Change in Magnetic Susceptibility of Ti–Ni Shape Memory Alloys Associated with Martensitic Transformations

Abstract

The main phases (B2, R, B19, B19′ and Ti₃Ni₄) appearing in Ti–Ni-based shape memory alloys are band paramagnetism with magnetic susceptibility in the order of 10⁻⁸ m³/kg. All martensitic transformations in the cooling process (B2 → B19′, B2 → R, B2 → B19, R → B19′ and B19 → B19′) are associated with the decrease in magnetic susceptibility. This implies that all martensitic transformations in Ti–Ni-based shape memory alloys are associated with decrease in electronic density of states at Fermi energy. The change in magnetic susceptibility from the B2-phase is largest for the B2-B19′ transformation and smallest for the B2-R transformation.

Fig. 1 Temperature dependence of magnetic susceptibility of solution treated Ti–50Ni, Ti–51Ni and Ti–52Ni alloys. Ti–50Ni and Ti–51Ni exhibit the B2 → B19′ transformation, while Ti–52Ni does not exhibit martensitic transformation.