Evolution Of Phase Composition Research Articles

Evolution of structural-phase state and properties of hypereutectoid steel rails at long-term operation

The methods of modern physical materials science were used to analyze the evolution of microhardness, tribological properties, dislocation substructure and phase composition of the rails with increased wear resistance and contact endurance of DT 400 IR category after missed tonnage of 187 million gross tons on the experimental ring of Russian Railways. It is shown that extremely long-term operation of the rails is accompanied by a decrease (3.1 times) in wear parameter of the rolling surface and an increase (1.4 times) in microhardness, scalar dislocation density (1.5 times) and Fe3C carbide content (1.24 times). Operation of the rails led to a decrease in the crystal lattice parameter, which correlates with an increase in the content of iron carbide. We made the assumptions about physical causes of the change in parameters.

Microstructure and micromechanical properties of magnesium phosphate cement

This paper presents a systematic study on the evolution of phase composition, microstructure and micromechanical properties of magnesium phosphate cement (MPC) and their relations to macroscopic mechanical properties. The results indicate that the microstructure of MPC is mainly composed of a crystal region of potassium magnesium phosphate hexahydrate (MKP) and a hybrid region of magnesium oxide and amorphous hydration products. The elastic modulus and hardness of MKP crystals are 20.18 GPa and 1.15 GPa, respectively. Amorphous hydration products may consist of MgKPO4 and Mg3 (PO4)2. The elastic modulus of amorphous MgKPO4 drops gradually from 51.4 GPa to 29.2 GPa with increasing curing age towards the elastic modulus of crystalline MKP, while the elastic moduli of amorphous Mg3(PO4)2 and unreacted MgO are approximately 160 GPa and 300 GPa, respectively. The macroscopic strength of MPC is mainly dependent on its pore structure rather than the micromechanical properties of hydration products.

Evolution of Phase Transformation on Microwave Dielectric Properties of BaSixO1+2x Ceramics and Their Temperature-Stable LTCC Materials

BaSixO1+2x (1.61 ≤ x ≤ 1.90) and LiF-doped BaSi1.63O4.26 ceramics were prepared by using a traditional solid-state method at the optimal sintering temperatures. The evolution of phase compositions of BaSixO1+2x (1.61 ≤ x ≤ 1.9) ceramics was revealed. The coexistence of Ba5Si8O21 and Ba3Si5O13 phases was obtained in BaSixO1+2x (1.61 ≤ x ≤ 1.67) ceramics. The BaSi2O5 phase appeared inBaSixO1+2x (1.68 ≤ x ≤ 1.90) ceramics. At 1.68 ≤ x ≤ 1.69, only BaSi2O5 and Ba3Si5O13 phases existed. With the further increase in x, the Ba5Si8O21 phase appeared, and BaSi2O5, Ba5Si8O21 and Ba3Si5O13 phases coexisted in BaSixO1+2x (1.70 ≤ x ≤ 1.90) ceramics. The phase compositions of BaSixO1+2x (1.61 ≤ x ≤ 1.90) ceramics were controlled by the ratio of Ba:Si. The BaSixO1+2x (x = 1.68) ceramics with 98.15 wt% Ba3Si5O13 and 1.85 wt% BaSi2O5 phases exhibited a negative τf value (−37.53 ppm/°C), and the good microwave dielectric properties of εr = 7.51, Q × f = 13,038 GHz and τf = +3.95 ppm/°C were obtained for BaSi1.63O4.26 ceramics with 70.05 wt% Ba5Si8O21 and 29.95 wt% Ba3Si5O13 phases. The addition of LiF sintering aids were able to reduce the sintering temperatures of BaSi1.63O4.26 ceramics to 800 °C. The phase composition of BaSi1.63O4.26 ceramics was affected by the sintering temperature, and the coexistence of Ba5Si8O21, Ba2Si3O8, BaSi2O5 and SiO2 phases was achieved in BaSi1.63O4.26-3 wt% LiF ceramics. The BaSi1.63O4.26-3 wt% LiF ceramics sintered at 800 °C exhibited dense microstructures and excellent microwave dielectric properties (εr = 7.10, Q × f = 12,463 GHz and τf = +5.75 ppm/°C), and no chemical reaction occurred between BaSi1.63O4.26-3 wt% LiF ceramics and the Ag electrodes, which indicates their potential for low-temperature co-fired ceramic (LTCC) applications.

