Observed Orientation Relationships Research Articles

Preparation of Oriented Nanoporous Magnetite Films by a Template-Free Solution Process from Iron Oxyhydroxide Films

Nanoporous oxide films composed of nanocrystal assemblies with an aligned crystallographic orientation are key nanostructures for efficient interfacial reactions. However, a simple, template-free method for their formation remains a challenge. Layered metal hydroxide (LMH) films are a promising precursor for spontaneous formation of nanoporous oxide films.[1-4] LMHs have a layered structure comprising 2D sheets of edge-shared octahedral hydroxide, i.e., brucite structure, with or without interlayer anions and water molecules. Calcination of LMH results in dehydration, anion elimination, and volume shrinkage, leading to the spontaneous formation of nanoporous oxides.In this study, we have prepared nanoporous and ferrimagnetic magnetite (Fe3O4) films by using layered iron hydroxides, namely, green rust (GR), as a precursor. Generally, GR has a brucite-type structure containing Fe2+ and Fe3+ ions, and is highly susceptible to oxidation by oxygen in water and air, leading to the formation of iron oxyhydroxides (FeOOH). Here, GR films were electrochemically deposited on FTO substrates in an aqueous solution containing Fe2+ and NO3 − ions at room temperature. Drying the GR films in air resulted in the formation of two-type FeOOH films, depending on the electrodeposition condition. Characterization using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and FT-IR spectroscopy revealed that one is [010]-oriented γ-FeOOH films, and the other is [001]-oriented δ-FeOOH films. The obtained FeOOH films had a mille-feuille like morphology with 500–700 nm thickness. Heat treatment of these two-type FeOOH films under vacuum at 500 °C resulted in the formation of [110]- and [111]-oriented nanoporous Fe3O4 films. The obtained Fe3O4 films showed a ferrimagnetic behavior in VSM measurements and had a nanoporous structure comprising nanoparticles with 50–100 nm diameter.Finally, a possilble interpretation for the observed orientation relationships between the FeOOH and Fe3O4 was also discussed on the basis of pyrolysis intermediates of FeOOH and similarity in their atomic arrangements. References T. Shinagawa, M. Watanabe, T. Mori, J.-i. Tani, M. Chigane and M. Izaki, Inorg. Chem., 57, 13137 (2018).T. Shinagawa, M. Chigane and M. Izaki, ACS Omega, 6, 2312 (2021).T. Shinagawa, M. Chigane and M. Takahashi, Cryst. Growth Des., 22, 4122 (2022).T. Shinagawa, N. Kotobuki and A. Ohtaka, Nanoscale Adv., 5, 96 (2023). Figure 1

Pattern formation via the oriented growth of Au-Si thin films on Si(001) substrate

The fabrication of patterned surfaces is integral to various device manufacturing processes. These techniques, developed over time, enable the precise manipulation of surface properties at the nanoscale. In this study, we introduce a self-driven approach for patterning metal and semiconductor surfaces by solidifying eutectic Au-Si thin films on Si(001) substrates. The resulting pattern encompasses meticulously aligned rectangular Au-Si eutectic structures and Si islands, the orientations of which are determined by the substrate. This exceptional alignment is attributed to the epitaxial growth of Si(001) and the heteroepitaxial growth of Au(001) and Au(011) within the films. This conclusion was corroborated through selected area electron diffraction and synchrotron radiation grazing-incidence wide-angle X-ray scattering (GIWAXS). We propose a 4:3 coincident site lattice (CSL) model to elucidate the Au-Si interface, explaining the dominant (001)[110]Au||(001)[110]Si orientation relationship that minimizes the Au/Si lattice mismatch to 0.2%. The other observed orientation relationships, (110)[001]Au||(001)[110]Si and (001)[010]Au||(001)[110]Si, entail a 6.3% mismatch in one or two directions, leading to contrasting elastic strains in the Au and Si lattices, accompanied by the accrual of elastic strain energy. This study underscores the practicality of substrate-oriented pattern formation, with potential applications in other phase-separated systems.

