Physical-metallurgical properties and micro-milling machinability evaluation of high entropy alloy FeCoNiCrAl_x

High-entropy alloy (HEA) belongs to the emerging multi-principal alloy with excellent mechanical-physical properties. The material machinability is critical for cutting planning, especially for novel materials with various chemical compositions and mechanical properties. The machinability of high-entropy alloys mainly depends on the physical-metallurgical properties and cutting conditions. This work investigated the physical-metallurgical properties and micro-machinability of HEA FeCoNiCrAl_x (x = 0.1, 0.5, 1) with vacuum arc melting preparation. Experimental results indicated that the difference of Al element content affected the chemical element distribution, phase composition, microstructure, and microhardness of prepared HEA FeCoNiCrAl_x. FeCoNiCrAl_0.1 appeared single face-center-cubic (FCC) structure, while the increase in Al element content led to dual face-center-cubic and body-center-cubic (FCC + BCC) structure for FeCoNiCrAl_0.5 and FeCoNiCrAl₁. The average microhardness values were approximately 183 HV, 294 HV, and 461 HV for FeCoNiCrAl_0.1, FeCoNiCrAl_0.5, and FeCoNiCrAl₁, respectively. The increase in Al element content led to poor material machinability, in which FeCoNiCrAl_0.1 had better machinability due to lower micro-milling forces, more stable cutting process, lower specific cutting energy, better surface qualities and smaller tool wear. This work combined the prepared material properties and micro-machinability evaluation to guide HEA design and select practical machining parameters.