Transformation behavior and shape memory characteristics of Ti-(45-x)Ni-5Cu-xV alloys

Abstract

Transformation behavior, shape memory characteristrics and superelasticity of Ti-(45-x)Ni-5Cu-xV(at%)(x=0.5-2.0) alloys were investigated. The B2-B19-B19' transformation occurs when V content was more than 1.0 at%, while the B2-B19' transformation occurred when V content was 0.5 at% in solution treated specimens. However, the B2-B19 and B19-B19' transformations were not separated clearly in the thermo-mechanically treated specimens. A temperature gap between Ms'(the B2-B19 transformation start temperature) and Ms(the B19-B19' transformation start temperature) increased from 8 K to 22 K with increasing V content from 1.0at % to 2.0 at% in solution treated specimens. One-stage elongation associated with the B2-B19' transformation occurred in a Ti-44.5Ni-5.0Cu-0.5V alloy, while two-stage elongation associated with the B2-B19-B19' transformation occurred in a Ti-43.0Ni-5.0Cu-2.0V alloy. The superelastic recovery ratio increased from 65.0 % to 86.1 % with increasing V content from 0.5 % to 2.0 % in solution treated specimens. The thermo-mechanically treated specimens showed the superelastic recovery ratio more than 95 %.