Fabrication of composition-controlled TiNi shape memory wire using combustion synthesis process and the influence of Ni content on phase transformation behavior

TiNi intermetallic compounds were manufactured on an industrial scale using a combustion synthesis process that exploits the heat of formation between Ti and Ni. In this paper we investigate the influence of Ni content on the phase transformation temperature. The TiNi shape memory intermetallic compounds manufactured are homogeneous, show no gravity segregation, and have low oxygen content. Hot and cold plastic working can be carried out without difficulty. The martensitic (Ms) transformation temperatures of specimens that were solution-treated and heat-treated for aging fall rapidly with increased Ni content. However, the transformation temperature bottoms out at 51.4 at.% Ni and begins to rise again at 51.7 at.% Ni. The reason why the Ms temperature, etc., of the specimens heat-treated for aging rise more than for solution-treated specimens is that the Ti3Ni4 precipitates, causing the Ni content of the matrix to fall. The pattern of change in transformation temperature as a function of Ni content in the present experiment agrees with other researchers’ data in spite of the combustion synthesis process fundamentally different from the conventional melting process.© 2003 Elsevier Ltd. All rights reserved.