together to form a network structure. In fact, regardless of which side of the grain boundary the carbides are on, they exhibit a definite growth behavior, growing along the close-packed plane and grain boundary. Also, the morphology of M23C6 depends on the angle between the close-packed plane and the grain boundary. In addition, twin structures with the same orientation can be found in both austenite and M23C6. A notable distinction between them is that there is a flat twin plane in the austenite twin structure but not in the carbide twin structure. Therefore, this paper highlights that the formation of these two twin structures is different. The austenite twin structure is caused by quenching treatment, while the carbide twin structure is formed by a new method called “growing-contacting”.

Acicular ferrite (AF) has been regarded as the optimal microstructure in steel welds and heat affect zones (HAZs), because of its superior combination of strength and toughness. Although various aspects of AF have been investigated, the crystallographic characteristics of AF, including orientation relationship, variant selection and variant pairing, are still not fully studied. In this research, a Ti-deoxidized high strength low alloy steel was prepared and subjected to HAZ thermal cycle simulation tests to attain AF microstructure. Optical micrographs were obtained and EBSD mappings of AF microstructures were conducted. Through crystallographic analysis, the orientation relationship between AF and austenite was found close to that of bainite transformed at a high temperature (580 °C). In the AF microstructure, all 24 variants are formed and variant selection is nearly random. Compared with bainite, the variant pairing of AF is more random despite the slight favour of certain variant pairs. Most of the adjacent AF laths are from different close-packed plane (CP) groups, leading to the classic interlocking morphology. Meanwhile, a large number of neighbouring AF laths belong to different Bain groups, resulting in a high density of high angle grain boundaries (HAGBs). Intragranular nucleation of primary AF laths on inclusions contributes both to the high HAGB density and to the interlocking morphology of AF, while the sympathetic nucleation of secondary AF laths only contributes to the latter. These results suggest that to increase the HAGB density in AF, promoting the intragranular nucleation on inclusions is more important than enhancing the sympathetic nucleation.

Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship (OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg17Al12 precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy (TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg17Al12 precipitates and the matrix were revealed: OR−1:[21¯1¯0]α//[011¯]β,(011¯1)α//(011)β; OR−2:[21¯1¯0]α//[011¯]β,(0001)α1∘from(41¯1¯)β; OR−3:[21¯1¯0]α//[011¯]β,(0001)α//(011)β, and OR−4:[21¯1¯0]α//[011¯]β,(0001)α//(100)β. Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential.

Although the non-basal precipitates, those not parallel to the basal plane, are more effective to block basal slip in Mg-Al alloys, the crystallographic orientation relationship (OR) between these precipitates and the α-Mg matrix has not been well established. In this work, the crystallography of the non-basal Mg 17 Al 12 precipitates in AZ80 alloy was systematically investigated by transmission electron microscopy (TEM). By tilting to a suitable electron beam direction, different kinds of non-basal precipitates were recognized in TEM, and the following four new ORs between the non-basal Mg 17 Al 12 precipitates and the matrix were revealed: OR − 1 : [ 2 1 ¯ 1 ¯ 0 ] α / / [ 01 1 ¯ ] β , (01 1 ¯ 1) α / / (011) β ; OR − 2 : [ 2 1 ¯ 1 ¯ 0 ] α / / [ 01 1 ¯ ] β , (0001) α 1 ∘ from (4 1 ¯ 1 ¯) β ; OR − 3 : [ 2 1 ¯ 1 ¯ 0 ] α / / [ 01 1 ¯ ] β , (0001) α / / (011) β , and OR − 4 : [ 2 1 ¯ 1 ¯ 0 ] α / / [ 01 1 ¯ ] β , (0001) α / / (100) β. Furthermore, these ORs and their habit planes were explained using the edge-to-edge matching model. The findings in this work can provide some guidelines for designing the microstructure of Mg-Al alloys to enhance their precipitation hardening potential. [ABSTRACT FROM AUTHOR]

