Effect of ageing on internal friction and elastic modulus of Ti-Nb alloys

This study aims to investigate the changes in internal friction and Young's modulus during ageing phase transformations in titanium-niobium binary alloys. Four types of alloys, which had niobium concentrations of 25, 30, 35, and 40 mass%, were used. These alloys were solution-treated at 1223 K, and aged at 423, 573, and 723 K. Although the highest Young's modulus of the quenched specimens was observed in the alpha + beta duplex structure of T30N and not the alpha martensite structure of T25N, it decreased with the amount of alpha martensite in other alloys. The internal friction of the quenched specimen decreased as the amount of the beta phase increased. The internal friction increased, but Young's modulus decreased during the processes of alpha -> beta reverse transformation and alpha precipitation during the ageing treatments. On the other hand, the internal friction decreased, but Young's modulus increased during the process of aged omega precipitation. In particular, the decreased internal friction of the alpha martensite structure of Ti-25Nb alloys aged at 723 K and the changes in both the internal friction and Young's modulus during the process of aged omega precipitation of the alpha + beta duplex structure were remarkable. (c) 2006 Elsevier B.V. All rights reserved.