High-entropy Alloy Particles Research Articles

Enhanced mechanical properties of aluminum matrix composites reinforced with high-entropy alloy particles via asymmetric cryorolling

To achieve higher performance of aluminum matrix composites (AMCs), high-entropy alloy particles (HEAp)-reinforced AMCs sheets were processed via asymmetric rolling (AR, 298 K) and asymmetric cryorolling (ACR, 77 K) methods. The mechanical properties and microstructure of the HEAp/AMCs were analyzed by tensile tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results suggest that ACR improved the mechanical properties of HEAp/AMCs to a higher degree than AR. The ultimate tensile strength (UTS) of ACR 3 wt.% HEAp/AMCs reached 253 MPa, which was 13.5% higher than that achieved with AR. ACR resulted in fewer microvoids, finer grain sizes, and higher dislocation density in HEAp/AMC sheets compared to AR. Such a reduction of defects during ACR can be attributed to the volume shrinkage effect of the HEAp/AMCs in the cryogenic environment.

Microstructure and properties of FeCoNiCrMn and Al2O3 hybrid particle-reinforced aluminum matrix composites fabricated by microwave sintering

In this paper, multiscale Al2O3 micro/nanoparticles (0–14 wt%) mixed with FeCoNiCrMn high-entropy alloy (HEA) particles (15 wt%) were used as reinforcements to prepare dual-phase-reinforced aluminum matrix composites (AMCs) through microwave sintering. The strengthening effects of doping different weight fractions of Al2O3 micro/nanoparticles on the microstructure, mechanical properties, and strengthening mechanisms of the mixed-phase particle-reinforced AMCs were investigated. The performance after 11 wt% Al2O3+HEA microparticles was similar to that obtained by adding 2 wt% and 5 wt% Al2O3+HEA nanoparticles. The hardness, yield strength, and compressive strength of the 2 wt% nano-Al2O3 composite were 109.7 HV, 286.5 MPa, and 506.7 MPa, respectively, which were 70.9%, 98.5%, and 94.7% higher than those of the single HEA-reinforced sample. In terms of the strengthening and toughening mechanisms, Orowan strengthening, dislocation strengthening, and thermal mismatch strengthening were the main strengthening mechanisms of particles species mixed in the metal matrix composites. Hall-Petch strengthening and load-transfer effects were mainly attributed to the cross-scale mixing of particles. The hybrid particles of HEA and Al2O3 synergistically delayed interfacial crack propagation. This study provides a new preparation method for high-performance metal matrix composites.

Microstructure and properties of FeCoNi1.5CrCup/Al high-entropy alloy strengthened aluminum matrix composites and finite element simulation

In this study, high-entropy alloy (HEA) particles were used as the reinforced phase to prepare a high strength-toughness FeCoNi1.5CrCup/Al aluminum matrix composite. On the condition of different HEA adding amount, the microstructure and macro/micro mechanical properties together with their relationship are characterized. The finite element simulation is conducted to calculate the macro/micro mechanical properties and acquire a well-fitting with the experimental data. The research shows that when the HEA adding amount is 15 wt%, the particulate size is moderate and evenly distributed in the matrix, the HEA/Al interface is tightly bonded and no impurity phase is formed. The corresponding yield, compressive strengths and maximum compression ratio are 202.6 MPa, 391.2 MPa and 59.7% separately, which reaches an optimized high level. The particulate, dislocation and interface strengthening mechanisms are regarded as the main positive factors. The created "HEA/Al composite micro/macro performance simulation" finite element model provides a new scheme and technical route for the design, preparation and mechanical properties research of new composite materials.