The pearlite formed in 100Mn13 high carbon high manganese steel after 1323 K water toughening subsequently 923 K aging treatment is studied by transmission electron microscope and high-resolution technique. The results show that the pearlite is composed of three phases, which are M3C lamellae, M7C3 lamellae, and ferrite lamellae, respectively, with the orientation relationships of ( 01 1 ¯ )α∥( 2 2 ¯ 1 ¯ )M7C3, ( 1 ¯ 01)α∥( 10 2 ¯ )M3C, ( 2 1 ¯ 1)M3C∥( 2 1 ¯ 3 ¯ )M7C3, [ 251 ]M3C∥[ 542 ]M7C3∥[ 111 ]α. And M7C3 is formed at the phase interface between M3C and α. The growth physical model of three-phase pearlite is proposed. [ABSTRACT FROM AUTHOR]

A systematic investigation on microstructural and crystallographic characteristics of martensite micro-variants in Ni54Mn25Ga20.9Dy0.1 ferromagnetic shape memory alloy was performed. The alloys exhibited a dual-phase microstructure consisting of self-accommodated tetragonal martensite and hexagonal Dy-rich dispersive precipitates. In each colony, four distinct micro-variants with different crystallographic-orientations existed, where the adjacent variant pairs connected by crossing-interfaces possessed a non-twinned relationship and other pairs connected by extending-interfaces were twin-related to each other. The corresponding twinning planes and directions were {112} and 〈111〉, respectively. Nevertheless, the twinning relationships of these twin-related micro-variant pairs were not perfect, which contained a small rotation. Interface analysis demonstrated that these two types of interface planes coincide with the orientation relationship planes and twinning planes of their connecting micro-variants, respectively. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing is a developing technique with numerous advantages and challenges to overcome. As with all manufacturing techniques, the specific raw materials and processing parameters used have a profound influence on microstructures and the resulting behavior of materials. It is important to understand the relationship between processing and microstructures of Ti to advance knowledge of Ti-alloys in the additive field. In this study, a face-centered cubic (FCC) phase was found in grade 2 commercially pure titanium specimens, additively manufactured with directed energy deposition in an argon atmosphere. Two scanning speeds (500 and 1000 mm/min) and three scanning patterns (cross-hatched and unidirectional patterns) were investigated. Electron backscatter diffraction and energy-dispersive X-ray spectroscopy were used for microstructural and compositional analysis. Inverse pole figure, phase, and kernel average misorientation (KAM) maps were analyzed in this work. Larger amounts of the FCC phase were found in the unidirectional scanning patterns for the slower scanning speed, while the cross-hatched pattern for both scanning speeds showed a lower amount of FCC. Higher KAM averages were present in the faster scanning speed specimens. According to EDS scans, small amounts of nitrogen were uniformly distributed throughout the specimens, leading to the possibility of interstitial content as a contributing factor for development of the observed FCC phase. However, there is no clear relationship between nitrogen and the FCC phase. The formation of this FCC phase could be connected to high densities of crystalline defects from processing, plastic deformation, or the distribution of interstitials in the AM structure. An unexpected Kurdjumow–Sachs-type orientation relationship between the parent beta phase and FCC phase was found, as 110 B C C ∥ 111 F C C , 111 B C C ∥ 110 F C C . [ABSTRACT FROM AUTHOR]

