Microstructure and tensile properties of Cu[sbnd]Al alloys processed by ECAP and rolling at cryogenic temperature

Abstract

CuAl alloys with different stacking fault energy (SFE) were processed by equal channel angular pressing and rolling (ECAP + R) at cryogenic temperature with liquid nitrogen cooling. The effect of SFE on microstructure, effective grain size, dislocation density and tensile properties has been investigated. With decreasing of SFE during cryogenic ECAP, shear bands were developed to be step-shaped by cutting through high density of deformation twins, effective grain size reduces and dislocation density increases. Subsequently imposed to cryorolling, the lamellar thickness of twins and grain size is further reduced. Tensile strength increases with a decrease of SFE, and further enhanced after the additional rolling. The improvement of strength in CuAl alloys is attributed to the finer grains/twin thickness and the higher dislocations density. The maximum tensile strength of 871 MPa and uniform elongation of 4.3% in Cu7%Al is simultaneously achieved.