Microstructure and properties of Cr–AlSi12 composite coatings pre-coated on Ti–6Al–4V alloy substrate via mechanical alloying and subsequent laser cladding treatment

Cr–AlSi12 composite coating on Ti–6Al–4V alloy substrate was fabricated by mechanical alloying (MA) and subsequent laser cladding (LC). The weight ratio of the mixed powders was Cr: AlSi12 = 60:40. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to investigate the evolution of surface morphologies, cross-section microstructures and phase composition of the coatings before and after laser treatment. The results showed that Al8Cr5, AlCr2, (Si, Al)2Cr and Cr5Si3 were generated in the MA-LC coating through in-situ alloying reaction. The formation of Al3Ti and Ti5Si4 intermetallic compounds was caused by interdiffusion. Metallurgical bonding was achieved at the coating/substrate interface. Results of the scratch test indicated that laser treatment could significantly improve the bonding quality of the interface. Meanwhile, the microhardness of the MA-LC coating was about 3–4 times higher than that of the MA coating. The high-temperature oxidation resistance of the MA-LC Cr–AlSi12 coating was also studied. It was found that after 100 h of oxidation, the MA-LC coating could effectively enhance the oxidation resistance of the substrate. The oxide films and intermetallic phases formed during oxidation process could play a role of intense hindrance to the diffusion of oxygen into the internal Ti–6Al–4V substrate. The oxidation mechanism of the coating is discussed in detail.

Synthesis, Crystal Structure and Photoluminescent Properties of Red-Emitting CaAl4O7:Cr3+ Nanocrystalline Phosphor

Calcium dialuminate, CaAl4O7, nanopowders with a grossite-type structure, doped with chromium ions, were synthesized via the combined sol–gel solution combustion method. The evolution of phase composition, crystal structure, and microstructural parameters of the nanocrystalline materials depending on the temperature of the thermal treatment was investigated via X-ray powder diffraction and applying the Rietveld refinement technique. The photoluminescent properties of CaAl4O7 nanophosphors activated with Cr3+ ions were studied over the temperature range of 4.5–325 K. The samples show deep red and near-infrared luminescence due to the 2E → 4A2 and 4T2 → 4A2 energy level transitions of Cr3+ ions under excitation in the two broad emission bands in the visible spectral region. The R lines emission reveals a strong temperature dependence. The feasibility of the material for non-contact luminescence sensing is investigated, and good sensitivity is obtained based on the (R2/R1) luminescence intensity ratio and the lifetime of the emission.

Deterioration Process of Cementitious Material Properties under Internal Sulphate Attack

As one of the important factors affecting the structural durability of cementitious materials, sulphate erosion not only reduces the service life of the material but also poses a threat to the structural safety of the project. At present, scholars around the world have conducted extensive research on topics related to external sulphate attacks and have achieved fruitful results. However, the process and mechanism of attack degradation of the gelling material are not clear. In this paper, gypsum sand was introduced into the mortar. The effects of gypsum content, gypsum particle size and curing temperature on physical properties such as expansion and strength of specimens were investigated. X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), Scanning Electron Microscopy (SEM) and energy dispersive spectrometry (EDS) were used to analyse specimens’ phase composition and microstructure evolution at different attack ages. Finally, cementitious materials’ degradation process and mechanism under internal sulphate attack (ISA) were analysed. Through the above research, the following main conclusions are drawn: (1) The swelling rate of cement mortar specimens all increased with the increase of gypsum dosing; (2) The expansion of cement pastes and mortars does not increase with the increase in curing temperature; (3) The gypsum particle sizes are smaller, the expansion of mortar specimens is larger, and the loss of compressive and bending strength of mortar specimens is large; and (4) The main reaction product of ISA is Ettringite (AFt). The gypsum formed during the ISA process does not cause expansion, while AFt is the main reason for the destruction of the cementitious material.

