Low-temperature superplasticity in a Cu–Zn–Sn alloy processed by severe plastic deformation

A copper alloy containing ∼38% Zn and ∼3% Sn was subjected to severe plastic deformation at a temperature of 400°C using the procedure of equal-channel angular pressing (ECAP). The microstructures produced by ECAP were relatively heterogeneous with areas of both recrystallized and unrecrystallized grains. Within the recrystallized areas, the average grain size was ∼1.5μm. Tensile testing after ECAP revealed the occurrence of superplasticity with elongations up to ∼900%. Superplastic ductilities were recorded at temperatures as low as 300°C corresponding to an homologous temperature of ∼0.51Tm, where Tm is the absolute melting temperature of the alloy. These results demonstrate the potential for achieving low temperature superplasticity in this alloy through ECAP. As in conventional superplastic Cu-based alloys, specimens failed because of the development of internal cavities.