Ageing behaviour of equiatomic consolidated Al20Co20Cu20Ni20Zn20 high entropy alloy

The effect of ageing treatment on the evolution of microstructure and hardness of consolidated Al20Co20Cu20Ni20Zn20 high entropy alloy is reported. The consolidated alloy specimens were solutionized by heat treatment at 1433K for 96h. The solutionized specimens were subsequently subjected to ageing treatment at 673, 773, 873 and 1073K for 48h to investigate the effect of ageing treatment on the evolution of microstructure as well as micro-hardness of the alloy. The fully solutionized specimens reveal formation of single phase FCC β phase. The artificially aged alloy consists of Ni and Al rich FCC α (L12) precipitate in FCC (γ) matrix. This is akin to precipitation in Ni-based superalloys. The hardness measurement of the aged specimens indicate peak age-hardening (~6.2GPa) at 773K. Therefore, the present study demonstrates possibility of age hardening of consolidated alloys akin to sinter ageing.