Cr Precipitate Research Articles

Microstructure and mechanical properties of ZrB2 ceramic particle reinforced AlCoCrFeNi high entropy alloy composite materials prepared by spark plasma sintering

In this study, xZrB2-AlCoCrFeNi (x = 0,5,10,15) (wt%) based high entropy alloy (HEA) composites were prepared by Spark Plasma Sintering (SPS). The influence of ceramic particle ZrB2 content on the densification behavior, microstructural evolution, and mechanical properties of the composites was investigated through scanning electron microscopy, X-ray diffraction, and mechanical performance testing. The results indicate that the HEA composites undergo a phase transformation, from (FCC + BCC + B2) structure to (FCC + BCC + B2+Laves) structure with the addition of ZrB2. The incorporation of ZrB2 facilitates the emergence of the Cr precipitate phase, and the grain size of this phase enlarges as the ZrB2 content rises. Additionally, when the ZrB2 content is 10 %, the maximum compressive strength reached 2071 MPa. Furthermore, at the ZrB2 content of 15 %, the composite material achieves a maximum densification of 99.13 % and a maximum hardness of 1222.2 HV.

Correlating microstructure and mechanical properties of harvested high dose Zorita light water reactor internals

In this study, microstructural studies and micro-mechanical testing of an ex-plant material harvested from the decommissioned pressurized water reactor (PWR) is carried out. Irradiated 304 stainless steel (SS) components were harvested by the Electric Power Research Institute, U.S. Nuclear Regulatory Commission, and members of the José Cabrera Nuclear Power Station (Zorita) in Spain. The bi-crystalline micro-tensile specimens, atom probe tomography (APT) tips, and transmission electron microscopy (TEM) lamellae were fabricated from the baffle plate materials irradiated to 0.05, 15 and 50 dpa to elucidate microstructural, microchemical, and local mechanical properties changes as a function of dose. TEM and APT studies reveal radiation induced Ni, Cr, and Si rich precipitates in the 15 dpa sample that become smaller and partially redissolve into the matrix of the 50 dpa sample (decreasing size and number density). Dislocation loop and cavity number density and size were quantified as a function of dose as well as swelling. Intergranular Ni and Si enrichments with concomitant Fe and Cr depletion were observed in the 15 dpa sample and were more pronounced in the 50 dpa sample. Micro-tensile testing performed in the scanning electron microscope (SEM) at room temperature and 300 °C shows that the material's local yield strength and ultimate tensile strength decreases with increased dose and elevated test temperature and provides further insights via localized strain mapping. Current and previous mechanical data was compared with calculated values using the dispersed barrier hardening model with inputs of dislocation loops, precipitates, and cavities from microstructural characterization.

Atomic simulation study on the effect of defects on nano-cutting mechanism of single crystal copper

Due to the high surface roughness of the parts produced by additive manufacturing (AM), the subsequent mechanical processing is required. The combination of additive manufacturing and micro/nano processing is the development trend of hybrid manufacturing in the future. In this work, the molecular dynamics simulation is used to study the effect and mechanism of different types of defects on copper cutting performance, including pore, Cr precipitate and diamond inclusion. The results show that the presence of defects leads to a decrease in the quality of the machined surface, while pore and diamond inclusion could lead to the appearance of deep holes on the machined surface. The phenomenon of sticking knife caused by stress concentration and high temperature at the tool tip is observed during the simulation in the model with Cr precipiate. The addition of defects causes a change in the horizontal cutting force. The highest force emerges during the simulation in the model with diamond inclusion. Defects in the copper substrate could reduce surface quality. Precipitate and inclusion could increase the stress near the tool so as to exacerbate tool wear and reduce tool life. Therefore, it’s necessary to decrease the number of defects in the matrix and to improve its cutting resistance.

