DSC study of the effect of aging temperature on the reverse martensitic transformation in porous Ni-rich NiTi shape memory alloy fabricated by combustion synthesis

The effect of aging temperature on the reverse martensitic transformation in the SHS-synthesized porous Ni-rich NiTi SMA after solution treated at 1050 °C for 4 h is investigated using differential scanning calorimeter (DSC) and discussed. The type of reverse martensitic transformation changes from one step B19′→B2 (after solution treated) through two steps B19′→R→B2 (after aged at 400, 450 and 475 °C) back to one step B19′→B2 (after aged at 500 °C). Both the austenite finish temperature (Af) and the peak temperature corresponding to the transformation of R→B2 decrease with the rise of the aging temperature. The experimental results also indicate that shape memory properties of porous NiTi SMA fabricated by SHS can be improved by optimizing the aging technology.