Effect of elastic deformations on direct polymorphic transformations in BN under pressure

This paper gives an investigation of the effect of shear deformation on direct transitions in BN under pressure. The transition of a hexagonal (graphite-like) phase h-BN into a cubic (“sphalerite”) c-BN through the intermediate rhombohedral phase r-BN, at a pressure P = 3.0 GPa, is shown. With shear deformation applied, the mechanism of h-BN transformation into the hexagonal (wurtzite) phase w-BN changes, and the following planes are parallel in the phases: for P = 5.0 GPa and deformation ε = 0° (001)h|| (001)w; and for P = 5.0 GPa and deformation ε ≅ 7.2 (001)h|| (100)w. The shear deformation at 6–17 GPa leads to the reverse transition of w-BN to h-BN and the observed orientation relationship is different from the one occurring at the thermal transformation of w-BN to h-BN (T ≅ 1600 K) at a pressure P = 0.1 MPa.

Bond strength between TiN coating and microstructural constituents of a high speed steel determined by first principle calculations

The adhesion of protective hard coatings to the substrate is one of the most important parameters that influence the performance of metal cutting tools. By a combination of high-resolution transmission electron microscopy and first principles modelling we determine the interface adhesion between a TiN hard coating and microstructural constituents of a high speed steel on an atomic level for the first time. Based on experimentally observed orientation relationships, multiple structures are studied for each interface and both interface cohesion and resistance to sliding are evaluated for MC and M6C carbides as well as the martensitic matrix to TiN coating. We find that TiN coatings have high adhesion to MC carbides, while lower adhesion is present for M6C and the martensitic matrix. Close agreement with experimental measurements validates this approach and suggests new strategies for developing steels with increased coating adhesion.

Co-deformation between the metallic matrix and intermetallic phases in a creep-resistant Mg-3.68Al-3.8Ca alloy

The microstructure of Mg-Al-Ca alloys consists of a hard intra- and intergranular eutectic Laves phase network embedded in a soft α-Mg matrix. For such heterogeneous microstructures, the mechanical response and co-deformation of both phases under external load are not yet fully understood. We therefore used nano- and microindentation in combination with electron microscopy to study the deformation behaviour of an Mg-3.68Al-3.8Ca alloy.We found that the hardness of the Mg2Ca phase was significantly larger than the α-Mg phase and stays constant within the measured temperature range. The strain rate sensitivity of the softer α-Mg phase and of the interfaces increased while activation volume decreased with temperature. The creep deformation of the Mg2Ca Laves phase was significantly lower than the α-Mg phase at 170 °C. Moreover, the deformation zone around and below microindents was dependant on the matrix orientation and was influenced by the presence of Laves phases. Most importantly, slip transfer from the α-Mg phase to the (Mg,Al)2Ca Laves phase occurred, carried by the basal planes. Based on the observed orientation relationship and active slip systems, a slip transfer mechanism from the soft α-Mg phase to the hard Laves phase is proposed. Further, we present implications for future alloy design strategies.

Automated reconstruction of parent austenite phase based on the optimum orientation relationship

Characterization of the austenite phase at high temperatures is important for understanding the microstructural evolution during steel processing. The austenite phase structure can be reconstructed from the room-temperature microstructure employing the crystallographic orientation relationship between the parent and product phases. The actual orientation relationships in steels are often calculated on the basis of well known relations (e.g. Kurdjumov–Sachs), which may differ from the experimentally observed orientation relationships. This work introduces a new approach to improve the current state of the art in prior phase reconstruction. The proposed approach consists of two new algorithms that are sequentially applied on an electron backscatter diffraction (EBSD) measured data set of the product phase microstructure: (i) an automated identification of the optimum orientation relationship using the observed misorientation distribution of the entire EBSD scan and (ii) reconstruction of the parent phase microstructure using a random walk clustering technique. The latter identifies groups of closely related grains according to their angular deviation from the proposed orientation relationship. The results were validated by near in situ experimental observations of phase transformation in an Fe–Ni alloy whereby the experimentally measured parent phase structure could be compared point by point with the reconstructed counterpart.

Formation of the cementite crystal in austenite by transformation of triangulated polyhedra.