Microstructural Evolution and Mechanical Properties of a Ni-Based Alloy with High Boron Content for the Pre-Sintered Preform (PSP) Application

The pre-sintered preform (PSP) is an advanced technology for repairing the Ni-based superalloy blade in a turbine. In general, boron is added to the Ni-based superalloys in small quantities (<0.1 wt.%) to increase boundary strength and cohesivity. Despite this, the effect of high B content (>1.0 wt.%) on the microstructure evolution and mechanical properties in Ni-based superalloys for the PSP application is rarely studied. The variety, composition and evolution of the precipitates during solution heat treatment in the alloy with high B content were determined by EBSD, EPMA and SEM. The results indicate that Cr, W and Mo-rich M5B3 type borides precipitate from the matrix and its area fraction reaches up to about 8%. The area fraction of boride decreases with the prolonging of solution time and the increase of temperature higher than 1120 °C. The borides nearly disappear after solution treatment at 1160 °C for 2 h. The redissolution of boride and eutectic results in the formation of B-rich area with low incipient melting (about 1189 °C). It can bond metallurgically with the blade under the melting point of the blade, which decreases the precipitation of harmful phases of the blade after PSP repairing. The microhardness within the grain in the PSP work-blank first decreases (lower than 1160 °C) and then increases (higher than 1185 °C) with the increase of solution heat treatment temperature due to the dissolving and precipitation of borides. The tensile strength of the combination of PSP work-blank and Mar-M247 matrix at room temperature after solution treatment is related to the area fraction of boride, incipient melting and the cohesion between PSP work-blank and Mar-M247 matrix.

Enhanced mechanical properties and strengthening mechanism of Cu-Ni-Si alloy with trace chromium addition

Cu-3Ni-0.7Si-xCr-0.05Mg (x = 0.1 and 0.4) (wt% nominal composition) alloys were fabricated to investigate the effect of Cr contents on properties evolution and precipitation behavior of Cu-Ni-Si alloy. The results of the property analysis show that trace addition of 0.1 wt% Cr element contributes a better strength (ultimate tensile strength of 823 MPa) after single cold rolling and aging treatment. The precipitation behavior is characterized by transmission electron microscopy. It is found that nanoscale FCC structural Cr precipitates shift into submicron Cr3Si particles with Cr content increasing from 0.1 wt% to 0.4 wt%. Meanwhile, such superior formation of Cr3Si particle decreases the fraction of δ-Ni2Si owing to quick consumption of Si element from Cu matrix. Further quantitative analysis of various strengthening mechanisms reveals that the changed precipitation behavior notably affects their strengthening contribution to Cr contained alloys, resulting in an increase of more than 5.6% in the Orowan-Ashby mechanism. Surprisingly, in the case of the aging state at a temperature of 460 °C for a duration of 2 h, it is confirmed that although a much larger strengthening effect origins from nanosized δ-Ni2Si precipitate, the strength variation relies more on the Cr precipitation. That is, the lower strength at higher Cr content is mainly caused by the lower strengthening effect from Cr element related phases. In addition, the effect of the addition of trace Cr element on the operating mechanism on conductivity is also clarified. The results are expected to provide an appropriate content of Cr element and a dependable processing theory guidance for improving the comprehensive properties of the Cu-Ni-Si alloys.

Synergetic effect of piled-up material around the nanoindentation cavity on additively manufactured Cu-Cr-Zr alloy

The Cu-Cr-Zr alloy lost its hardness during the supply of power to pantograph assembly in railways applications. The present study focused on the influence of piled-up material on the nanohardness behavior of Laser Powder Bed Fusion (LPBF) produced Cu-Cr-Zr alloy. The 100 indentations were carried out at 3000 µN, 6000 µN and 9000 µN loads with the pitch distance of 1 µm and 2 µm. Electron back scatter diffraction (EBSD) analysis revealed that the crystallography texture formed on (100), (101) and (111) planes. The X-ray photoelectron spectroscopy (XPS) analysis on the indentation revealed the formation of CuO, Cu2O and CuCr2O4 oxide layers. The material lost 6.3% of nanohardness when the load was increased from 3000 µN to 9000 µN without the influence of piled-up material. However, the material at 9000 µN exhibited 26.38% more nanohardness than 3000 µN. The Cr precipitate resisted the indentation against the deformation of the behavior up to 3000 µN. The nanohardness at 9000 µN increased with the increase of the row and columns other than the first column due to the irregular mixing of front and side piled-up material. The nanohardness values at 6000 µN and 9000 µN will be lost as the piled-up material has no metallurgical bonding with the substrate. More CuO, Cu2O and CuCr2O4 oxide debris formed at 9000 µN conditions than the other two load conditions.