Influence of mono-carbonate hydrates on mechanical properties of CAC bonded castables fired at 800 °C

The increase of intermediate-temperature strength of CAC bonded castables is significant for the spalling resistance. In this work, micro-sized calcium carbonate (MCC) powders were introduced into calcium aluminate cement (CAC)-bonded castables to form a novel calcium aluminate mono-carbonate hydrate C4AC‾H11 (3CaO·Al2O3·CaCO3·11H2O) rather than common hydrates C3AH6 (3CaO·Al2O3·6H2O) and C2AHx (2CaO·Al2O3·xH2O). The phase and microstructure evolution of C4AC‾H11 and the effect of C4AC‾H11 formation on the mechanical properties of corundum-based castables after heating at 800 °C has been studied. The phase composition and microstructure evolution of castables were characterized via utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) as well as differential scanning calorimetry (DSC). The results indicated that the introducing of MCC could dramatically improve the intermediate-temperature strength of the low and ultra-low CAC bonded castables owing to the preserved cross-linked lamellar microstructure after the dehydration and decomposition of the lamellar C4AC‾H11 precursors fired at 800 °C.

Low‐Temperature Solidifiable Liquid Metal with Ultrahigh Thermal Conductivity Enabled by Spontaneous Phase Transition for Electronics’ Safety and Long‐Life Cooling

Gallium‐based liquid metals have displayed many advantages as a thermal interface material for high‐power electronic devices. However, due to their excellent rheological property, liquid metals do carry risks for electronic systems, including the possibility of short circuit or even failure. For this problem, a low‐temperature solidifiable liquid‐metal EGaInSn/Cu composite is proposed, and the matter state of this composite can transform from liquid to solid spontaneously even at room temperature. Subsequently, the liquid–solid transition behavior and phase composition evolution of liquid‐metal composites during solidification are investigated, and it is found that the solidifying reaction is triggered by the formation of CuGa2 intermetallic compounds and the precipitation of In3Sn solid solutions. Moreover, this study confirms that the obtained composite with only a 36% volume ratio of copper fillers can achieve an ultrahigh thermal conductivity of 86.7 W (m K)−1, which is far greater than that of other analogous liquid‐metal composites. More importantly, the mechanical and thermal properties of this material after solidification have always maintained steady in the thermal cycling test. It demonstrates that the low‐temperature solidifiable liquid metal can satisfy the needs of electronics’ safety and long‐life cooling application.

Phase engineering of Cu@Cu2O core-shell nanospheres for boosting tandem electrochemical CO2 reduction to C2+ products

Cu-based CO2 electrochemical reduction (CO2ER) is promising for reducing greenhouse gas emission and producing high-value multicarbon (C2+) chemicals and fuels. Unfortunately, the C2+ selectivity is still quite low. In this work, well-defined Cu@Cu2O core–shell nanospheres with time-dependent evolution of phase composition, crystallinity and morphology were specifically designed by a facile chemically induced self-transformation strategy. A maximum C2+ Faradaic efficiency (FE) exceeding 79%, including FEC2H4 reaching 44%, was achieved using phase-engineered Cu@Cu2O nanospheres. Based on the temperature-programmed desorption analyses and in-situ Raman spectroscopy, the adsorption behaviors of both CO2 reactant and *CO intermediate can be synergistically tuned by phase engineering of Cu@Cu2O nanospheres: Cu2O shell enhances *CO2 and *CO adsorption coverage, while porous Cu core concentrate and strengthens *CO intermediates for subsequent CO-CO coupling towards C2+ products. This work will shed new light on the phase engineering of Cu-based tandem electrocatalysts for tuning CO2/CO-catalyst interaction and modulating CO2ER processes and selectivity.

Effect of boron on the microstructural evolution and wear resistance of high-hardness Fe-based alloy coatings prepared by laser cladding

One of the primary failure modes of 45 steel is severe surface wear, which significantly raises its application cost. In order to improve the wear resistance, high-hardness Fe-based alloy coatings with varying boron contents were prepared on 45 steel substrates by preplaced-powder laser cladding in this study. The effect of boron content on the phase composition and microstructural evolution of the coatings were systematically studied. The proportion, morphology, and distribution characteristics of boride phases in the coatings were discussed in detail. The results demonstrated that the Fe-based alloy coatings with different boron contents were composed of α-Fe, Cr7C3, and Fe2B phases. The boron content had a significant influence on the morphology and proportion of the boride phases. With the increase of boron content, the proportion of boride phases gradually increased and the morphology transition was reticular → cluster-shape → long strip-shape → plate-shape. The composition analysis revealed that the boride was Cr-rich Fe2B phase and the content of Cr in the borides increased with the boron content of the coating. The addition of boron could effectively improve the hardness and wear resistance of the Fe-based coatings, which could be attributed to the boride hard phases in the microstructures. The coating with 6.0 wt% B exhibited the highest microhardness and least amount of wear loss. The wear mechanism of the coating with different boron contents was also discussed.