The effect of cryogenic treatment on the microstructure and room-temperature mechanical properties of the (HEAp/Al) at different temperatures

At present, high entropy alloy particle reinforced aluminum matrix composites (HEAp/Al) have some shortcomings in performance. For example, it has high strength but low plasticity and processability. This paper mainly investigated how the different cryogenic temperature (−50 ℃, −100 ℃ and-196 ℃) affects the properties of (FeCoNi1.5CrCu)p/Al composites. When the cryogenic temperature drops, the maximum compression ratio (δ) and fracture energy of (FeCoNi1.5CrCu)p/Al composites enhances. The optimized − 196 ℃ sample exhibits the maximum δ of 25.21% and 5.31 × 107 J/m3 fracture energy that corresponds to high plasticity, toughness and Schmidt factor (SF). It also reaches the maximum nano-indentation and elastic modulus in the inter-diffusion layer. The enhancement of performance is attributed to its high compactness, fine HEA particles, nanometer-sized Cr precipitates around HEAP. After DCT, we can find that refined grains, massive high-angle boundary grains, induced texture are connected with the recrystallization and free energy. But those positive factors are counteracted by the significant decrease of dislocation density, which directly results in the decrease of compression strength.

Fabrication, microstructure, and mechanical properties of Al-based metal matrix-TiB2 -HEA hybrid composite

In this work, a metal matrix composite is made up of a cast Al-Si-Mg alloy (LM25) matrix with two variants of particle reinforcements, first one with 3 wt% TiB2 and 2 wt% CoCrFeMnNi high entropy alloy (HEA) and the other as 2 wt% TiB2 and 3 wt% CoCrFeMnNi (HEA) were used. These two composites were successfully fabricated through the stir-casting process. The microstructures and morphology of the developed composites are studied using TEM and SEM. In the fabricated composites, TiB2 and HEA particles were discovered to be evenly dispersed in the matrix phase. The XRD analysis showed the existence of both the reinforcement phases TiB2 and HEA particles along with the matrix phase. The mechanical properties were enhanced with the addition of the reinforcement phase when compared with the base metal. It is also observed that the tensile strength is enhanced with increased HEA content demonstrating almost same ductility. The LM25–2 wt% TiB2 − 3 wt% HEA composite demonstrated higher tensile strength (∼255 MPa) than the LM25–3 wt% TiB2-2 wt% HEA composite (∼230 MPa) and LM25 base alloy (∼160 MPa) due to the presence of TiB2 and HEA particles and the high dislocation density and contrasted very well in terms of strength and ductility with conventional LM25 matrix composites supplemented with ceramic particles. The mode of fracture was observed that the cleavage planes on the fracture surface with increasing with HEA content changes from dimple morphology of base metal.

Effects of Heat Treatment on the Interface Microstructure and Mechanical Properties of Friction-Stir-Processed AlCoCrFeNi/A356 Composites

Equiatomic AlCoCrFeNi high-entropy alloy (HEA) has gained significant interest in recent years because of its excellent mechanical properties. A356 aluminum alloy reinforced by AlCoCrFeNi HEA particles was fabricated by friction stir processing (FSP) and subsequent heat treatment. Solution and aging treatments were specially performed for the composites to control the interface microstructure, and interfacial microstructure and tensile properties were explored at different conditions. The interface between the matrix and HEA particles showed a dual-layered core-shell structure and the thickness of the shell region increased with the solution time. The microstructure located in the shell layers consisted of a solid solution with increasing aluminum content, in which a radial-shaped solid solution phase formed in the region close to the core of the HEA particle and scattered solid solution grains with high Ni content formed in the region close to the matrix alloy. The gradient of composition and microstructure across the HEA/Al interface can be obtained through heat treatment, and an optimal interface bonding state and mechanical property were obtained after solution treatment for 2 h. Compared with FSPed A356 aluminum alloy, the FSPed composite enhanced the tensile stress by 60 MPa and the stain by 5% under the optimized conditions. The overgrowth of the shell layer decreased both the tensile strength and the ductile greatly due to the formation of a radial-shaped solid solution phase in the shell region.

