Mechanical properties of the R-phase and the commensurate phase under [111] tensile stress in iron-doped titanium-nickel alloys

Abstract

We have studied deformation behavior of two kinds of iron-doped Ti-Ni shape memory alloys under tensile stress applied in the [111] direction. One is Ti-46Ni-4Fe (at%) alloy which transforms to the R-phase and the other is Ti-44Ni-6Fe (at%) alloy which transforms to the commensurate phase (C-phase) in the cooling process. The stress-strain curve measured in the R-phase region shows a residual strain due to rearrangement of variants while that measured in the C-phase shows a pseudoelastic behavior characteristic to stress-induced martensitic transformations. The strain-temperature curve measured under constant stress shows an obvious transformation strain associated with the transformation to the R-phase, while a bend point appears associated with the transformation to the C-phase.