Hetero-Deformation-Induced (HDI) Softening of a Harmonic Structure Designed CrMnFeCoNi Alloy Compact at Elevated Temperatures

The fabrication of a series of CrMnFeCoNi alloy compacts with homogeneous (Homo) and harmonic structure (HS) via powder metallurgy routes was followed by the subjection of these specimens to high-temperature compression tests at initial strain rates of 1.0×10-2 s-1, 1.0×10-3 s-1, and 1.0×10-4 s-1 at 1073 K and 1173 K. The HS compacts exhibited a well-developed ultra-fine grain (UFG) network structure, designated as the “Shell.” Consequently, the HS-designed specimen exhibited a pronounced reduction in flow stress in comparison to the homogeneous structure counterpart. Moreover, the homogeneous specimens exhibited a strain rate sensitivity value of less than 0.3, while the HS specimens demonstrated a strain rate sensitivity value greater than 0.3, with a value of 0.61 observed at 1173 K. This indicates that the HS specimens displayed pseudo-superplastic deformation behavior. This softening behavior can be attributed to the accumulation of dislocations in the shell region, which leads to dynamic recrystallization. This phenomenon can be understood as hetero-deformation-induced (HDI) softening.