Formation mechanism of interdiffusion layer and mechanical properties of Al0.6CoCrFeNi high-entropy alloy/Ti composites

The 10 vol% Al0.6CoCrFeNi high entropy alloy (HEA) particles reinforced titanium matrix composites were fabricated successfully by hot pressing sintering under vacuum. The formation mechanism of interdiffusion layer and mechanical properties of the composites were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), back scattered electron (BSE), electron backscatter diffraction (EBSD) and compressive test. The results show that the interdiffusion layers composed of AlNi2Ti (BCC) and Ni-Ti mixed phases (FCC) are formed between the HEA particles and the matrix. The recrystallization mechanism of the composites is continuous dynamic recrystallization and second phase particle induced recrystallization. The concentration gradient and mixing enthalpy were the main driving force for the formation of phase in interdiffusion layer. The formation sequence of Ni-Ti mixed phases is NiTi2, NiTi and Ni3Ti. The compressive strength (1642 MPa) of the composites with the same strain (21.7%) is 86.1% higher than that of the pure titanium samples (882.5 MPa). During the compression process, cracking occurs at the Ni-Ti mixed phases interdiffusion layer.

Microstructure and properties of FeCoNiCrAl high-entropy alloy particle-reinforced Cu-matrix composites prepared via FSP

Although copper has excellent thermal conductivity, poor wear resistance seriously limits its development. In this paper, a Cu matrix surface composite material reinforced by FeCoNiCrAl high-entropy alloy particles was prepared by friction stir processing. The microstructure and properties of the composite were investigated. The results showed that both the FSP process and the addition of HEA particles contributed to the refinement of the Cu-matrix grains. A diffusion layer with a width of about 0.8 µm was formed at the interface between the HEA particles and the Cu matrix. Compared with received Cu, the microhardness of Cu matrix in the composites was increased by 69.8%, the wear rate was reduced by 29.7%, and the wear resistance was significantly improved. Mean while, the ductility of the composite was consistent with that of the received Cu, and the thermal conductivity reached 87% of the received Cu. Therefore, this paper provided a new possibility for developing multifunctional structural materials with high wear resistance, high ductility, and high thermal conductivity.

Effect of reinforcement types on the ball milling behavior and mechanical properties of 2024Al matrix composites

In this paper, 2024 Al matrix composites reinforced by nanocrystalline high-entropy alloy particles (NC-HEAp), SiC particles, and coarse-grained high-entropy alloy particles (CG-HEAp) were fabricated via powder metallurgy, and a comparative study of different reinforcements was deeply conducted. The results showed that reinforcement types significantly influenced the morphology of composite powders, and the grain size and interfacial condition of composites. After ball milling, irregular granular NC-HEA-Al and SiC–Al composite powders were produced while the CG-HEA-Al composite powders exhibited flake shapes, and particle size of NC-HEAp sharply decreased and was significantly smaller than the other two reinforcements. The Cu-rich diffusion layer, a high dislocation density, and a thin oxide layer were formed in the interfaces of NC-HEA-Al, SiC–Al, and CG-HEA-Al composites, respectively. The NC-HEA-Al composite possessed the highest strength due to the best effect of grain refinement, while the SiC–Al composite displayed better ductility attributed to higher work hardening rate after the yield stage than that of the NC-HEA-Al composite. The CG-HEA-Al composites showed the least attractive mechanical properties, related to a poor interface bonding and pre-existing cracks in CG-HEAp. Furthermore, the differences in strengthening mechanisms of the three composites were also discussed. This work provides guidelines for designing metal matrix composites fabricated by powder metallurgy.

Mechanical properties of Al-Si matrix composites synergistically reinforced by high-entropy alloy and SiC nanoparticles

To improve the mechanical strength and ductility of Al-20Si matrix composites, a novel strategy was proposed by constructing nanoparticle-rich zones (NPR) in where SiC nanoparticles were embedded into fine-grain high-entropy alloy particles (SiC@HEA). Due to the specific arrangement of SiC in HEA reinforcement, the mechanical properties of as-fabricated Al composites with hierarchical microstructure were improved significantly. The influences of hierarchical structure and interface between the NPR zones and Al matrix on tensile strength and ductility were systematically studied. The results show that the designed composite exhibits NPR zones and nanoparticle-free (NPF) zones, leading to a typical bimodal structure. The NPR zones have a higher density of geometrically necessary dislocations (GND) than NPF zones, and hence it can act as “hard” regions by enhanced dislocation strengthening and grain refinement. The large Al grains in NPF zones actet as “soft” regions to promote plastic deformation. The SiC@HEA/Al interface featured a dual-layer, including the inner layer (∼200 nm) of Ni2Si, FeNi, Ni3Si2, and FeSi phases, and the outer layer (∼300 nm) of Ni5Si2, Ni2Si, and FeNi phases. A good combination of tensile strength (251 MPa) and elongation (9%) was realized in SiC@HEA/Al composite. This study provides a new route to fabricate composites with enhanced both strength and ductility.

