Bcc Phase Research Articles

Field-assisted sintering of high-entropy alloy-reinforced aluminium matrix composites: phase identification and microstructural properties

This study investigates the design, phase identification, and microstructural properties of high-entropy alloy (HEA)-reinforced aluminium (Al) matrix composites. Thermophysical expressions for HEAs were employed during the design phase of the HEA; both theoretical frameworks and experimental analyses were used to anticipate stable phases while a field-assisted sintering technique was employed to consolidate the samples. Calculation of phase diagram (CALPHAD) predictions for the phases present in the HEA align with valence electron concentration (VEC) calculations as both predicted the presence of BCC and FCC phases. The microhardness results reveal a substantial increase in the hardness value of the composites as compared to the pure Al, such that as low as 5 wt% HEA addition resulted in over a 100% improvement, while the densification of the composites was found to decrease with an increase in the wt% of HEA. SEM micrographs and XRD analyses show fair dispersion, bonding, and phase integration in the HEA-reinforced composites.

Surface aspects of novel Bio-HEAs MAO-treated in a Ca-, P-, and Mg-rich electrolyte

This study evaluated the effect of alloying elements, applied voltage, and bioactive species (Ca, P, and Mg) enrichment during the micro-arc oxidation (MAO) treatment of novel high entropy alloys (HEAs) targeted for biomedical applications. The non-equiatomic TiZrNbTaMo (TaMo), TiZrNbTaMn (TaMn), and TiZrNbFeMo (FeMo) samples were submitted to MAO treatment at distinct voltages (100, 200, and 300 V), then their chemical, phase, and morphological aspects were evaluated by x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM). Finally, the preliminary physicochemical behavior regarding contact angle and surface energy in distilled water at room temperature was evaluated. The results indicated that the alloying elements played a global role in the bulk’s phase composition, possessing distinct proportions of BCC and HCP phases. The MAO-treated surfaces depicted different mechanisms of anodic oxide growth and dielectric breakdown, forming the typical porous surface at distinct applied voltages. The bioactive species (Ca, P, and Mg) were gradually enriched in the oxide layer, composed of distinct nano-crystalline and amorphous layers that are typical of MAO-treated surfaces. As a result, roughness, contact angle and surface energy values of the MAO-treated samples were affected by the applied voltage and the bulk’s chemical composition, indicating potential for use in the biomedical field, especially as long-term implants and bone fixation devices.

Microstructural study on in-situ high-entropy (NbMoTaWV)C reinforced nanocrystalline NbMoTaWVC refractory high entropy alloys prepared by mechanically alloying

Refractory high-entropy alloys (RHEAs) can be commonly regarded as the best candidates for potentially substituting for the nickel-based superalloys practically used in the areas of aviation and nuclear industry, which can significantly endure in high-temperature and harsh environment. In this work, a nanocrystalline NbMoTaWVC RHEA is successfully produced by mechanical alloying method and X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spherical aberration corrected transmission electron microscopy (AC-TEM) are employed to systematically characterized the microstructural details of NbMoTaWV and NbMoTaWVC RHEAs mechanically alloyed powders. Our results can support the evidence that the observable minimum nanoparticle sizes of the NbMoTaWV and NbMoTaWVC RHEAs considerably decrease to approximately ∼100 nm. Furthermore, the average grain sizes are gradually refined and thus notably drop to around of 30–50 nm, and five elemental powders can be found to be homogeneously alloyed. The evidence can be confirmed that the order of solid solution may be proposed as follows: Nb → Mo → V → Ta → W. The chemical short-range order occurred at the local nanoscale of NbMoTaWV and NbMoTaWVC RHEAs. Meanwhile, further microstrutural analysis can demonstrate that NbMoTaWV and NbMoTaWVC RHEAs powders with ultrafined grain have a bcc phase structure and bcc + bct matrix phases combined with high-entropy tungsten carbides (NbMoTaWV)C and (NbMoTaWV)2C of nano-precipitated phases, respectively, suggesting that the martensitic transformation probably occurred. The NbMoTaWV and NbMoTaWVC RHEAs powders of locally crystal lattice distortion rates reached approximately 8.07% and 6.33%.

