The influence of nanocrystalline CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy particles addition on microstructure and mechanical properties of SiCp/7075Al composites

Abstract

The influence of nanocrystalline CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy (HEA) particles addition on the microstructure and mechanical properties of SiCp/7075Al composites was investigated systematically. The CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy was prepared by mechanical alloying, and the (5 vol% HEAp + 40 vol% SiCp)/7075Al (HEA-7075Al) and 45 vol% SiCp/7075Al (SiC-7075Al) composites were subsequently fabricated by squeeze casting. The HEA particles were well retained in the Al matrix and remained nanocrystalline following the squeeze casting and heat treatment process, which indicated that the CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy has the advantage of sluggish diffusion behavior and thermal stability. The time for the HEA-7075Al composite reaching the aged-peak period (19.5 h) was slightly longer than that of the SiC-7075Al composite (15 h), indicating that the HEA particles addition has postponed the aging process, which can be ascribed to the decrease of dislocation density in the Al matrix, evaluated from XRD. Additionally, in contrast to the SiC-7075Al composite, the HEA-7075Al composite exhibits higher strength, better plasticity and higher modulus with the average values of 712 MPa, 0.82% and 171 GPa, respectively, which is the results of the good interface between HEA particles and Al matrix, high strength nanocrystalline HEA particles and proper dislocation density present in Al matrix.