Microstructures and mechanical properties of AlCoCrFeNi2.1/6061-T6 aluminum-matrix composites prepared by friction stir processing

A novel 6061-T6 aluminum matrix composites reinforced by AlCoCrFeNi2.1 high-entropy alloy (HEA) were obtained using friction stir processing (FSP), and the resultant composites were further strengthened by T6 heat treatment. The effects of reinforcement phase content on the microstructure and mechanical properties of composites were investigated. The results indicate that AlCoCrFeNi2.1 HEA is suitable as a reinforcement material to strengthen the aluminum matrix, which effectively suppressed the formation and growth of intermetallic compounds unlike selecting pure metal particles as reinforcements. As the content of HEA reinforcement increased, the recrystallization degree of composites increased, while the grain size decreased. The continuous and dense interface zone shows sound metallurgical bonding between the aluminum alloy matrix and HEA particles. Owing to the low processing temperature of FSP, the drastic chemical reaction can be effectively avoided, and there were no intermetallic compounds formed at the interface. The hardness and tensile strength of the composites improved with the reinforcement content. Compared with friction stir processed-6061, the hardness and tensile strength of the composites with 15% HEA increased by 28.6% and 25.6%, which reached 72 HV and 222.9 MPa respectively. After T6 aging heat treatment, the hardness and the tensile strength reached 125 HV and 332.1 MPa, further improved by 73.6% and 49.0%, respectively. It shows that Hall-Petch and thermal mismatch strengthening played the significant positive influences to strengthening, and Orowan strengthening made the least contribution. The findings can promote the wide application of aluminum-matrix composites in the automotive, marine and aerospace industries.

Effect of asymmetric rolling on microstructure and mechanical properties of aluminum matrix composites

The lightweight of structural materials was an important research focus for reduced energy consumption and transport efficiency. Aluminium matrix composites (AMCs) had the advantages of high specific strength and good wear resistance, so they were widely used in automobile, aerospace and other fields. At present, the deformation mechanism of AMCs reinforced by high-entropy alloy particles (HEAp) in asymmetric rolling was not clear. In this work, AMCs ingot reinforced with 6 wt% HEAp was prepared by stir casting process. Then the mechanical properties of HEAp/AMCs under different rolling processes were studied by asymmetric rolling (AR) and asymmetric cryorolling (ACR) processes. High-entropy alloy (HEA) had excellent strength and toughness, which imparted good deformation ability when added to AMCs as reinforcement. The microstructure of AMCs reinforced by HEAp was refined by ACR. At the same time, the HEAp/AMCs obtained by ACR displayed a higher ultimate tensile strength (UTS) than that obtained by AR. The study of ACR shows that AMCs reinforced with HEAp have good toughness. ACR can reduce the thickness of HEAp/AMCs to a greater extent so as to produce AMCs strip with excellent mechanical properties.

Stir Casting and Successive Rolling of Aluminium Alloy 2218 MMCs Reinforced by High-Entropy Alloy Particles

Al0.5CoCrFeNi high-entropy alloy (HEAp) reinforced AA2218 metal matrix composites (MMCs) by stir casting and successive rolling. Mechanical characteristics of the AA2218 HEAp MMCs are analysed. The stir-casted AA2218 HEAp MMCs' ultimate tensile strength rose by 74.3 percent when HEAp was added at a weight percentage of 4 wt percent. When the MMCs were made by rolling, they had greater mechanical qualities than those made by RTR. Higher rolling deformation and lower HEAp mass fraction led to greater mechanical characteristics discrepancies between the AA2218 HEAp MMCs formed by CR and RTR. In the AA2218 HEAp MMCs after RTR, there were voids that were not present in the CR MMCs. Micro holes and the mechanical properties of metal matrix composites were also discussed in detail.