High-temperature tribological properties of a novel AlFeCoNiCr–Cr3C2 cermet coatings

Microstructural instability of NiCr–Cr3C2 coating greatly limits its high-temperature tribological applications. In this work, we present a design concept for NiCr alloys based on an enthalpy-guided approach. A novel AlFeCoNiCr–Cr3C2 coating was fabricated using a supersonic plasma spraying followed by annealing. The high-temperature tribological results suggested that, due to the precipitation strengthening of Cr23C6 nano-grains in the interfacial transitions and the high plasticity of the disordered BCC (A2) and FCC (A1) phases in the AlFeCoNiCr alloy, the wear rate of the coating after annealing at 600 °C decreased by 47.6 % compared to the NiCr–Cr3C2 coating. The high density of mesoscopic defects further contributed to the strengthening and plasticity of the coating. After annealing at 900 °C, a net-shaped agglomeration of Cr23C6 and A2 phases accelerated oxidation diffusion and abrasive wear, leading to an increase of wear rate of coating. The produced wear debris mainly came from NiCr2O4, Cr2O3, NiO, Al2O3 and Fe2O3, where the NiCr2O4 was the product from the reaction between the Cr2O3 and NiO phases.

Effect of Al content on the corrosion behavior and mechanism of AlxCoCrFeNi high-entropy alloys

Al addition is known to improve the tensile strength and high-temperature oxidation behavior of the AlxCoCrFeNi high-entropy alloy (HEA). However, the corrosion behavior and mechanisms associated with these HEAs remain unclear. The corrosion resistance of structural materials is as important as their mechanical properties. In this study, AlxCoCrFeNi HEAs with different molar ratios of Al (x = 0.0, 0.5, 1.0, and 1.5) and various crystal structures (FCC, FCC + BCC, and BCC phases) were prepared, and their corrosion behavior and mechanisms were studied, which revealed a competitive relationship between the Al and Cr passivation films. The thickness of the Al passivation film increased with increasing Al content, which was found to be the main reason for the decrease in the corrosion resistance of the AlxCoCrFeNi HEAs. The corrosion type of the AlxCoCrFeNi HEA changed from pitting corrosion to selective corrosion with increasing Al content, and the corroded elements changed from (Co, Cr, Fe, and Ni) to (Al and Ni) and then (Al, Ni, and Co). Accordingly, the corrosion mechanisms associated with the AlxCoCrFeNi HEAs were elucidated.

Non-precious metal high-entropy electrocatalysts (Al0.5NiCoCr-X0.5) for OER application

The high entropy alloy electrocatalysts demonstrate exceptional efficiency in the production of hydrogen through water electrolysis. Consequently, the development of durable and economically efficient electrocatalysts has become an urgent objective to accomplish. In order to achieve this goal, a bulk non-precious metal high-entropy alloy, Al0.5NiCoCr-X0.5 (Mo, Mn, Cu, V, Fe), was synthesized and characterized in this study through physical phase analysis and electrochemical property test. To explore the reasons for the influence of the five added elements on the catalytic performance of high entropy alloys in this system and to find the OER electrocatalyst with the best catalytic performance. Electrochemical performance tests were performed in 1 M KOH electrolyte. At a current density of 10 mA·cm−2, the overpotential of the high-entropy alloy catalyst Al0.5NiCoCrMo0.5 was lower than that of the high-entropy alloy with the addition of the other four elements respectively, which was only 327 mV, and lower than that of the conventional noble metal catalyst RuO2, which had an overpotential of 342 mV. This is attributed to the addition of Mo element, which makes Al0.5NiCoCr produce a large number of HCP phases on top of the original FCC phase and a very small number of BCC phases, which is more conducive to the generation of active sites on the surface of the catalysts, and thus improves the OER activity, and the stability can be maintained for at least 20 hours. Therefore, Al0.5NiCoCrMo0.5 high-entropy alloy catalysts can be used in industrial hydrogen production instead of the traditional precious metal catalysts, and it has a rather broad application prospect, and at the same time, it lays a solid foundation for the application of transition metals in catalysts.

