Class I type creep behavior of coarse-grained Al0.5CoCrFeMnNi high entropy alloy

Abstract

The high-temperature deformation behavior of homogenized cast Al0.5CoCrFeMnNi with a coarse-grained face centered cubic (FCC) phase and a small amount of body centered cubic phase-dispersed within the FCC matrix grains was investigated using tensile creep and elongation tests at three temperatures of 1023, 1098 and 1173 K in a wide strain rate range between 10−8 and 10−1 s−1. As the strain rate increased, the strain rate regime associated with n = 3 (where n is the stress exponent) and n = 5 and power law breakdown (n > 7) appeared in sequence. As the temperature increased, the upper limit of the strain rate for n = 3 increased. The inverse primary creep behavior occurred and subgrain formation was not observed at the low strain rates and high temperatures associated with n = 3, strongly suggesting that solute drag creep is the rate-controlling deformation mechanism. Furthermore, the deformation mechanism of Al0.5CoCrFeMnNi was very similar to that of binary Al–Mg alloys known as typical class I solid solution alloys. The concept of breakaway stress from solute atmosphere could explain the transition of deformation mechanism from solute drag creep to dislocation climb creep at high strain rates.