High-Entropy Alloy Aerogels: A New Platform for Carbon Dioxide Reduction.

High-entropy alloy aerogels (HEAAs) combined with the advantages of high-entropy alloys and aerogels are prospective new platforms in catalytic reactions. However, due to the differences in reduction potentials and miscibility behavior of different metals, the realization of HEAAs with a single phase is still a great challenge. Herein, a series of HEAAs is fabricated via the freeze-thaw method as highly active and durable electrocatalysts for the carbon dioxide reduction reaction (CO2 RR). Especially, the PdCuAuAgBiIn HEAAs can achieve Faradaic efficiency (FE) of C1 products almost 100% from -0.7 to -1.1V versus reversible hydrogen electrode (VRHE ), and a maximum FE for formic acid (FEHCOOH ) of 98.1% at -1.1VRHE , outperforming PdCuAuAgBiIn high-entropy alloy particles (HEAPs) and Pd metallic aerogels (MAs). Specifically, the current density and FEHCOOH are almost 200mAcm-2 and 87% in a flow cell. The impressive CO2 RR performance of the PdCuAuAgBiIn HEAAs is attributed to the strong interactions between the different metals and the surface unsaturated sites, which can regulate the electronic structures of different metals and allow the optimal HCOO* intermediate adsorption and desorption onto the catalysts surface to enhance HCOOH production. The work not only provides a facile synthetic strategy to fabricate HEAAs, but also opens the avenue for development of efficient catalysts and beyond.

Interface structure and tensile behavior of high entropy alloy particles reinforced Al matrix composites by spark plasma sintering

Aluminum matrix composites (AMCs) reinforced with AlCoCrFeNi high entropy alloy (HEA) particles were fabricated by spark plasma sintering (SPS). The interface formation between the HEA particles and Al matrix, tensile properties and fracture behavior were investigated. The interface has a two-layer structure, the interface reaction layer close to the HEA particles was Al13(CoCrFeNi)4, and the interface reaction layer near the Al matrix was composed of Al9(CoFeNi)2 and Al18Cr2Mg3. The addition of HEA particles increased the yield strength, and reduced tensile strength and elongation of the composites. The fracture occurred at the interface reaction layer near the HEA particles, exhibiting obvious brittle fracture feature. The tensile fracture mechanism of the SPSed HEA/Al AMCs can be attributed to the poor plastic deformation ability of continuously distributed Al13(CoCrFeNi)4 and aggravated degree of stress concentration at interface reaction layer close to the HEA particles.

Multiple strengthening via high-entropy alloy particle addition in titanium matrix composites fabricated by spark plasma sintering

The strong interface bonding of particle reinforced metal matrix composites has been a longstanding puzzle. Unlike the existing titanium matrix composites (TMC) processed, which are mainly reinforced by ceramic particles, this work investigates the in-situ triggered alloying via high entropy alloy (HEA) addition, which promotes multiple strengthening to the metal matrix. The effects of HEA content on the microstructure evolution, mechanical properties, void growth mechanism, sintering model and underlying strengthening mechanism were investigated. The results show that the enhanced diffusion effect in the diffusion region leads to the formation of a multiphase structure composed of an FCC solid solution and a σ phase. In addition, with the addition of HEAs content, the yield strength and hardness values of all composites were higher than those of unreinforced Ti6Al4V (TC4). The obtained composite reinforced with 4.5 wt% HEA achieves an unprecedented tensile elongation to failure of 8.8% and a high ultimate tensile strength of 1150 MPa. The enhancement of the strength is attributed to the combined effects of grain refinement strengthening, load transfer strengthening and dislocation strengthening.