Selective and Efficient Photoextraction of Aqueous Cr(VI) as a Solid-State Polyhydroxy Cr(V) Complex for Environmental Remediation and Resource Recovery

Aqueous hexavalent chromium (Cr(VI)) treatment and chromium resource recovery toward Cr-containing wastes are of significant importance and necessity to both wastewater remediation and resource recovery. Herein, via mild photoreaction conditions with isopropanol (IPA) as an electron donor, a catalyst-free strategy for aqueous Cr(VI) extraction to form an insoluble polyhydroxy Cr(V) complex is developed for the first time. Aqueous Cr(VI) with concentration from 5 to 150 ppm can be efficiently extracted with high selectivity even in the presence of coexisting ions, and the total Cr concentration in residue solution can be as low as 0.5 ppm. The Cr resource could be efficiently recovered as pure Cr2O3 by calcinating the resulting Cr(V) precipitate. Outstanding extraction efficiency could be realized with various IPA concentrations (1.3-12.0 mol/L) by coordinately tuning the pH value to promote the formation of Cr(VI)-IPA ester. The formed ester undergoes intramolecular electron transition under visible light irradiation, resulting in a polyhydroxy solid-state Cr(V) intermediate complex. The controlled pH value blocks further reduction of Cr(V) to soluble Cr(III); thus the insoluble Cr(V) intermediate complex is stabilized thermodynamically under ambient conditions. Because of its electric neutrality property and the strong intermolecule interaction via hydrogen bonds, a dioxo-bridged di-nuclear Cr(V) complex {Cr2(μ-O)2(OH)4[OCH(CH3)2]2} is finally precipitated as the main product. Satisfactory extraction and recovery of Cr from chromium-plating wastewater and discarded stainless steel verify that this approach is ideal for both one-step purification of Cr(VI)-containing wastewater and selective resource recovery from Cr-containing solid wastes in practical application.

Ethane-driven chromate and nitrate bioreductions in a membrane biofilm reactor

Chromium (Cr(VI)) and co-contaminating nitrate (NO3–) pose major threats to human health. Hydrogen- and methane-driven Cr(VI) and NO3– bioreductions have been documented, but unknown is whether or not non-methane short-chain gaseous alkanes (SCGAs), such as ethane (C2H6), also can drive Cr(VI) and NO3– reductions. This study demonstrated simultaneous Cr(VI) and NO3– bioreductions driven by C2H6 oxidation in a membrane biofilm reactor (MBfR) that delivered C2H6 directly to a biofilm by its diffusion through non-porous membranes. Scanning electron microscopy and X-ray photoelectron spectroscopy showed that the biofilm was mainly composed of cocci and bacillus and that a Cr(III) precipitate was the major product of microbial Cr(VI) reduction. Microbial community analysis showed that the C2H6-oxidizing bacterium Mycobacterium oxidized C2H6 and delivered organic intermediates to Cr(VI)-reducing bacteria TM7a, Sediminibacterium, and Deinococcus. Because the first step of ethane catabolism is a monooxygenation, the influent had to have dissolved oxygen, and the dominant respiratory process was O2 reduction. By providing insights into how Cr(VI) and NO3– bioreductions can be driven by C2H6 oxidation, these finding support the application of SCGAs for ex-situ bioremediation of waters contaminated with Cr(VI) and NO3–.

Mapping defects during phase transformation in high Cr content NiCr solid-solution through positron trapping

Understanding the role of point defects towards hardening –and influence on secondary phase evolution demands a systematic investigation of defects during aging. In the present work, we investigate defects present/evolved during thermal aging in high Cr content NiCr solid-solution using positron annihilation lifetime and coincidence Doppler broadening spectroscopy. Thermal aging at the studied temperature results in phase transformation of the matrix primarily by discontinuous precipitation leading to Cr precipitation as revealed from field-effect scanning electron microscopy. Positron annihilation results reveal that non-equilibrium thermal (excess) vacancies are predominant defects in the studied alloy. These vacancies are retained in the alloy due to the formation of vacancy-solute complex. During solutionization treatment, the excess vacancies are largely recovered attaining an equilibrium vacancy concentration. On the other hand, excess vacancies are not recovered during thermal aging and stable up to 24 h aging period. In addition to vacancy-solute complex, dislocations are evolved at higher aging times and suggested to be present at the interface of Cr precipitate and matrix. Under the consideration of positron trapping model, the estimated atomic concentration of vacancies (vacancy-solute complex) in the phase transformed NiCr is ~ 10−5 and the dislocation density is ~ 4 × 109 cm−2.

