Shape memory behavior of Ni-rich NiTi foam with different porosity percentages

Abstract

The shape memory properties of Ni_50.6Ti_49.4 alloy having porosity levels of 36%, 55%, and 60% such as recoverable and irrecoverable strain levels, transformation temperatures, and thermal hysteresis are determined from isobaric cooling–heating experiments. High recoverable strain up to 4.5% and almost no irrecoverable strain against up to 100 MPa of applied stress levels are observed due to the high strength of the sintered 36% porous Ni_50.6Ti_49.4 alloy. More interestingly, thermal hysteresis under constant stress levels for this sample is notably very low. Furthermore, as the porosity percentage increases from 36% to 55% and 60%, the recoverable strain levels under low constant stress levels increases. Additionally, since the strength of the 60% porous NiTi alloy decreases, it fractures at a relatively lower stress level.