Crack micromechanisms in cycled shape memory alloys

Shape memory alloys are more and more used in many industrial, medical and automotive fields due to the ability to recover the initial shape after external loads producing high deformations thanks to the variations of their microstructure due to thermal or mechanical causes. Up to now, many models have been developed in order to describe the mechanical behaviour of SMA but most of them don’t take into account the real microstructure. In this work a traditional equiatomic NiTi SMA has been investigated both in terms of microstructure evaluation and in terms of mechanical cycling behaviour up to degratate the memory ability, obtained at around 100 cycles. The cycling behaviour has been investigated and a model has been proposed to predict the mechanical behaviour and the ability to recover the initial microstructure. The damaged alloy has been investigated in terms of surface fracture analysis obtained by traditional traction tests in order to investigate the main crack micromechanisms.