A Study of Strain-Induced Phase Transformations in TiNi Alloy by Electric Resistance Method

Abstract

<p>It is generally recognized that the shape memory effect (SME) is associated the interaction of stress with thermoelastic martensitic transformation [1]. The phase transformations in TiNi alloy was reported to occur as three kinds of B2→R, B2→M, R→M phase transformations [2]. There are different views about premartensitic transformation in TiNi based alloys. Mwang et al [3] reported a transformation sequence in TiNiFe alloy that was the parent B2→Incommensurate I→Rhombohedra R→Martensite M. But many authors [2,4] reported that the premartensitic structure of TiNi alloy is rhombohedra. It is known that the electric resistance increase in the premartensitic transformation range was because of the R-phase taking affect. The electric resistance decrease below the temperature MS was because of the martensite occurence. It is not clear what occurred when the SME alloy is made a plastic deformation. Muang et al [5] was reported that in a TiNi alloy the new rhombohedral phase, perhaps, was induced by stress in the internal friction experiment. In this paper the phase transformation induced by the plastic deformation was studied by the electric resistance method.</p>