Cu–Ti alloys are candidates for replacing Cu–Be alloys owing to their excellent mechanical properties, bending properties, and stress relaxation resistance. However, the precipitation behavior of Cu–Ti alloys remains poorly understood. In this study, diffraction patterns, orientations, and morphologies of continuous and discontinuous precipitates in a Cu–3 wt% Ti (Cu–3Ti) alloy are investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). In the peak-aging condition, numerous rod-like nanosized continuous precipitates (CP) of β′-Cu4Ti are uniformly distributed in the Cu–3Ti alloy. The CP retain their tetragonal structure, and their orientation relationships with the matrix are determined as [001]Cu//[001]β' and (010)Cu//(310)β', exhibiting six variants. With increasing aging time, discontinuous precipitates (DP) of β-Cu4Ti grow at the grain boundaries, displaying an orthorhombic structure (a = 0.453 nm, b = 0.4342 nm, and c = 1.293 nm). The orientation relationships between the DP and the Cu-matrix are determined as (Laughlin and Cahn, 1975; Han et al., 2016; Datta and Soffa, 1976; Han et al., 2020; Huang et al., 2023; Soffa and Laughlin, 2004; Wang et al., 2021; Si et al., 2016; Markandeya et al., 2004; Nagarjuna et al., 2001) [1-10]Cu//[501]β and (111)Cu//(010)β. Typical diffraction pattern models of the CP and DP in different directions were simulated, and the simulations were in good agreement with the experimental data.

//Nbss and α-Nb5Si3 phases were detected. Meanwhile, Nb2C was observed, and the crystal forms of Nb5Si3 changed in the C-doped composites. Furthermore, micron-sized and nano-sized Nb2C particles were found in the Nbss layer. The orientation relationship of Nb2C phase and the surrounding Nbss was [001]Nbss//[010]Nb2C, (200) Nbss//(101) Nb2C. Additionally, with the addition of C, the compressive strength of the composites, at 1400 °C, and the fracture toughness increased from 310 MPa and 11.9 MPa·m1/2 to 330 MPa and 14.2 MPa·m1/2, respectively; the addition of C mainly resulted in solid solution strengthening. [ABSTRACT FROM AUTHOR]

In-situ observation and microstructure analysis were combined with the nanoindentation to study the effect of the orientation relationship between the σ and γ phases on the mechanical property of the 7Mo super austenite stainless steel. The results from the HRTEM and the nanoindentation indicate that the semi-coherent interface (111)γ // (001)σ (which is composed of several atomic layers in the absence of element segregation) produced by eutectic transformation, effectively improves the strength of the interface.

In the Al-Fe binary system, the Al13Fe3 phase as well as the Al13Fe4 phase has similar icosahedral building blocks like those appearing in quasicrystals. Therefore, it is of vital importance to clarify the formation process of these two phases. Coexistence of the Al13Fe3 and Al13Fe4 phases was discovered from the educts obtained with a nominal atomic ratio of Al/Fe of 9:2 by high-pressure sintering for the first time. Firstly, single crystal X-ray diffraction (SXRD) combined with a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) measurement capabilities were adopted to determine the detailed crystal structures of both phases, which were sharply refined with regard to Al13Fe3 and Al13Fe4. Secondly, the orientation relationship between Al13Fe3 and Al13Fe4 was directly deduced from the SXRD datasets and the coexistence structure model was consequently constructed. Finally, seven pairs of parallel atomic planes and their unique orientation relations were determined from the reconstructed reciprocal space precession images. In addition, the real space structure model of the intergrowth crystal along with one kind of interfacial atomic structure were constructed from the determined orientation relations between two phases.

Explaining the crystallography of iron alloys martensite with a {225}γ habit plane remains a challenging task within the phenomenological theory of martensite crystallography. The purpose of this study is to re-examine the martensite formed in a Fe-8Cr-1.1C alloy using EBSD, which has a better angular resolution than the conventional transmission electron diffraction techniques previously used. The results show that the single morphological plates, which hold a near {225}γ habit plane, are bivariant composites made up of two twin-related variants. It is shown that a {113}γ plane is systematically parallel to one of the three common 112α planes between the two twin-related crystals. This observation suggests that the lattice invariant strain of transformation occurs through a dislocation glide on the {113}γ ⟨110⟩γ system, rather than through twinning as is commonly accepted. Based on this assumption, the predictions of Bowles and Mackenzie’s original theory are in good agreement with the crystallographic features of {225}γ martensite. Unexpectedly, it is the high shear solution of the theory that gives the most accurate experimental predictions.