Diffusion coefficients and atomic mobilities in the BCC phase of the Al–Nb–V system

Diffusion coefficients in the BCC phase of the Al–Nb–V ternary system are studied for the first time, including an assessment of the atomic mobilities. Ternary interdiffusion coefficients are obtained from the intersecting diffusion paths of several sets of diffusion couples that are annealed at both 1100 °C and 1200 °C. Existing experimental data from the pertinent binary systems are also employed for the assessments of atomic mobilities using the 1-parameter Z-Z-Z binary diffusion coefficient model developed by Zhong et al [1]. Interdiffusion coefficients in the BCC region of the Al–V system are also extracted through a forward-simulation analysis and incorporated into the mobility modeling. A complete description of diffusion in the BCC phase of the Al–Nb–V system is presented following the Binary and Cross-Binary Parameters Only (BCBPO) model developed by Zhong and Zhao [2]. Our data will be valuable input to diffusion-related simulation of refractory high entropy alloys containing aluminum.

Development of TiNbMoMnFe multi-principal element alloy coating using mechanical alloying and HVOF thermal spray

Multi-Principal Element Alloys (MPEA) were designed to possess good strength, ductility, wear and corrosion resistance, and biomedical compatibility. There are many applications where failure is associated with surface-related degradation, and suitable coatings can mitigate them. This study focuses on the development of MPEA coatings using the HVOF thermal spray process and explores their mechanical and tribological responses. In the present study, the transitional and refractory elements-based feedstocks were prepared by a mechanical alloying process using a high-energy ball mill for 5 h, 10 h, and 15 h milling time. The molar ratio of the developed coating was TiNbMoMnFeOX (1:1:1:1:1:X, where X = 0.48 to 0.62). Thus, prepared feedstock powders and coatings were characterized to record their metallurgical, mechanical, and tribological responses wherever it is applicable. The used scientific tools include X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), universal tribometer, and nanoindenter set-up. The results showed that mechanical alloying led to the formation of MPEA, and the 15 h milled MPEA powder coating expressed superior performance. Furthermore, the process exhibited significant microstructural changes in the alloy system, and dual (TiNb and TiMo) and ternary (TiNbMo) BCC phases were developed during the process. These BCC phases were responsible for the coating's improved mechanical and tribological responses. The solid solution hardening of the ternary phase (TiNbMo) was the most dominant mechanism for improving the mechanical and tribological properties.

Corrosion behaviors and mechanism of AlxCrFeMnCu high-entropy alloys in a 3.5 wt% NaCl solution

This study investigated the corrosion behavior of as-cast AlxCrFeMnCu (x = 0, 0.5, 1.0, 1.5, 2.0) high-entropy alloys (HEAs) in a 3.5 wt% NaCl solution at room temperature. The results indicated that the corrosion resistance of the AlxCrFeMnCu HEAs decreased with increasing Al content. Intergranular corrosion was the primary corrosion type for CrFeMnCu and Al0.5CrFeMnCu HEAs, while Al1.0CrFeMnCu, Al1.5CrFeMnCu, and Al2.0CrFeMnCu HEAs exhibited selective corrosion with enrichment of Al and Cu in the BCC2 phase. The XPS fitting calculations indicated that an increase in the molar ratio of Al led to a decrease in Cr2O3 content and an increase in Al2O3 content, which weakened the stability and protective properties of the passive film.

Revealing the mechanical behavior of Ti48-xZrxHf26Nb26 high-entropy alloy through zirconium content variations

Refractory high-entropy alloys (RHEAs) composed of Ti, Zr, Hf, and Nb have emerged as promising materials for high-temperature aerospace applications due to their exceptional balance of strength and toughness, coupled with a reduced density and softening resistance. This study delves into the influence of alloy composition on the mechanical properties, a pivotal aspect in the design of RHEAs. We investigate a series of Ti48-xZrxHf26Nb26 (x = 14, 18, 22, 26, 30, 34) alloys, prepared through suction casting and homogenization treatments. The phases, microstructure, and fracture morphology of these alloys are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD), subsequent tensile tests provide insights into the strength and elongation characteristics of alloys. The homogenized alloys consistently exhibit one BCC phase with equiaxed grains, whereas the fracture mode shifts from intergranular to transgranular, and return to intergranular as the Zr content increases. Experimental results reveal an asymmetry mechanical behavior, alloys with higher Ti content display superior toughness (elongation 17.83 % for Ti = 34 at%) compared to those with higher Zr content (elongation 16.05 % for Zr = 34 at%). Among them, the Ti22Zr26Hf26Nb26 alloy achieves the peak tensile strength of 695.25 MPa, indicating an inverse relationship between strength and toughness. Solid-solution strengthening and chemical short-range orderings emerge as the predominant contributors to the overall strength of the TiZrHfNb alloys. To gain a deeper understanding of the mechanical behavior at the atomic scale, we performed first-principles calculations to investigate the elastic properties and charge density of Ti48-xZrxHf26Nb26 alloys in the BCC structure. These calculations shed light on the underlying mechanisms governing the strength and toughness behavior. The present work offers valuable insights into the design of mechanical properties of TiZrHfNb RHEAs, serving as a paradigm for future materials development in this field.