A model experiment on nano-particle stability in 12Cr-ODS steel using high-resolution high voltage microscopy

In this work, the microstructure stability of 12Cr-ODS ferritic steel under irradiation is studied using a high-resolution high voltage electron microscope up to 1.5 dpa at 300 and 500 °C. Coherent YTiO3 nanoparticles (NPs) undergo coarsening during electron irradiation and the coarsening rate is positively correlated to irradiation temperature (the third power of NPs size is proportional to the irradiation dose). He pre-implantation can significantly reduce the coarsening rate. A model coupling Ostwald ripening and irradiation enhanced diffusion is used to explain this coarsening. The fitting results between NPs size and irradiation dose show that pre-implanted He causes a lower diffusion of Y in 12Cr-ODS steel compared with the non-implanted sample. In response to the irradiation, plate-like radiation-induced precipitates appear which result in diffraction streaks in fast fourier transform (FFT) pattern. Precipitations are paralleled to [100] or [110] direction of Fe matrix and located near the interface between NPs and matrix. The hypothesis that coherent Cr precipitate along NPs/matrix interface caused diffraction streaks is proposed. Besides, He pre-implantation can also delay this precipitation.

Nanocompound-induced anti-softening mechanisms: Application to CuCr alloys

A nanocompound-induced anti-softening mechanism is proposed for preparing high strength and high conductivity CuCr alloys with favorable softening resistance. The mechanism is to introduce nanocompound at the Cu/Cr interface to suppress the coarsening of Cr precipitate. To verify the mechanism, Co and Ti are added to the CuCr alloy. CoTi compounds precipitate around the Cr precipitates after aging treatment. The coarsening of Cr and CoTi phases are both suppressed thanks to the low diffusion rates of Co and Ti atoms in Cu. Additionally, Cr and CoTi precipitates also inhibit the recrystallization. As a result, the CuCrCoTi alloy displays a higher softening temperature (>600 °C) than CuCr alloys.

Cyclic metallurgical process for extracting V and Cr from vanadium slag: Part II. Separation and recovery of Cr from vanadium precipitated solution

Cyclic metallurgical process for separation and recovery of Cr from vanadium precipitated solution by precipitation with PbCO3 and leaching with Na2CO3 was investigated. The concentration of Cr residue in the solution decreases from 2.360 to 0.001 g/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio of 2.5, adjusting the pH to 3.0 and stirring for 180 min at 30 °C. Then, the precipitates were leached with hot Na2CO3 solution to obtain leaching solution containing Na2CrO4 and leaching residue containing PbCO3. The leaching efficiency of Cr reaches 96.43% by adding the precipitates into 0.5 mol/L Na2CO3 solution with the mass ratio of liquid to solid (L/S) of 10:1 mL/g and stirring for 60 min under pH 9.5 at 70 °C. After filtration, leaching residue is reused in Cr precipitation and leaching solution is used to circularly leach the Cr precipitates until Na2CrO4 approaches the saturation. Finally, the product of Na2CrO4·4H2O is obtained by evaporation and crystallization of leaching solution.

Wear-resistance enhancement of nanostructured W-Cu-Cr composites

Nanostructured W-Cu-Cr composites were fabricated, which exhibit exceptionally high hardness (~1000 HV) as compared with those of the conventional W-Cu composites, due to the combined advantages of Cr dissolution, precipitate formation and grain refinement. Nonmonotonic variation of the wear resistance with hardness was discovered. With an appropriate content of Cr, the preferential oxidation reduced the oxidation of W. Moreover, it facilitated formation of a stable protective film with fish-scale morphology and also refined the structure, leading to a high microhardness at the worn surface. The wear rate (1.65 × 10−6 mm3 N−1 m−1) was reduced by an order of magnitude compared with that of the conventional counterpart. However, excessive addition of Cr may deteriorate the wear resistance in spite of a higher hardness due to the embrittlening of W phase and difficulty to form a stable protective film at the worn surface. This study provides a new strategy for developing W-Cu composites with outstanding wear resistance.

