Role of grain boundary sliding in creep of FCC complex solid solutions

Abstract The present study reports on creep in two polycrystalline variants of FCC compositionally complex solid solutions, quinary CrMnFeCoNi (A5), and quaternary CrFeCoNi (A4). Tensile and compression creep experiments were performed at three temperatures, 873, 973 and 1073 K, and a range of applied stress. Apparent creep activation energies measured for the alloy A5 varied between 220 and 262 kJ mol⁻¹, which are systematically lower than activation energies reported for bulk diffusion of any of the five alloy constituents, indicating that grain boundary diffusion contributes to the temperature dependence of creep rate. Based on microstructural investigations, we provide conclusive proof for the occurrence of grain boundary sliding (GBS) at 973 and 873 K in the A4 alloy. A statistically relevant assessment of the GBS sliding parameters after creep of A4 at 873 K showed that up to about 60% of the total accumulated strain in early creep can be attributed to the GBS mechanism.