Diffusivities and Atomic Mobilities in BCC Ti-Fe-Cr Alloys.

In this research, the diffusion behaviors within the Ti-Fe-Cr ternary system were examined at the temperatures of 1273 K and 1373 K through the diffusion couple technique. This study led to the determination of both ternary inter-diffusion and impurity diffusion coefficients in the body-centered cubic (bcc) phase for the Ti-Fe-Cr alloy, utilizing the Whittle-Green and Hall methods. The statistics show that the average diffusion coefficients D˜FeFeTi and D˜CrCrTi measured at 1273 K were 1.34 × 10-12 and 3.66 × 10-13, respectively. At 1373 K, the average values of D˜FeFeTi and D˜CrCrTi were 4.89 × 10-12 and 1.43 × 10-12. By adopting the CALPHAD method, a self-consistent database for atomic mobility in the bcc phase of the Ti-Fe-Cr system was established. This database underwent refinement by comparing the newly acquired diffusion coefficients with data from the existing literature. Diffusion simulations for the diffusion couples were performed, drawing on the established database. The error between the simulated diffusion coefficient and the experimental measurement data is within 15%, and the simulated data of the component distance distribution and diffusion path are in good agreement with the experimental data. The simulations generated results that aligned well with the observed experimental diffusion characteristics, thereby affirming the reliability and accuracy of the database.

Study on hydrogen storage properties of Ti–V–Fe–Mn alloys by modifying Ti/V ratio

The high stability of hydride phase has limited the improvement for the hydrogen storage properties of Ti–V based alloy at room temperatures. In this work, the stability of hydride was reduced by designing a low-price Ti–V–Fe–Mn alloy, and the effect of Ti/V ratio on the crystal structure and hydrogen storage properties was systematically investigated. The Ti40-xV40+xFe15Mn5 (x = 0, 2, 4, 6, 8) alloys were synthesized using arc melting, and the as-prepared alloys are all composed of single BCC phase. The lattice constant and cell volume decrease linearly with a lessening in Ti/V ratio. The reduction of cell volume makes it difficult for hydrogen atoms to diffuse, resulting in a sluggish hydrogen absorption rate. The dehydrogenation plateau in PCI curve rises and corresponding thermodynamics is optimized with a decrease in the lattice constant, and the hydrogen atoms are more readily to release, especially for Ti32V48Fe15Mn5 alloy with the dehydrogenation capacity of 1.83 wt% at 373 K. The result indicates the thermodynamic properties can be optimized by adjusting the lattice constant of Ti–V–Fe–Mn alloys, and hydrogen storage capacity is improved effectively. This study provides a reference for composition design of Ti–V–Fe–Mn alloys for high-density hydrogen storage.

Effect of quenching temperature on the microstructure evolutions and strength-ductility of W-Ni-Cu alloy at room-temperature and cryogenic

Tungsten (BCC phase) exhibits distinct ductile-to-brittle transition characteristics. As temperature decreases, brittleness increases, ductility decreases, significantly limits its engineering applications. Here, W-5Ni-2Cu alloy was prepared by powder metallurgy, and the effect of different quenching temperatures on its microstructure evolution and mechanical properties at room-temperature and cryogenic. According to the results, rapid quenching can significantly improve the strength-ductile of W-5Ni-2Cu, especially the cryogenic properties. After quenching at 1200 °C, the strength-ductility of W-5Ni-2Cu from room temperature to −43 °C did not deteriorate, and compared with the sintered alloy, the tensile strength and elongation were increased by 7.3% and 13.0% at room-temperature, and by 16.0% and 100.0% at cryogenic. The appropriate quenching temperature can effectively refine the W grain size, reducing the WW continuity and dihedral angle, while the quenching temperatures reaches 1300 °C, it will cause abnormal W grain growth and deteriorate the mechanical properties. Furthermore, rapid quenching changes the fracture mode from intergranular fractures to transgranular fractures. Especially, the W- 〈111〉∥γ-〈110〉 preferential orientation relationship is obviously improved at −43 °C, increasing the interfacial bonding strength and co-deformation ability of W-γ phase, thereby slowing down the hardening rate and increasing the strength and elongation.

