Deformation induced martensite and superelasticity in a β-metastable titanium alloy

This work investigates the formation of deformation induced martensite and shape-memory effects of water quenched P-rich microstructures of a beta metastable titanium alloy denominated beta-Cez (developed by the Cezus company). In highly beta metastable microstructures - solution treatments for 1 h at 920 (beta domain) or 860 degrees C (alpha+beta domain) - the beta phase transforms to a martensite that is stress-assisted in nature. Solution treatment at a slightly lower temperature (850 degrees C) increases the stability of the beta phase and the martensite thus becomes a strain-induced type. Decreasing the solution treatment temperature further (800 degrees C) leads to a sufficiently stable beta phase so that no martensite is formed under tensile deformation and only slip is activated. These different ways of accommodating deformation result in various mechanical responses. In particular, the stress-assisted martensite in this alloy is partly reversible under unloading, which produces significant superelasticity. (C) 2000 Elsevier Science S.A. All rights reserved.