A mechanism is proposed for the nucleus formation at the mutual transformation of austenite and cementite crystals. The mechanism is founded on the interpretation of the considered structures as crystallographic tiling onto non-intersecting rods of triangulated polyhedra. A 15-vertex fragment of this linear substructure of austenite (cementite) can be transformed by diagonal flipping in a rhombus consisting of two adjacent triangular faces into a 15-vertex fragment of cementite (austenite). In the case of the mutual austenite-cementite transformation, the mutual orientation of the initial and final fragments coincides with the Thomson-Howell orientation relationships which are experimentally observed [Thompson & Howell (1988). Scr. Metall. 22, 229-233] in steels. The observed orientation relationship between f.c.c. austenite and cementite is determined by a crystallographic group-subgroup relationship between transformation participants and noncrystallographic symmetry which determines the transformation of triangulated clusters of transformation participants. Sequential fulfillment of diagonal flipping in the 15-vertex fragments of linear substructure (these fragments are equivalent by translation) ensures the austenite-cementite transformation in the whole infinite crystal. The energy barrier for diagonal flipping in the rhombus with iron atoms in its vertices has been calculated using the Morse interatomic potential and is found to be equal to 162 kJ mol-1 at the face-centered cubic-body-centered cubic transformation temperature in iron.

Determination of minimal energy facet structures in Σ3 and Σ9 grain boundaries: Experiment and simulation

Grain boundary engineering (GBE) in FCC alloys relies on the presence of low-energy, coherent Σ3 boundaries to improve material performance. To make microstructures with a profuse network of Σ3 boundaries, a repetitive cycle of low-level deformation and followed by annealing is commonly employed. In this work, we use a combination of in situ SEM, in situ TEM, and a relaxation theory for grain boundaries to investigate the structural states of grain boundaries in Cu after a cycle or many cycles of deformation and annealing steps. It is revealed that during annealing the orientation relationships and boundary morphology of deformed Σ3 and higher order variants, Σ9 boundaries, change appreciably, from being curved to distinctly, crystallographically faceted. The theoretical analysis identifies the faceting process and the crystallography of the facets as corresponding to the optimal, low-energy structures for the observed orientation relationships. It is, therefore, shown that post-deformation heat treatments used in GBE are recovering the highly deviated and deformed Σ3s boundaries to a low-energy state.

The Prediction of Carbothermal Reduction Reaction Induced Ti4O7/Ti5O9 Interface Structures in Titanium Oxide Nanosystems

AbstractThe reduced titanium oxide (TinO2n‐1, 4 ≤ n ≤ 10) material system has attracted considerable attention due to their unique crystal structure and excellent electrical and chemical properties. Interface science and engineering play a very important role in both the synthesis or usage of such material, not only because the commonly observed multiphase coexistence phenomenon during the preparation process, but also due to the special physical and chemical properties brought by the heterogeneous interfaces. The lack of research on the interface structures as well as their influence on the properties seriously hinders the development of TinO2n‐1. In this work, crystallographic model is employed first to predict the crystallographic features of Ti5O9/Ti4O7 interface in titanium oxide nanosystems. The initial lattice correspondence is determined after fully considering the crystal symmetry and structures of Ti5O9 and Ti4O7. To verify the predicted results, Ti5O9/Ti4O7 nanocomposites are prepared through carbothermal reduction reaction, followed by detailed X‐ray diffraction and transmission electron microscopy characterizations. The observed orientation relationships between Ti5O9 and Ti4O7 are consistent with the predicted results, which confirm the application of crystallographic model in the phase transformation in which chemical reaction involved.

Misorientation distribution between martensite and austenite in Fe-31 wt%Ni-0.01 wt%C

We characterized the morphology, substructure and crystallography of lenticular martensite in a Fe-Ni-C alloy by means of electron backscatter diffraction and scanning electron microscopy. Electron backscatter diffraction maps were used to determine the orientation relationship between austenite and martensite across large regions of the microstructure. We employed orientation distribution functions as a statistical representation method for the observed orientation relationships. High-resolution point-to-point scans were used to normalize the effects of the orientation changes in the austenite caused by the plastic deformation during the formation of lenticular martensite. The analysis revealed that most of the transformation in this material follows an orientation relationship close to the one proposed by Greninger and Troiano.

Investigation of the crystallographic orientations of the β-Mg17Al12 precipitates in an Mg-Al-Zn-Sn alloy

The crystallographic orientation relationships between β-Mg17Al12 precipitates and α-Mg matrix were investigated in the Mg-Al-Zn-Sn alloy. New orientation relationships were observed and the growth direction of the particles with new orientation relationships was along the [0002]α direction of the magnesium matrix. One of the orientation relationships was analyzed and identified as 12̅10α//111̅β,0001α//12̅1̅β. The stereographic projection of the newly observed orientation relationship was calculated and discussed. Moreover, the interfaces between the β-Mg17Al12 precipitates and α-Mg matrix and two β-Mg17Al12 particles were studied.