Comparison of microstructure, damping capacity, and mechanical properties of cast and deformation processed Fe17Mn alloys

There were few works on cast FeMn damping alloys although many studies have been conducted on deformation processed (DP) counterparts. In this study, we investigated the differences in damping and mechanical properties of as-cast and as-DP Fe17Mn alloys and the effect of solution treatment at 1050℃ (ST) on their properties. The as-cast Fe17Mn alloy demonstrated a higher damping capacity but lower strength than the as-DP Fe17Mn counterpart. As much as 18 % of the BCC phase was distributed as dendrite in the Mn-depleted region of the as-cast Fe17Mn alloy. The DP Fe17Mn alloy inherited some BCC phase with less than 1 % content formed during the casting. The ST further improved the damping capacity and plasticity but decreased the strength in both the cast and DP Fe17Mn alloys. After the ST, the cast Fe17Mn alloy also showed good mechanical properties, with tensile strength up to 645 MPa and fracture up to 40 %. Our results shed light on the potential application of cast Fe17Mn alloy in mechanical components.

The role of the preparation route on microstructure and mechanical properties of AlCoCrFeNi high entropy alloy

Nearly equiatomic AlCoCrFeNi alloy samples were prepared by induction melting and mechanical alloying (MA) combined with spark plasma sintering (SPS). The cast sample showed a dendritic microstructure composed of spinodally decomposed nanometric constituents of the B2 and BCC phases. The spark plasma sintered sample exhibited an ultrafine-grained microstructure of B2 phase and FCC solid solution and Cr23C6 carbides. The MA + SPS sample was strengthened by compressive stress-strain test up to a yield strength of 2029 ± 5 MPa, resulting significantly higher compared to 1366 ± 32 MPa of the cast sample. In addition to the higher compressive yield strength, the sintered sample exhibited a hardness of more than 130 HV higher compared to the cast alloy. On the other hand, the cast alloy showed high plastic deformation (29%) and significantly high ultimate compressive strength of 3072 ± 122 MPa. Together with these mechanical characteristics, the MA + SPS sample showed good thermal stability while preserving the mechanical properties even after annealing at 800 °C. This was not the case with the cast sample, in which ductility and ultimate strength significantly decreased upon annealing at 800 °C. A substantial yield strength reduction of both MA + SPS and cast samples was recorded when tested at 800 °C. Nevertheless, stress-strain curve trends were observed to be quite different between the two samples, thus suggesting dissimilar deformation mechanisms under high-temperature compression.

Microstructure and wear behaviour of AlCoCrFeNi-coated SS316L by atmospheric plasma spray process

ABSTRACT The capacity to endure harsh wear in demanding conditions in stainless steel drops under extreme nature and applications. Protecting the surface by providing a coating layer supports the usage in harsh conditions. In this work, SS316L is coated with AlCoCrFeNi high-entropy alloy (HEA) by atmospheric plasma spray process and annealed at 600°C for 2 hours. The AlCoCrFeNi HEA exhibited spherical particles with bcc phase and 20 µm particle size. The coating morphology revealed a uniform coating with a homogeneous distribution of HEA particles over a thickness of 150 µm. The coating post-annealing offered improved microhardness by 12% than the coated sample before annealing. The wear test was executed by varying load, sliding distance, and sliding velocity at normal temperature, 400°C and 600°C and the corresponding worn surface was analysed. The coated samples after annealing showed 57.6%, 87.5%, and 65.4% improved wear resistance at normal temperature than the coated sample before annealing at minimum levels of load, sliding velocity and distance. The wear rate of coated and annealed samples revealed 5.2%, 4.5%, and 4.4% better wear resistance at 400°C than the coated samples before annealing. The worn surface morphology showcased wear mechanisms to be delamination, abrasive wear, and oxide layer formation under all conditions.

