Creep behaviour and microstructural evolution of Al x CrMnFeCoNi high-entropy alloys

The creep deformation behaviour of thermo-mechanically treated Al x CrMnFeCoNi high-entropy alloys was investigated in the high-temperature range of 600–700°C. Compared with the Al-free CrMnFeCoNi alloy, the Al x CrMnFeCoNi alloys showed higher creep resistance under the same creep conditions due to strengthening contribution from elemental Al. The Al 0.4 CrMnFeCoNi alloy exhibited a stress-dependent transition from the low-stress region to high-stress region. The Al 0.6 CrMnFeCoNi alloy showed decreased creep resistance compared to the Al 0.4 CrMnFeCoNi alloy, which was ascribed to the higher activation volume and stacking-fault energy in the former alloy. Specifically, the intragranular formation of Cr-rich σ precipitation was widely found in the matrix grain among testing conditions, indicating a striking atomic diffusion process due to the limited entropic stabilisation in Al-containing CrMnFeCoNi alloys.