Orientation relationships, interface structures, and mechanical properties of directionally solidified MoSi2/Mo5Si3/Mo5Si3C composites

The microstructures, orientation relationships, and high-temperature deformation behavior of directionally solidified (DS) ingots of MoSi2/Mo5Si3/Mo5Si3C three-phase eutectic composites were investigated. The DS three-phase composites exhibit a fine and homogeneous script lamellar microstructure. Mo5Si3 and Mo5Si3C individually form interconnected networks that extend in the growth direction (GD) of the MoSi2 matrix and maintain [11¯0]MoSi2, [001]Mo5Si3, and [0001]Mo5Si3C approximately parallel to the GD. High-temperature strength is higher in the DS three-phase composite than in the binary two-phase counterpart, especially below 1200 °C. This is mainly because of MoSi2 matrix refinement and the presence of the strengthening phase Mo5Si3C. The observed orientation relationship between component phases is discussed in relation to lattice misfits.

Fully automated orientation relationship calculation and prior austenite reconstruction by random walk clustering

Two new methods, one for determining the experimentally observed Orientation Relationship (OR) and another for reconstructing prior austenite phase, are proposed. Both methods are based on the angular deviation of the OR at the grain boundaries. The first algorithm identifies the optimum OR using the misorientation distribution of the entire scan i.e. without manual selection of parent grains. The second algorithm reconstructs the parent phase using a random walk clustering technique that identifies groups of closely related grains based on their angular deviation of the OR.

Orientation Studies of α-Al(Fe,Mn)Si Dispersoids in 3xxx Al Alloys

Dispersoids are important in 3xxx Al alloys, influencing mechanical properties, texture and recrystallization. In this work α-Al (Fe,Mn)Si dispersoids have been studied after low temperature homogenisation. The common orientation relationship between dispersoids and Al matrix has been reported in earlier studies. Here a systematic study on the orientation relationship and its exceptions is presented. It is found that most of the dispersoids follow the common orientation relationship, [1-1 1] α //[1-1 1]Al , (5-2 -7 ) α //(0 1 1)Al . Here the dispersoids are semi coherent with the Aluminum matrix. Different morphologies and habit planes are possible. Deviations from the most commonly observed orientation relationships are presented and discussed, to underline the complexity of the phase and its relation to the matrix.

Crystallography of phase transitions in metastable titanium aluminium nitride nanocomposites

The isostructural decomposition of the titanium aluminium nitride supersaturated solid solution crystallising in the face centred cubic (fcc) crystal structure into the titanium-rich fcc-(Ti,Al)N and almost titanium-free fcc-(Al,Ti)N and the transformation of metastable fcc-(Ti,Al)N into the wurtzitic aluminium nitride are discussed from the crystallographic point of view by taking the observed orientation relationships between the adjacent phases into account. It is shown that the isostructural decomposition of fcc-(Ti,Al)N into Ti-rich fcc-(Ti,Al)N and fcc-(Al,Ti)N and the transformation of the metastable fcc-(Ti,Al)N into the thermodynamically stable wurtzitic phase are concurrent processes, which are controlled not only by the thermodynamic stability of the respective compound and by the diffusivity of Al and Ti, but also by the local lattice strains. A part of the local lattice strains is regarded to result from the lattice misfit at the interfaces between the titanium aluminium nitrides having different [Al]/[Ti] concentration ratios and, in the case of the fcc/wurtzite-type interface, also having different crystal structures. The phase transition of the fcc-(Ti,Al)N to the wurtzitic one was predicted to be facilitated by stacking faults. The results of crystallographic considerations were verified experimentally by using in situ high-temperature synchrotron diffraction experiments that were performed on cathodic arc evaporated (Ti,Al)N thin films containing titanium and aluminium in different amounts.

