Recrystallization Processes in a Ni-20%Cr Alloy Subjected to High-Pressure Torsion

Microstructure evolution during annealing of a Ni-20%Cr alloy subjected to high-pressure torsion (HPT) at ambient temperature was examined. It was shown that discontinuous static recrystallization (DSRX) occurs in non-uniform manner under subsequent annealing in the alloy strained to epsilon<4. The material strained to epsilon similar to 6 or higher exhibits continuous grain growth (GG) under subsequent annealing. It is attributed to the fact that HPT led to the formation of nanoscale grains with an average size of similar to 50 nm. Increasing fraction of these grains with strain leads to transition from DSRX to continuous GG under subsequent annealing. It was found that the main feature of recrystallization behavior of the Ni-20%Cr alloy subjected to HPT is simultaneous occurrence of short-range ordering and recrystallization processes under annealing conditions. As a result, despite the formation of recrystallized structure with an average grain size of similar to 340 nm after annealing at 600 degrees C (0.52 T-m), the material exhibits very high microhardness of 3.6 GPa.