The Influence of Wire Drawing Parameters On the Martensitic Transformation Temperature of NiTi SMA

The NiTi shape memory alloys have a considerable range of thermal and mechanical properties providing a wide range of potential applications. However, these properties should be adjusted to each application. This work is focused on the influence of the wire drawing parameters (area reduction per pass and included die angle 2α) on the martensitic transformations temperatures of a near equitatomic Ni-50.04at%Ti shape memory alloy. The mechanical forming resulted in wires with distinct strain profiles that were partially recrystallized at 500°C per 15 min. The behavior of final wires was investigated by DSC, microhardness measurement and optical metallography. At same chemical composition, cold work and heat treatment, but varying the 2α was possible to change the reverse peak martensitic transformation temperature up to 7.1°C.