Effect of Accumulative Roll Bonding and Equal Channel Angular Rolling on Microstructural and Mechanical Properties of Cu–Al–Mn Shape Memory Alloys

Two Cu-based shape memory alloys, Cu–9.5Al–8.2Mn and Cu–8.3Al–8Mn (in wt%), were chosen for the present study and subjected to severe plastic deformation by accumulative roll bonding (ARB) and equal channel angular rolling (ECAR) processes, respectively. The effects of ARB and ECAR processes with subsequent post-deformation annealing on the transformation temperatures, microstructure and mechanical properties of these alloys were investigated. The ARB process was carried out at 600 °C, followed by post annealing at 700 °C for different lengths of time. The ECAR process was performed in 5 passes at room temperature, followed by post annealing at 890 °C for different lengths of time. Scanning electron microscopy studies revealed that the coexistence of bainitic and martensitic structures was the main reason for enhancement of mechanical properties of Cu–8.3Al–8Mn alloy. It also revealed that the enhancement of tensile properties of Cu–9.5Al–8.2Mn alloy could be directly attributed to the grain refinement induced by ARB and post deformation annealing. For both alloys, transformation temperatures reduced and selective growth of martensite variants occurred after post-deformation annealing.