Static recrystallization and grain growth behaviour of Al0.3CoCrFeNi high entropy alloy

Single phase Al 0.3 CoCrFeNi (Al 0.3 ) FCC high entropy alloy (HEA) synthesized through arc melting was subjected to cold rolling and subsequent annealing to study its recrystallization and grain growth behaviour. For the as-cast alloy, only partial recrystallization was achieved after cold deformation followed by annealing at 800 and 900 °C, which was attributed to the pining effect of Al–Ni rich precipitates formed during annealing. The activation energy of static recrystallization (549 kJ/mol) for the as-cast Al 0.3 HEA was significantly higher than that of conventional alloys due to the distorted lattice, sluggish diffusion and most importantly the interaction of Al–Ni rich precipitates with the recrystallization. Homogenization heat treatment on Al 0.3 HEA increased the static recrystallization kinetics and was associated with the lower volume fraction of precipitates formed during annealing. An increased grain growth exponent (n ≈ 5) and activation energy (583 kJ/mol) compared with conventional alloys, particularly at low annealing temperatures, was observed for the Al 0.3 HEA mainly due to the pinning effect of Al–Ni rich precipitates. Finally, through investigating the mechanical performance of the alloy after annealing in the precipitation-free (1050 and 1000 °C) and precipitation-containing (900 °C) temperature ranges, the relative contributions for grain boundary and precipitation strengthening were estimated for the annealed Al 0.3 HEA.