The tensile creep behavior of an equiatomic CoCrFeNiMn high-entropy alloy was systematically investigated over an intermediate temperature range (500–600 °C) and applied stress (140–400 MPa). The alloy exhibited a stress-dependent transition from a low-stress region (LSR-region I) to a high-stress region (HSR-region II). The LSR was characterized by a stress exponent of 5 to 6 and an average activation energy of 268 kJ mol⁻¹, whereas the HSR showed much higher corresponding values of 8.9–14 and 380 kJ mol⁻¹. Microstructural examinations on the deformed samples revealed remarkable dynamic recrystallization at higher stress levels. Dislocation jogging and tangling configurations were frequently observed in LSR and HSR at 550 and 600 °C, respectively. Moreover, dynamic precipitates identified as M₂₃C₆ or a Cr-rich σ phase were formed along grain boundaries in HSR. The diffusion-compensated strain rate versus modulus-compensated stress data analysis implied that the creep deformation in both stress regions was dominated by stress-assisted dislocation climb controlled by lattice diffusion. Nevertheless, the abnormally high stress exponents in HSR were ascribed to the coordinative contributions of dynamic recrystallization and dynamic precipitation. Simultaneously, the barriers imposed by these precipitates and severe initial deformation were referred to so as to increase the activation energy for creep deformation.

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.