Interface characteristics and mechanical properties of Al0.6CoCrFeNi/5052Al matrix composites fabricated via vacuum hot-pressing sintering and annealing

In this study, Al0.6CoCrFeNi high-entropy alloy particle reinforced 5052Al matrix composites prepared via vacuum hot-pressing sintering were annealed. Experimental techniques such as SEM, XRD, EPMA, Vickers hardness, and uniaxial compression were used to characterize the prepared composites' microscopic morphology and mechanical properties. Furthermore, the Boltzmann-Matano diffusion theory and diffusion layer thickness curve fitting methods were used to predict the trend of the thickness of the diffusion layer under various annealing conditions. The results of this study suggest that the thickness of the diffusion layer increased parabolically with an increase in annealing temperature or annealing time. The intermetallic compounds (IMCs) generated in the diffusion layer region were Al13Co4-, Al9Co2-, and Al18Cr2Mg3-type phases. The mechanical properties of the composites were closely related to the change in the thickness of the diffusion layer: when the annealing temperature was 773 K/8 h, the compressive strength and microhardness of the composites reached the maximum values of 345.7 MPa and 82.8 HV0.2, respectively. Furthermore, the linear fitting method with the addition of the incubation period provided the best fit to the experimental values and provided a reference for subsequent modulation of the composite properties by varying the thickness of the diffusion layer.

High entropy alloy reinforced aluminum matrix composites prepared by novel rotation friction extrusion process: Microstructure and mechanical properties

A novel rotation friction extrusion (RFE) process was taken to fabricate CrMnFeCoNi high entropy alloy (HEA) particles reinforced aluminum matrix composites (AMCs). The experimental methods and the first principle calculation based on density functional theory were employed to study the microstructure and mechanical properties of the composites. Results showed that the HEA particles reacted violently with the aluminum (Al) matrix during RFE. The average grain size of the AMCs was 3.6 μm, which was significantly lower than that of the RFEed Al (13.2 μm). Numerous second phases with FCC structure were formed, as a result of the large thermodynamic driving force and the enhanced element interdiffusion. The tensile strength of the AMCs showed substantially enhanced compared to that of RFEed Al, which could be ascribed to load transfer, dislocation strengthening, fine-grained strengthening and Orowan strengthening. The uniform elongation of the AMCs was lower than that of the RFEed Al, which was explained by the fine grain size of the AMCs resulting in high dislocation dynamic recovery rate.

Tribological behavior of high-entropy alloy particle reinforced aluminum matrix composites and their key impacting factors

Al0.5CoCrFeNi high-entropy alloy particles reinforced aluminum matrix composites (HEAps/AMCs) with various reinforcement additions (0.5, 1.5, 3.0, and 5.0 wt%) were fabricated. The coefficient of friction (COF, about 0.45–0.47) and wear rate (0.32–0.40 10–3 mm3/Nm under 30 N) of HEAps/AMCs tribosystems with a moderate range of reinforcement (0.5–3.0 wt%) were lower than the matrix alloy. HEAps hindered plastic deformation of the contact surface, increasing the wear resistance of the AMCs. Due to the tight interface and the interaction between the HEA particles and dislocations, the AMC was stabilized during the wear tests and showed a dramatically improved capacity to resist crack initiation, propagation, and fracture around the interface.

Properties of AlFeNiCrCoTi0.5 High-Entropy Alloy Particle-Reinforced 6061Al Composites Prepared by Extrusion

(AlFeNiCrCoTi0.5)p/6061Al matrix composites were prepared by cold isostatic pressing combined with equal-diameter angular extrusion. The microstructure and properties of the extruded materials after adding high-entropy alloys were studied. The FCC + BCC dual-phase high-entropy alloy particles mechanically alloyed for 90 h were added to the aluminum matrix, while the composite material formed a diffusion interface after equal-diameter angular extrusion. Compared with the 6061Al matrix, when the content of AlFeNiCrCoTi0.5 was 10%, by two passes, the hardness increased from 52.5 HV to 70.3 HV, the tensile strength increased from 158 MPa to 188 MPa, and the elongation changed from 14.9% to 14.1%. The material had good comprehensive mechanical properties.