Although the Al2Fe phase has similar decagonal-like atomic arrangements as that of the orthorhombic Al5Fe2 phase, no evidence for intergrowth samples of Al2Fe and Al5Fe2 has been reported. In the present work, the co-existence of Al2Fe and Al5Fe2 phases has been discovered from the educts obtained with a nominal atomic ratio of Al:Fe of 2:1 by arc melting. First, single-crystal X-ray diffraction (SXRD) as well as scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) measurements have been utilized to determine the exact crystal structures of both phases, which are refined to be Al12.48Fe6.52 and Al5.72Fe2, respectively. Second, the orientation relationship between Al2Fe and Al5Fe2 has been directly deduced from the SXRD data sets, and the co-existence structure model has been constructed. Finally, four pairs of parallel atomic planes and their unique orientation relations have been determined from the reconstructed reciprocal-space precession images of (0kl), (h0l), and (hk0) layers. In addition, one kind of interface atomic structure model is constructed by the orientation relations between two phases, correspondingly.

In martensitic steels the distribution of C is fundamental for the technological material properties. However, the effect of Si on C segregation is not known in detail. In this study, the impact of Si on the microstructure of martensitic steels is investigated using scanning electron microscopy and the martensite/austenite orientation relationships are determined using electron backscatter diffraction and transmission Kikuchi diffraction. Transmission electron microscopy and selected area diffraction pattern analysis were used to analyse the intragranular substructure of the martensitic phase. Further, the effect of Si on the redistribution of C is investigated by atom probe tomography in combination with transmission Kikuchi diffraction measurements in order to obtain the local C distribution and correlate it with the crystallography. It was found that the Si addition forms a sigmoidal distribution at the phase boundary and functions as a barrier for C segregation, hence reduces C partitioning into the austenite, while a Si free alloy shows clear C partitioning. Further it was observed that stable C cluster formation occurs along fine twin boundaries in the martensite, inhibiting carbide formation and partitioning of the C into the austenite.

The purpose of this work is to analyze the relationship between the architecture of self-accommodation complexes (SACs) and the lattice syngony of martensite crystals. Self-accommodation complexes consist of a set of pairwise twinned domains, martensite crystals, which are crystallographically equivalent variants of the orientation relationship between austenite and martensite lattices. The simplest SACs for tetragonal, orthorhombic, rhombohedral, and monoclinic distortions of the cubic austenite lattice are calculated. It is shown that complete self-accommodation is possible only in complexes containing all variants of the orientation relationship simultaneously. The problem of the external faceting of the complexes is discussed. The reason for the formation of SACs is the minimization of elastic energy, i.e., the faceting is regulated by the energy of the interphase boundary. On the other hand, if the external surface of a SAC is a polyhedron, its symmetry should fit into the anisotropy of elastic properties of austenite. From symmetry considerations, it is clear that the polyhedron should be regular and have the same symmetry elements as the cubic lattice of austenite, and the symmetry axes of the cubic lattice of austenite should coincide with the symmetry axes of the polyhedron. Such polyhedrons are some of Platonic and Archimedean solids with axes of symmetry of the second, third, and fourth orders. A number of examples calculated in the article confirm the possibility of the existence of complexes in the form of these polyhedrons. [ABSTRACT FROM AUTHOR]

The determination of orientation relationships in dual or multi-phase materials is very important in the field of interface engineering for the design of materials with tailored properties. In this work, a code is developed for the automated and statistical analysis of the orientation relationship of electron backscatter diffraction data. The code is applied to the example of Fe-Ni-(Si)-C alloys containing lenticular martensite and retained austenite, and it is shown that the orientation relationship (OR) corresponds to the Greninger–Troiano OR and that a statistically reliable investigation of the OR between the retained austenite and the related martensite variants is feasible using the code developed in this study. [ABSTRACT FROM AUTHOR]

