Cu-based shape memory powder preparation using the mechanical alloying technique

Abstract

Shape memory powders with nominal compositions of Cu-25.5at.%Zn-5.5at.%Al and Cu-21.1at.%Zn-11.2at.%Al have been prepared starting from commercial powders of Cu84Zn16, Cu70Zn30 and Al using the mechanical alloying (MA) technique. The experimental results show that the microhardness of the mechanically alloyed powders indicates a steady state in which the increase in microhardness due to plastic deformation and the decrease in microhardness due to kinetic annealing have reached a balance. The MA process can still be continued efficiently after the microhardness reaches saturation point. Four stages in the formation of shape memory alloy powder have been identified: the formation of a laminated structure formation, the deformation of the laminated structure, the disappearance of the laminated structure and the formation of alloyed powders. Both X-ray and microstructure data using backscattered electron studies showed that the formation of shape memory powders can be obtained after 7.2 ks milling for 300 rev min −1 using a planetary ball mill.