Transformation behavior and shape memory characteristics of thermo-mechanically treated Ti-(45-x)Ni-5Cu-xV (at%) alloys

Abstract

Transformation behavior, shape memory characteristics and superelasticity of thermo-mechanically treated Ti-(45-x)Ni-5Cu-xV (at%) (x = 0.5-2.0) alloys were investigated by means of differential scanning calorimetry, transmission electron microscopy, X-ray diffractions, thermal cycling tests under constant load and tensile tests. The B2-B19' transformation occurred when V content was 0.5 at%, above which the B2-B19-B19' transformation occurred. The B2-B19 transformation was not separated clearly from the B19-B19' transformation. Thermo-mechanically treated Ti-(45-x)Ni-5Cu-xV alloys showed perfect shape memory effect and transformation hysteresis(Delta T) of Ti-43.5Ni-5.0Cu-1.5V and Ti-43.0Ni-5.0Cu-2.0V alloys was about 9 K which was much smaller than that of a Ti-44.5Ni-5.0Cu-0.5V alloy(23.3 K). More than 90% of superelastic recovery ratio was observed in all specimens and transformation hysteresis (Delta sigma) of a Ti-44.5Ni-5.0Cu-0.5V alloy was about 70 MPa, which was much larger than that of a Ti-43.0Ni-5.0Cu-2.0V alloy (35 MPa). (C) 2012 Elsevier Ltd. All rights reserved.