Coarse particles in Cu-0.39Cr-0.24Zr-0.12Ni-0.027Si alloy were studied with scanning electron microscopy and transmission electron microscopy. Three types of coarse particles were determined: a needle-like Cu5Zr intermetallic phase, a nearly spherical Cr9.1Si0.9 intermetallic phase and (Cu, Cr, Zr, Ni, Si)-rich lath complex particles. The crystallographic orientation relationships of the needle-like and nearly spherical coarse particles were also determined. The reasons for formation and the role of the coarse phases in Cu-Cr-Zr alloys are discussed, and some suggestions are proposed to control the coarse phases in the alloys. [ABSTRACT FROM AUTHOR]

The effect of extended intercritical annealing time on the changes of the microstructure and tensile properties is studied in a medium Mn steel. Nanosized lamellar structures are formed after intercritical annealing at 550 °C for 8 and 16 h; they consist of mainly tempered‐α′ martensite with retained austenite. Many cementite precipitates are observed in the tempered‐α′ martensite matrix and at the high‐angle boundaries. The orientation relationship between θ‐cementite and tempered‐α′ martensite is identified to be (01¯1)θ//(21¯1)tempered‐α′, [011]θ//[011]tempered‐α′, and [100]θ//[111¯]tempered‐α′. Fresh α′ martensite is detected between the tempered‐α′ martensite and austenite lamellae in the quenched specimens. The fresh α′ martensite is formed due to partial martensitic transformation of austenite upon cooling. The fractions of cementite and fresh α′ martensite increase with extended annealing time, leading to reduced austenite fraction after quenching. Additional baking treatment at 200 °C increases yield stress and elongation due to the stabilization of the austenite. This study provides a detailed understanding of these complex nanosized microstructures and discusses the key factors governing their yield stresses and work hardening behaviors. [ABSTRACT FROM AUTHOR]

Characterization of triple junctions has been performed by considering the disorientation angles among grains around triple junctions. The disorientation angles for each triple junction are called θmin, θmid and θmax, which satisfy θmin ≤ θmid ≤ θmax. Disorientation-angle diagrams that relates θmin and Σθi = θmin + θmid + θmax were constructed for the triple junctions in deformed and annealed aluminum. By comparing the disorientation-angle diagrams before and after grain growth, we found self-similarity of the distribution of the disorientation angles around the triple junctions during the grain growth. [ABSTRACT FROM AUTHOR]

Al–Ce eutectic alloy has attracted much attention due to its excellent heat resistance and castability. A large number of interfaces are contained in the Al–Ce eutectic alloy. As an intermediary connecting the aluminum matrix and the Al11Ce3 reinforcement phase, the interfaces play an important role in enhancing the strength and toughness of the alloy. In this paper, eutectic Al–Ce alloy was prepared, the orientation relationship at the Al11Ce3/Al interface and the interface structure were investigated. Classification of orientation relationship was proposed, and three orientation relationships were observed: OR1, [010]Al11Ce3//[001]Al, (00 1¯)Al11Ce3//(010)Al, (100)Al11Ce3//(1¯ 00)Al; OR2, [5 2¯ 0]Al11Ce3//[1 2¯ 1]Al, (001)Al11Ce3//(111)Al; OR3, [1¯ 13]Al11Ce3//[011]Al, (110)Al11Ce3//(100)Al, of which OR3 is a new orientation relationship reported for the first time. First-principle calculations suggest that Al11Ce3 is combined with Al through a Ce-terminated surface of (001)Al11Ce3. The electronic structure indicates that the interface between Al and Al11Ce3 are chemical adsorptions, and the two-phase interface has strong interaction. The strong interface between the reinforcing phase and Al matrix can effectively enhance the load transfer, thereby improving the strength of the material.

