Effect of sintering temperature on microstructure evolution and mechanical properties of Al0.5CoCrFeNi high entropy alloy prepared by Spark Plasma Sintering

In this study, the effect of sintering temperature on the microstructure evolution and mechanical properties of Al_0.5CoCrFeNi high-entropy alloy (HEA) was systematically investigated using Spark Plasma Sintering (SPS). By combining experimental methods and molecular dynamics simulations, the densification behavior, phase composition, grain size, dislocation density, and mechanical properties of the high entropy alloy sintered at 900 °C, 1000 °C and 1100 °C were studied. The experimental results showed that with increasing sintering temperature, the porosity decreased significantly (fully densified at 1100 °C), the content of the BCC phase decreased and the content of the FCC phase increased, while the average grain size increased markedly. The mechanical properties exhibited significant temperature dependence. The HEA exhibited optimal mechanical performance at a sintering temperature of 1000 °C, achieving a yield strength of 717 MPa and a tensile strength of 1022 MPa. The yield strength and tensile strength at 1000 °C increased by 54.5 % and 68.0 %, respectively, compared with those of the sample sintered at 900 °C. Molecular dynamics (MD) simulations revealed that increasing sintering temperature accelerates densification by enhancing atomic diffusion, which evolves from surface diffusion at lower temperatures to grain boundary diffusion and ultimately to bulk (lattice) diffusion at higher temperatures. Theoretical analysis indicates that the sintering temperature optimizes the synergy between strength and ductility of HEA by dislocation evolution, recrystallization, and phase transformation, thereby providing a theoretical foundation for the process design of Al_0.5CoCrFeNi HEA.