Discontinuous precipitation of Co3V in a complex Co-based alloy

Discontinuous precipitation of chromium-rich Co3V lamellae has been found in a Co-based alloy containing 2 wt% V after prolonged ageing at 800 {\\degr}C. This discontinuous precipitation is associated with a noticeable redistribution of alloying elements in the alloy relative to those parts of the aged alloy that preserve the c.c.p.-L12 microstructure found in the as-cast and homogenized condition. The orientation relationship between the c.c.p. Co-rich matrix and these hexagonal phase chromium-rich Co3V precipitates is shown to be || and [1 1 1]Co || , i.e. || and [1 1 1]Co || in the four-index notation. 3 × 3 transformation matrices relating directions and planes in the two phases have been established. The observed orientation relationship between the two phases is consistent with low lattice misfit between the two phases.

Prediction of the morphology of Mg32(Al, Zn)49 precipitates in a Mg–Zn–Al alloy

A geometrical model has been applied to predict the morphology of faceted Mg32(Al, Zn)49 precipitates in a Mg–Zn–Al alloy using the observed orientation relationship (OR) and the lattice parameters of the precipitates and the matrix as inputs. Planes in rational or in irrational orientations with higher densities of good matching sites are more likely to be preferred, which agrees well with experimental observations.

Crystallography of Mg2Sn precipitates with two newly observed orientation relationships in an Mg–Sn–Mn alloy

Two new orientation relationships between β-Mg2Sn precipitates and α-Mg matrix have been observed by transmission electron microscopy. One is (1 1 0)β//(0 0 0 1)α, [0 0 1]β//[1 −1 0 0]α, and the other is (1 1 0)β//(0 0 0 1)α, [−1 1 −1]β//[1 −1 0 0]α. The precipitates with both orientation relationships exhibit a lath shaped morphology, with the long axis lying along [1 1 −2 0]α. The morphology is interpreted by a three-dimensional near coincidence sites model.

Orientation relationships between phases arising during compression testing in ZrO2–TRIP-steel composites

Abstract The martensitic transformations taking place during the compressive deformation of a TRIP-steel matrix with zirconia particles are investigated using EBSD, and the orientation relationships are discussed. In the TRIP-steel matrix, the mutual orientation of austenite and ɛ -martensite fulfils the Shoji–Nishiyama orientation relationship perfectly, whereas the γ – α ’ transformation is characterised by the Kurdjumow–Sachs orientation relationship with a small deviation. This behaviour is attributed to the different formation mechanisms of ɛ - and α ’-martensites. Whereas the ɛ -martensite is interlaced through faulting of the austenite crystal lattice, α ’-martensite forms new domains. Particularly at the void-free interfaces between the TRIP-steel and the ceramic particles in virgin samples, the external load can be transferred to the ceramic particles. As a consequence, a stress induced phase transformation within the MgO partly stabilised ZrO 2 can be observed. Different observed orientation relationships in ZrO 2 are discussed with respect to two possible t-ZrO 2 unit cell choices. Slight deviations from the ideal orientation relationship of approximately 1–2° are necessary for a better coherence between t-ZrO 2 and m-ZrO 2 because of their lattice misfit. The resulting mechanical properties are shown in context to the arising volume fraction of the martensitic phases.

Microstructure and Crystallographic Features of Martensite Transformed from Ultrafine-Grained Austenite in Fe–24Ni–0.3C Alloy

We studied microstructure and crystallographic features, especially orientation relationship, of martensite transformed from austenite with mean grain sizes ranging from 35μm to 750 nm in an Fe­24Ni­0.3C alloy. The austenite structures with ultrafine or fine grains were fabricated through intense straining by accumulative roll-bonding process and subsequent annealing. The morphology of martensite transformed from the austenite with various grain sizes was all lenticular type. On the other hand, the martensite plate size decreased with the decrease in the austenite grain size. The orientation relationship of martensite transformed from coarse-grained austenite with mean grain size (d) of 35μm changed depending on the location within martensite plate: i.e., it was Greninger­Troiano relationship at the center part of each martensite plate, while it changed to Kurdjumov­Sachs relationship near the interphase boundary. In contrast, the whole area of each martensite plate, transformed from fine-grained austenite (d = 2.5 μm) and ultrafine-grained austenite (d = 750 nm), satisfied Greninger­Troiano relationship. Furthermore, high density of dislocations and low angle boundaries within the ultrafine-grained austenite resulted in a large scatter of observed orientation relationship. [doi:10.2320/matertrans.MD201121]