Influence of stabilizers on hydrothermal behavior of zirconia coatings by APS

In recent years, the degradation of zirconia in a humid environment has attracted the attention of researching. In this work, Mg0.09Zr0.91O1.91 (MSZ), Y0.09Zr0.91O1.955 (YSZ) and Ce0.09Zr0.91O2 (CSZ) powders were prepared by co-precipitation method, the corresponding zirconia coatings were fabricated by atmospheric plasma spraying (APS). All coating samples were subjected to hydrothermal treatment to investigate their degradation process in moisture. The evolution of phase composition and microstructure were characterized. Results show that the content of monoclinic phase (m) in MSZ, YSZ and CSZ coating samples increased after hydrothermal treatment, rising by 47 % in MSZ coating, by 31 % in YSZ coating and by 8 % in CSZ coating. The degradation of internal structure of coatings was more serious with the prolongation of hydrothermal treatment time. This is because different stabilizers will cause different oxygen vacancy concentration in the zirconia unit cell, which determines the hydrothermal stability of zirconia. Under the tested condition, CSZ has the lower oxygen vacancy concentration (4 %) than MSZ (11 %) and YSZ (7 %), exhibiting better hydrothermal stability.

Evolution of morphology, microstructure and phase composition of zirconia thin coating on copper as a result of low energy high current pulsed electron beam irradiation

Using X-ray diffraction, scanning and transmission electron microscopy we studied the evolution of the morphology, microstructure and phase composition in the near-surface layer of copper covered with thin (2.8 μm) ZrO2 coating induced by low-energy high-current pulsed electron beam irradiation (the surface energy density was in the interval of 5.0–18.0 J/cm2, the accelerating voltage was 30 kV, the pulse duration was 3.2 μs, the number of pulses was 10). The variation of adhesion of the coating to substrate was evaluated using scratch testing. The evaporation of the upper part of the coating during irradiation was found and the thickness of the coating nonlinearly decreased with the increase of the energy density. We discussed the reasons for the surface cracking taking into account microstructural changes in the near-surface layer of the material. The irradiation was found to transfer most of monoclinic ZrO2 phase in the as-deposited coating to tetragonal and, possibly, cubic one. The factors influencing the adhesive strength of the coating were revealed and a potential for the increase of adhesion was demonstrated. We showed that irradiation with enhanced surface energy density was required to obtain copper-based composite hardened with zirconia nanoparticles in the near-surface layer. The thickness of the composite layer may be as much as 6 μm.

Optimization design of environmental-friendly Cu-Fe laser cladding coating for self-grown microchannel in a marine corrosive environment

Marine biofouling is a critical issue that seriously deteriorates the service performance of marine infrastructure. It is a big challenge to develop environmental-friendly materials for long-term marine antifouling. Herein, we have proposed the utilization of high-speed laser cladding technology to fabricate copper-iron alloy capable of self-grown microchannel through dealloying process in a marine corrosive environment, which could effectively store copper ions. The phase composition and microstructure evolution were characterized and analyzed by scanning electron microscopy. Corrosion mechanism of dealloying and distribution of microchannel was investigated. After being immersed for 2 months, the samples can form a de-ironized microchannel layer with a thickness of 350 µm, which reduces the bonding strength between corrosion products and the surface, thereby promoting the flacking of the corrosion products. The self-grown microchannel could store the copper ions which will solve the problem that the antifouling effect of traditional copper alloys decreases during long-term seawater immersion. These results may guide the advanced design of new promising antifouling materials with environmental-friendly, durable, and remarkable antifouling capability for different practical requirements in marine engineering.

