Investigation of thermal stability of the structure and properties of ultra-fine-grained copper alloys obtained by ECAP

Abstract

The paper describes the results of experimental studies of the effect of small chromium additives on the temperature of recrystallization (TR) of ultrafine-grained (UFG) copper obtained by equal channel angular pressing. Our investigation shows that the process of recrystallization in UFG CuCr copper alloys has a three-stage character - anomalous grain growth at annealing temperatures not exceeding the temperature of chromium particles(Tann<T1), “fixation” of grain boundaries by the released particles (T1⩽Tann<T2), and regular grain growth at higher temperatures (Tann⩾T2), when grain boundaries “detach” from particles of the second stage. It also shows that an increase in the chromium concentration in UFG copper by 0.3-0.5wt.% leads to a decrease in the temperature of the onset of the migration of grain boundaries T1 in the UFG copper by 40-60°C and an increase in temperature T2 to ∼ 400°C. We discovered that low-temperature pre-recrystallization annealing contributes to an increase in the thermal stability of the mechanical properties of CuCr alloys.