Deformation induced martensite and superelasticity in a beta-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 met astable 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 trea tment at a slightly lower temperature (850 degrees C) increases the stabili ty of the beta phase and the martensite thus becomes a strain-induced type. Decreasing the solution treatment temperature further (800 degrees C) lead s to a sufficiently stable beta phase so that no martensite is formed under tensile deformation and only slip is activated. These different ways of ac commodating deformation result in various mechanical responses. In particul ar, the stress-assisted martensite in this alloy is partly reversible under unloading, which produces significant superelasticity. (C) 2000 Elsevier S cience S.A. All rights reserved.