Powder Synthesis and Characterization of Al0.5CoCrFeNi High-Entropy Alloy for Additive Manufacturing Prepared by the Plasma Rotating Electrode Process.

The Al0.5CoCrFeNi high-entropy alloy powder was produced by using a plasma rotating electrode process. The morphology, microstructure, and physical properties of the powder were characterized. The powder exhibited a smooth surface and a narrow particle size distribution with a single peak. The relationships between particle size and secondary dendrite arm space as well as cooling rate were evaluated as follows: λ = 0.0105d + 0.062 and vc = 4.34 × 10-5d-2 + 2.62 × 10-2d-3/2, respectively. The Al0.5CoCrFeNi powder mainly consisted of fcc + bcc phases. As the powder particle size decreased, the microstructure of the powder changed from dendritic to columnar or equiaxed, along with a decrease in the fcc content and an increase in the bcc content. The tap density (4.76 g cm-3), flowability (15.01 s × 50 g-1), oxygen content (<300 ppm), and sphericity (>94%) of the powder indicated suitability for additive manufacturing.

HARDENING BEHAVIOR OF ADVANCED STRUCTURAL ALLOYS UNDER ION IRRADIATION

In this study, a series of recently developed alloys, including multi-principal element alloys with FCC and BCC phase structure, ODS-modified austenitic steel, and T91 ferritic-martensitic steel modified with severe plastic deformation have been investigated with respect to the hardening/embrittlement phenomenon under irradiation. Samples of all materials were irradiated under identical conditions with 1.4 MeV Ar ions at room temperature. Transmission electron microscopy (TEM) was used to characterize the radiation defects and microstructural changes. Nanoindentation was employed to measure the effect of ion irradiation on hardening. The dependence of the hardening parameters on the irradiation dose, their relationship with the evolution of the microstructure was studied. It was found, that the developed alloys exhibited a reduced susceptibility to irradiation induced hardening compared to that of conventional SS316 and 18Cr10NiTi stainless steels. The study discusses the mechanisms that can affect the radiation hardening behavior in examined materials.

Zirconium-Modified Medium-Entropy Alloy (TiVNb)85Cr15 for Hydrogen Storage.

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb)85Cr15, a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase (HEA1) is the primary hydrogen absorber, while the minor phases HEA2 and HEA3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb)81Cr15Zr4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage.

Microstructural evolution and mechanical behavior of novel TiZrTaxNbMo refractory high-entropy alloys

The refractory high-entropy alloy (RHEA) with a body-centered-cubic (BCC) solid-solution structure has excellent high-temperature softening resistance, which has attracted wide interest in the field of high-temperature alloys. However, its limited room-temperature plasticity has greatly hindered its engineering application. To obtain an excellent strength-plasticity matching relationship, in this reported study, the Ta content in the high-entropy alloy (HEA) was adjusted to rectify this shortcoming. A series of TiZrTaxNbMo (x = 1.0, 0.9, 0.8, 0.7, and 0.6 at. percent, at%) RHEAs were prepared using the vacuum arc-melting technique, and the microstructure and mechanical properties of these RHEA alloys were systematically investigated. The experimental results show that the TiZrTaxNbMo RHEAs are composed of main BCC1 and minor BCC2 phases, which exhibit a dendritic structure. By reducing the Ta content, the elemental segregation caused by the non-equilibrium solidification is reduced. In terms of mechanical properties, with the decrease of Ta content, the hardness and room-temperature yield strength of the alloy decreases slightly, but the room-temperature plasticity increases significantly. The Ta0.7 alloy has the highest plasticity (34.8 %), which is about twice that of the equimolar Ta 1.0 alloy, while the yield strength remained at 1297 MPa. The excellent mechanical properties of the alloys can be attributed to solid-solution strengthening and the formation of moderate amounts of interdendritic regions. The interaction between slip bands and dislocations formed during compression of the Ta0.7 alloy decreased its work hardening. Moreover, the theoretical model of solid-solution strengthening elucidates that the calculated values of the alloy’s yield strength are consistent with that obtained experimentally.