The factors affecting the stability of an initially single-phase body-centered cubic (BCC) HfNbTaTiZr solid solution are investigated by heat treatments at 900 °C up to 1000 h in different atmospheres. The BCC solid solution is stable but oxygen (O) contamination originating from the aging atmosphere leads to the co-precipitation of an O-enriched hexagonal close-packed (HCP) Hf-Zr-rich phase and a second Nb-Ta-rich BCC phase. As O from the atmosphere diffuses from the surface to the core of the sample at a much faster rate along grain boundaries than through the grain interior, this results in an inhomogeneous distribution of precipitates, which formed at grain boundaries by a monotectoid reaction. In contrast, coincidence-site-lattice boundaries are not affected by this transformation owing to their lower diffusivities and lower capacity for heterogeneous nucleation. Similar phases were observed in a HfNbTaTiZr enriched with 3 at.% O, thus confirming the role of oxygen in phase stability. In both alloys, the orientation relationship (OR) between the HCP and BCC phases is predominantly of Burgers type but our analyses further revealed the presence of two minor ORs. More interestingly, both alloys exhibit rod-shaped HCP precipitates in contrast to the plate-shaped precipitates observed in conventional Ti and Zr-based alloys. This result can be rationalized by calculations of elastic strain energy density, which suggest that the rods should grow along 〈100〉 BCC to minimize the elastic strain energy. Deviations of up to 20° from this theoretical direction were observed and are likely related to relaxation by misfit dislocations or by plastic deformation. [Display omitted] [ABSTRACT FROM AUTHOR]

The effect of Mn addition on microstructures and properties of as-cast NiAl bronze was systematically investigated in this study. Phase diagram calculations (CALPHAD) were employed to investigate the phase transformation process, composition, and fraction of Cu-10Al-5Fe-5Ni-xMn (x = 0, 1.5, 4.5, 7 wt%) alloys. With the increasing Mn element, the β phase region expands, and the precipitation temperature of κ Ⅲ phase increases while the κ Ⅳ phase decreases. The microstructure characterization and quantitative analysis reveal significant morphology changes. The polygonal α-Cu phase transforms to the acicular α-Cu phase while the fraction of κ Ⅲ phase increases. The atomic-scale interface between the κ Ⅲ /α and the composition of the κ Ⅲ phase are analyzed using transmission electron microscopy. The results indicate that the κ Ⅲ phase exhibits a Nishiyama-Wasserman (NW) orientation relationship with the α-Cu phase in Mn-containing alloys. Additionally, optimal mechanical properties of UTS = 795 MPa, YS = 438 MPa are achieved with the addition of 4.5 wt% Mn, while the best EL = 20.8 % is attained with 1.5 wt% Mn. • The effect of Mn addition on microstructures and properties of as-cast NiAl bronze was systematically investigated. • Phase diagram calculations (CALPHAD) were employed to investigate the phase transformation process. • The phase transformation in Cu-10Al-5Ni-5Fe-xMn alloys can be categorized into three cases. • The κ Ⅲ phase exhibits a Nishiyama-Wasserman (NW) orientation relationship with the α-Cu phase in Mn-containing alloys. [ABSTRACT FROM AUTHOR]

This study investigated the formation and growth of intra-granular ferrite with inclusions (TiN, MnS) in the heat-affected zone (HAZ) of a welding joint in low-carbon steels. The relationship between the cooling rate and the density and size of inclusions was analyzed. An orientation relationship akin to the Baker–Nutting relationship was identified between TiN and ferrite, while the orientation relationship between MnS and ferrite approximated the Kurdjumov–Sachs relationship. At low cooling rates, in the absence of nucleation support from TiN and MnS inclusions, the microstructure in the HAZ comprised Widmanstätten ferrite. Additionally, the shape, size, and density of primary ferrites and Widmanstätten ferrite in steels were influenced by sulfur content.