Effects of the La2O3 addition contents on the ablation performance of in-situ La-doped ZrC-SiC-ZrSi2 coating for C/C-ZrC-SiC composites

The C/C-ZrC-SiC composites coated by the La-doped ZrC-SiC-ZrSi2 coatings containing different La contents were fabricated by reactive melt infiltration (RMI) combined with gradient pack cementation in a one-step process. The composites' ablation behaviors under the oxyacetylene flame were comparatively studied. The effects of the La2O3 addition contents on the microstructure and phase composition evolution on the surface of the composites caused by ablation were investigated. The results indicated that the C/C-ZrC-SiC composites with an in-situ La-doped ZrC-SiC-ZrSi2 coating prepared by the mixed powders with 15 wt% La2O3 (15LZS) showed a better ablation performance. After ablation for 120 s, their mass and linear ablation rates were − 0.62 ± 0.15 mg/s and − 2.42 ± 0.24 μm/s, respectively. Such good ablation resistance should owe to appropriate La contents on the surface of the 15LZS. During ablation, the La elements could promote the formation of a dense oxide layer, which was composed of the m-ZrO2, t-ZrO2, and Zr0.9La0.1O1.95 phases. It could efficiently inhibit oxygen diffusion and endure the mechanical denudation of the oxyacetylene flame.

Preparation of magnesium and zinc aluminate spinels by microwave heating: Influence of the oxide precursors on the phase composition

This study focuses on understanding the difference between conventional and microwave (MW) heating to obtain magnesium and zinc aluminate spinels (MgAl 2 O 4 and ZnAl 2 O 4 ) starting from raw oxide powders (magnesia/alpha-alumina, magnesia/gamma-alumina and zincite/alpha-alumina mixtures). The samples were prepared from these different oxide precursors and submitted to different thermal cycles in a MW multimode cavity. The evolution of phase composition was studied by X-Ray Diffraction (XRD) analysis. The choice of the precursors aimed at studying the influence of the difference of dielectric properties and of the specific surface area on the phase formation under MW. It was shown that spinel phases could be obtained by rapid MW thermal cycles ( i.e. , 100 °C/min under MW vs 25 °C/min under conventional heating). The presence of ZnO as a MW absorbent was beneficial for the MW/material interactions. But, for the three considered mixtures, a SiC susceptor was necessary to facilitate heating.

Effect of annealing on the structure and phase composition of Cu-Al composite produced by conventional and accumulative HPT

The paper presents the first results of the investigation of the effect of annealing on the evolution of microstructure and phase composition of a Cu-Al composite obtained by accumulative high pressure torsion (HPT). Cu-Al composites produced under 6 GPa in 10 revolutions at room temperature with conventional and accumulative HPT were annealed at 450°C for 15 min. Electron microscopy and energy dispersive spectrometry analysis showed that annealing enhances the solid-state reaction. In the sample after conventional HPT and post-deformation annealing, grayer contrast layers containing intermetallic compounds were formed at the copper-aluminum interface. The contrast on the microstructure images of the sample after accumulative HPT and post-deformation annealing is more uniform than after conventional HPT and annealing. In the sample, a more intense phase transformation occurred. This led to a noticeable increase in the volume fraction of the intermetallic compounds up to 5 – 6 times. X-ray diffraction analysis indicates that in the annealed sample after accumulative HPT, alongside with initial copper, there is also a solid solution of aluminum in copper, which differs from copper with a crystal lattice parameter. Post-deformation annealing led to the formation of different quantity of intermetallic compounds in the studied samples.

Phase evolution and microstructure of SiC–MgAl2O4–Al composites sintered in argon atmosphere at 1450 °C: Reactions in Al–O–C system

SiC–MgAl2O4–Al composites were prepared using SiC, MgAl2O4, corundum and Al powder as raw materials by firing at 1450 °C in flowing argon. The effects of binders on phase composition and microstructure evolution were investigated. The results show that the external of specimens with thermosetting phenolic resin and water soluble resin as binders both contained SiC, MgAl2O4, corundum and Al4O4C phases. In center of the specimens, Al4C3 and Al2OC phases appeared in the thermosetting phenolic resin bonded specimens while Al4O4C and Al2OC phases appeared in the water soluble resin bonded specimens. The microstructure shows that MgAl2O4 whiskers generated at surface of both specimens through gas-gas reaction. As for the specimens with thermosetting phenolic resin as binder, the residual carbon (decomposed from phenolic resin) and Al in the external of the specimen react with O2 to form CO and Al2O, which promoting the formation of plate-like Al4O4C. In the center of the specimen, Al4C3, Al2O3 and Mg(g) formed. Mg(g) migrates to outside and transforms to MgAl2O4 whiskers, and a part of Al4C3 transform to columnar Al2OC. Al2OC whiskers can also be generated through the reaction among Al2O, CO and C. Compared with the thermosetting phenolic resin bonded specimens, Al at external of the water soluble resin bonded specimen reacts with O2 to form Al2O3, which further transforms to particle Al4O4C. In the center of water soluble resin bonded specimen, a little Al4C3 formed and can totally transform to Al4O4C and Al2OC.

