Excellent strengthening effect of L12 precipitates on the selective laser melting Al0.3CoCrFeNiCu high entropy alloy via annealing treatment

Abstract The influence of annealing treatment on the microstructure and mechanical properties of single phase structural Al0.3CoCrFeNiCu high entropy alloy (HEA) fabricated by selective laser melting (SLM) were investigated. The results indicated that the L12 precipitates were dispersed in matrix and also enriched at sub-grain boundaries of the SLM specimens annealed at 600 °C for 10 h. Besides, wetting transition was observed at the sub-grain boundary. Meanwhile, the microhardness and room compressive yield strength of this as-built HEA were dramatically enhanced from 255 HV and 419 MPa to 357 HV and 647 MPa after annealing treatment, respectively. Besides, the as-annealed HEA still possessed considerable ductility. Based on the microstructure analysis, the strength mechanism of as-annealed alloy was ascribed to the nano-sized L12 precipitates in sub-grains and also their enrichment at the sub-grain boundaries.