Shape memory properties of Ti-Nb-Mo biomedical alloys

Abstract

Mo is added to Ti-Nb alloys in order to enhance their superelasticity. The shape memory properties of Ti-(12-28)Nb-(0-4)Mo alloys are investigated in this paper. The Ti-27Nb, Ti-24Nb-1Mo, Ti-21-Nb-2Mo and Ti-18Nb-3Mo alloys exhibit the most stable superelasticity with a narrow stress hysteresis among Ti-Nb-Mo alloys with Mo contents of 0, 1,2 and 3 at.%, respectively. The ternary alloys reveal better superelasticity due to a higher critical stress for slip deformation and a larger transformation strain. A Ti-15Nb-4Mo alloy heat-treated at 973 K undergoes (2 1 1)< 1 1 1 >-type twinning during tensile testing. Twinning is suppressed in the alloy heat-treated at 923 K due to the precipitation of the a phase, allowing the alloy to deform via a martensitic transformation process. The Ti-15Nb-4Mo alloy exhibits stable superelasticity with a critical stress for slip deformation of 582 MPa and a total recovery strain of 3.5%. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.