Transformation behavior of Ti-(45-x)Ni-5Cu-xCr (at%) (x = 0.5-2.0) shape memory alloys

Abstract

Transformation behavior and shape memory characteristics of Ti-(45-x)Ni-5Cu-xCr (x=0.5-2.0) alloys have been investigated by means of electrical resistivity measurements, differential scanning calorimetry, X-ray diffraction and thermal cycling tests under constant load. Two-stage B2-B19-B19' transformation occurred in Ti-(45-x)Ni-5Cu-xCr alloys. The B2-B19 transformation was separated clearly from the B19-B19' transformation in Ti-44.0Ni-5Cu-1.0Cr and Ti-43.5Ni-5Cu-1.5Cr alloys. A temperature range where the B19 martensite exists was expanded with increasing Cr content because decreasing rate of Ms (85 K/% Cr) was larger than that of Ms' (17 K/% Cr). Ti-(45-x)Ni-5Cu-xCr alloys were deformed in plastic manner with a fracture strain of 68% ~ 43% depending on Cr content. Substitution of Cr for Ni improves the critical stress for slip deformation in a Ti-45Ni-5Cu alloy due to solid solution hardening. ? 2011 KIEEME. All rights reserved.