Effects of Ge addition on the structure, mechanical and magnetic properties of (CoCrFeNi)100-xGex high-entropy alloys

Abstract

Alloying non-metallic elements can not only change the structure of alloys, but also tailor the mechanical and physical properties. The microstructure, mechanical and magnetic properties of (CoCrFeNi)100-xGex (molar ratio, x = 0 ∼ 33) high-entropy alloys (HEAs) have been systematically studied in this paper. The experimental results show that the (CoCrFeNi)100-xGex HEAs transform from a face-centered cubic (FCC) to a body-centered cubic (BCC) solid solution when 10 ≤ x ≤ 25, and a hexagonal intermetallic compound (IM) formed at x = 33. Tensile measurement revealed that the strength and plasticity of the alloy were enhanced simultaneously with Ge addition in the single FCC region (x ≤ 10), a decrease in ductility but sharp increase of strength was found in the alloys when the BCC phase starts to appear. Theoretical calculations and magnetic hysteresis loop measurements show that the alloys transform gradually from a paramagnetic to a ferromagnetic state at room temperature.