EBSD study on the effect of second phases and restoration mechanisms in hot deformed new Mn–Ni–Cr alloy

Abstract

Hot compression tests were performed on Mn–25Ni–5Cr at temperatures of 850–1000 °C and strain rates of 0.001–1 s−1. The flow curves at low strain rates were typical of dynamic recovery. However, at high strain rates, the flow curves were characterized by work hardening and slight flow softening proposing dynamic recrystallization. SEM-EDS observations showed that the microstructure at high temperatures is consisted of δ (bcc) and γ (fcc). The volume fraction of δ rises from zero at 850 °C to about 10% at 1000 °C. The EBSD observations revealed that dynamic recrystallization and extensive grain growth are the major phenomena at 850 °C. At higher temperatures, however, δ islands restrict the matrix grain growth and stimulate dynamic recrystallization. The accommodation of strain by δ islands caused extensive dynamic recrystallization inside the islands. Using the constitutive analysis the average value of activation energy was determined as 394.63 kJ/mol.