Transparent diamond ceramics from diamond powder

Diamond possesses a unique combination of excellent optical, thermal, and mechanical properties, and is therefore an ideal transparent ceramic material for harsh and extreme environments. Due to its important applications in technology, transparent diamond ceramic (TDC) has been explored and prepared by chemical vapor deposition (CVD) or direct conversions of non-diamond carbon precursors at high pressure and high temperature (HPHT), but the preparation of large-size TDC with high mechanical strength remains a challenge. Here, we report for the first time, a transparent polycrystalline diamond ceramic from diamond powder with a transmittance of ∼60 % at wavelengths of 400–1600 nm. The analyses of phase composition, residual stress and microstructure evolution of the sintered samples with different sintering conditions indicate that compression at high temperatures (>2000 ⁰C) facilitates the deformation of diamond grains, allowing for densification and diamond-diamond bonding formation. The sintering pressure of the diamond powders with an optimized particle size distribution was dramatically reduced from 16 GPa to 10 GPa. Our results, based on successfully preparing centimeter-sized TDC, set the standard and the precedent for the large-scale preparation of larger TDC in proximity to industrial conditions.

Microstructure Evolution of AZ91 Magnesium Alloy Welded Joint under Magnetic Field and NiCl2 Activated Flux

As the lightest engineering materials, magnesium alloys have been widely used. Because of the specific chemical and physical characteristics, the weldability of magnesium alloy is poor. Adopting suitable welding technology and improving the quality of magnesium alloy welded joints is key to their successful application. According to previous research data, it was found that the combined action of magnetic field and activated flux has a positive effect on improving-welding efficiency and improving the properties of a welded joint, butanalysis of microstructure evolution is insufficient. In this paper, AZ91 magnesium alloy was welded by TIG welding with activated flux and external longitudinal AC magnetic field. The phase composition and microstructure evolution were investigated. The experimental results revealed that the phase composition of welded joint was not changed due to the introduction of the magnetic field and activated flux, the growth patterns of grain in the weld seam and heat-affected zone were different. When the activated flux amount was 3 mg/cm2 with the effect of the magnetic field, the grain size of the weld seam was the finest, which was 18.96 μm. However, the grain size of the weld seam was larger than that of base metal. The crystallographic characteristics of grain boundaries in the weld seam and base metal were both LAGBs. The microstructure of the weld seam was messier than the base metal due to the larger misorientation angle. Under the combined action of the magnetic field and activated flux, the crystallization nucleation condition of the molten pool was changed, the formation of twins was promoted, and the crystal could selectively grow parallel with the (0001) basal plane.

Influence of Degree of Severe Plastic Deformation on Thermal Stability of an HfNbTiZr Multi-Principal Element Alloy Processed by High-Pressure Torsion.

Severe plastic deformation (SPD) is an effective route for the nanocrystallization of multi-principal element alloys (MPEAs). The stability of the refined microstructure is important, considering the high temperature applications of these materials. In the present study, the effect of SPD on the stability of a body-centered cubic (bcc) HfNbTiZr MPEA was investigated. SPD was performed using a high-pressure torsion (HPT) technique by varying the number of turns between ½ and 10. The evolution of phase composition and microstructure was studied near the disk centers and edges where the imposed strain values were the lowest and highest, respectively. Thus, the shear strain caused by HPT varies between 3 (½ turn, near the center) and 340 (10 turns, near the edge). It was found that during annealing up to 1000 K, the bcc HfNbTiZr alloy decomposed into two bcc phases with different lattice constants at 740 K. In addition, at high strains a hexagonal close packed (hcp) phase was formed above 890 K. An inhomogeneous elemental distribution was developed at temperatures higher than 890 K due to the phase decomposition. The scale of the chemical heterogeneities decreased from about 10 µm to 30 nm where the shear strain increased from 3 to 340, which is similar to the magnitude of grain refinement. Anneal-induced hardening was observed in the MPEA after HPT for both low and high strains at 740 K, i.e., the hardness of the HPT-processed samples increased due to heat treatment. At low strain, the hardness remained practically unchanged between 740 and 1000 K, while for the alloy receiving high strains there was a softening in this temperature range.