Processing and microstructure of TiNi SMA strips prepared by cold roll-bonding and annealing of multilayer

The preparation of TiNi SMA thin strip via cold roll-bonding and subsequent annealing treatment of pure Ti/Ni multilayer has been studied. The relationships between processing variables and microstructure formed based on the proposed method have been investigated by OM, SEM/EDS and XRD detections. It shows that the Ti/Ni multilayer with reduction of 97% can be possibly obtained by cold rolling of initially hot-press bonded pure Ti and Ni foils. Within the high thickness reduction of the multilayer, the TiNi phase is easily formed at relatively low annealing temperature and short annealing time. DSC measurement for the prepared TiNi strip have shown a good B2 to B19′ transformation behaviour and M_s at around 60 °C, transition hysteresis of about 30 °C and transition enthalpy of average 24 J/g, which is similar to those by the conventional ingot-metallurgy method.