Structure, magnetism, electronic properties and high magnetic-field-induced stability of alloy carbide M7C3

Previous experiments have proven that a high magnetic field can make alloy carbide M7C3 (M = Fe, Cr) precipitate ahead of time at intermediate temperatures. First-principles calculations are employed to search the source of magnetic-field-induced alloy carbides precipitation behaviors of orthorhombic M7C3. The basic building units for M7C3 crystals are polyhedrons formed by metal atoms and C atoms. The framework structure of o-M7C3 consists of metal tetrahedrons, metal octahedrons and triangular metal prisms. Magnetic calculations show that the substitution of Cr atoms causes the magnetic moments of the Fe atoms to decrease to different extents. Moreover, Cr atoms also have a magnetic moment antiparallel to the Fe atoms. Electronic structure calculations indicate that the bonds in M7C3 are a mixture of ionic, covalent and metal bonds. The substitution of Cr atoms weakens the ionic and covalent bonds between the Fe and C atoms; however, strengthen the metal bonds between the Fe and Cr atoms. The magnetic free energy change of M7C3 is larger than that of M2C and M3C at 823 K with a 12 Tesla field, which agrees well with the experimental results for a magnetic field promoting the precipitation of M7C3. This study provides a theoretical basis for the precipitation behaviors induced by magnetic fields in steels.

In-situ hybrid Cr3C2 and γ′-Ni3(Al, Cr) strengthened Ni matrix composites: Microstructure and enhanced properties

Mechanical properties of Ni-based superalloys strongly depend on γ′-Ni3Al precipitates and hard particles. However, the traditional Ni-based composites have reached the serviceability limit as to satisfy the requirement of higher speed and thrust to weight ratio for advanced aerospace engines. Herein, we successfully fabricated a novel in-situ Cr3C2 particulate combined with γ′-Ni3(Al, Cr) precipitate synergistically reinforced pure Ni matrix composites by reactive hot press techniques. The SEM and XRD results demonstrate that ternary layered Cr2AlC decompose and transform into nonstoichiometric Cr3C2 particles at high temperature, while the additional Al and fractional Cr atoms reacted with Ni matrix to form γ′-Ni3(Al, Cr). Microstructure and mechanical behavior of the as-resulted composite materials in relationship with different fractions of Cr2AlC (10 vol%, 20 vol%, 30 vol% and 40 vol%) are carefully investigated. In 30 vol%Cr2AlC/Ni and 40 vol%Cr2AlC/Ni composites, the in-situ synthesized Cr3C2 particles and γ′ phase are uniformly distributed in the matrix, consequently endowing the composites superior mechanical properties. The flexural strength of 30 vol% and 40 vol% Cr2AlC/Ni composites was 1790 ± 25 MPa and 1752 ± 73 MPa respectively, which is about 7 times higher than the pure Ni matrix. In addition, the tensile strength was determined to be 947 ± 19 MPa and 846 ± 15.9 MPa, respectively. For the substantial reinforcement, the dominant contributions are ascribed to the combined strengthening mechanisms in term of refining the grain, precipitate strengthening and solid-solution strengthening.

Mechanism investigation on high-performance Cu-Cr-Ti alloy via integrated computational materials engineering

In this work, the influence of different Ti additions on microstructure and property in Cu-Cr alloys has been studied and the primary relationship of processing-microstructure-property in Cu-Cr-Ti alloy has been constructed via the CALPHAD-based Integrated Computational Materials Engineering (ICME) approach and experimental validation. The peak-aged Cu-0.5Cr-0.2Ti alloy offers an excellent combination of hardness 192.6 HV, tensile strength 629.3 MPa, yield strength 603.0 MPa, electrical conductivity 51.3 %IACS and elongation 10.9 %. The calculated results suggest that the addition of Ti could promote the nucleation and hinder the growth of Cr precipitate in Cu-Cr-Ti alloys during aging treatment, which may promote the homogeneous formation of small-size precipitate Cr and improve the strength of the Cu-Cr alloy. Microstructural characterization has validated the calculation results and revealed that the exceptional properties of this alloy are mainly attributed to nano-scale Cr precipitates achieved through the optimal thermomechanical processing from present ICME. Thus, the present ICME flowchart is applicable to design alloy composition and optimize the processing for the desired microstructure and property in engineering industries.

