Phase transformation behaviors and mechanical properties of Ti50Ni49Fe1 alloy with severe plastic deformation

Abstract

In this work, transformation behaviors and mechanical properties of cold-rolled shape memory alloy Ti50Ni49Fe1 by severe plastic deformation (SPD) were intensively investigated. The phase transformation behaviors, phase analysis, and microstructures were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM), respectively. Tensile testing was performed to analyze the effect of SPD on the mechanical properties and shape memory of Ti50Ni49Fe1 alloy. When the thickness reduction is beyond 30 %, the martensitic transformation is suppressed. After cold-rolling, the alloy is mainly composed of B2 parent phases with some stress-induced martensitic B19′ phases, and high density of dislocations are generated and the grains are obviously refined. The yield stress σ b significantly raises from 618 MPa of 0 % cold rolling to 1,338 MPa of 50 % SPD. Shape-memory effect increases from 6.5 % without cold rolling to 8.5 % after 30 % SPD, ascribed to the induced defects in cold rolling. Those results indicate that Ti50Ni49Fe1 alloy has improved mechanical properties and potential commercial applications after SPD.