Microstructure and mechanical property of novel nanoparticles strengthened AlCrCuFeNi dual-phase high entropy alloy

Abstract

High entropy alloys are considered to be the best candidates for structural materials because of outstanding comprehensive properties resulted from their unique microstructure. Clarifying the microstructural evolution and controlling the content and morphology of the second phase are of great significance in the design of high-performance HEAs. Along this line of thinking, we report a research of adding little Mo(0–0.5 at%) to a novel Co-free AlCrCuFeNi alloy to tailor microstructure by introducing large lattice distortion and precipitation strengthening to achieve excellent comprehensive properties. The AlCrCuFeNi alloy exhibits BCC+FCC dual-phases, typical solid solution structures (B2 matrix, A2 flap-like and Cu-rich structure) and moderate mechanical properties. An ultrahigh hardness of 643 HV was achieved at the composition of Mo reaches 0.5 at%, which is approximately 1.5 times higher than AlCrCuFeNi alloy. A large amount of nano-sized σ precipitates with various sizes and morphologies were formed when the content of Mo was more than 0.3 at%. Most importantly, the Mo0.3 alloy exhibits an increase of ~18% in yield strength and an increase of ~30% in fracture strength accompanied by a reasonable plasticity which possesses potential application prospects in industrial areas. The solid solution strengthening and the formation of σ phase are the main factors contributing to the strengthening.