Synthesis of Guar Gum Stabilized Nanoscale Zero-valent Iron for Cr (VI) Removal in Water

Guar gum was used in the preparation of a new stabilized nanoscale zero-valent iron (nZVI), as a biodegradation stabilizer. The TEM results showed that the nanoparticles were coated by guar gum, and average particle size was 87.4 nm; XRD results showed that guar gum stabilized nZVI was α-nanoFe0. The batch test results showed that the degradation rate of guar gum stabilized nZVI was 12 times than 200 mesh reduced iron powder. Guar gum could hinder the formation of Fe(III)-Cr(III) precipitate by chelating Fe(III), consequently enhanced the reduction of Cr(VI) to Cr(III).

Investigating defect evolution during thermal treatment in Ni–Cr alloy using positron annihilation spectroscopy

Defects evolved during thermal treatment in high Cr content Ni–Cr alloy have been studied using Positron lifetime and coincidence Doppler broadening spectroscopy complemented with microscopic technique. The single-phase gamma-quenched specimen obtained by solutionization at 1200 °C has been thermally aged at 650 °C and 800 °C. Thermal treatment resulted in the phase transformation of the matrix through precipitation of Cr. It is seen that solutionization treatment followed by quenching resulted in the stabilization of thermal vacancies generated at 1200 °C which effectively trap the positrons. The results infer that these vacancies may form vacancy-Cr complexes which act as nucleation site for Cr aggregation. Positron lifetime and momentum distribution of annihilation electrons indicated that in the aged alloys, positrons are trapped in vacancy-like defects (vacancy clusters/vacancy-solute complex) and the interface between Cr precipitate and matrix, the latter becoming more predominant with subsequent ageing. At the highest ageing studied, vacancy-like defects are evolved within the Cr precipitates. The results indicated that positron trapping sites (vacancies and precipitate interface) are not specific to either Ni or Cr atoms which surround the trapping site in nearly equal proportion. Therefore, unambiguous identification of the defect type at each stage of thermal treatment becomes difficult. Considering positron trapping at the surface of precipitates, we have calculated positron specific trapping coefficient to be ~ 1.33 × 10−6 cm3 s−1, which is of the order estimated for large voids and estimated the number density of precipitates.

Recovery of chromium from vanadium precipitated solution by precipitation with lead salt and leaching with sodium carbonate

The recovery of chromium from vanadium precipitated solution obtained by adding Ca(OH)2 into the chromium-containing vanadate solution and ball milling was investigated by precipitation with lead salt and leaching with sodium carbonate. It has been found that chromium can be effectively enriched by adding PbCO3. The precipitate is the mixture of PbCO3 and PbCrO4∙PbO. The concentration of Cr residue in the solution can be decreased to 16.0 mg/L by adding PbCO3 into vanadium precipitated solution according to Pb/Cr molar ratio 4.0 and adjusting the pH to 12.5 with NaOH stirring for 180 min at 20 °C. Then the precipitates were leached with hot Na2CO3 solution under pH 10.0 at 50 °C to obtain the leach solution containing Na2CrO4 and the leach residue containing PbCO3. After filtration, the leach residue was reused in Cr precipitation and the leach solution was used to circularly leach the Cr precipitate until Na2CrO4 near saturation. Finally, the product of Na2CrO4∙4H2O with purity 99.3% was obtained by evaporation and crystallization of the leach solution.

From coherent to semicoherent—Evolution of precipitation crystallography in an fcc/bcc system

How are crystallographic features developed in phase transformation systems with anisotropic misfits (e.g., bcc/fcc systems)? Comprehensive knowledge about this question is still very limited, which impedes the thorough understanding and the quantitative modeling of microstructure evolution. In this work, we simulated the early stage growth of a Cr precipitate (bcc) in a Cu matrix (fcc) by combining Monte Carlo and molecular dynamics. The simulation results reveal fine details about the evolution of crystallographic features, including the orientation relationship (OR) between the two phases, the precipitate morphology, and the interfacial dislocation structures. The governing event during the evolution process is the generation of a dominant set of dislocations. The selection of the dominant dislocations is rationalized based on minimization of the interfacial energy in the major facet, which contains a single set of dislocations. The initial OR between the coherent precipitate and the matrix is close to the Nishiyama–Wassermann OR. In response to the generation of the dominant dislocations, the OR jumps towards the ideal OR corresponding to the O-line condition, which is close to the Kurdjumov–Sachs OR. This tendency reflects the experimental observations in a Cu-Cr system and provides helpful insight into the actual evolution of crystallographic features.