On the mechanism of superelasticity in Gum metal

The deformation mechanisms of the beta-Ti alloy, Gum metal, were investigated with the aid of in situ synchrotron X-ray diffraction (SXRD) and transmission electron microscopy (TEM). SXRD showed that Gum metal undergoes it reversible stress-induced martensitic (alpha '') phase transformation. Oxygen increases the resistance to shear by increasing C' and limits the extent of alpha '' growth. Prior deformation aids alpha '' formation of by providing nuclei, such as {112} < 111 > twins and stress-induced omega plates. The formation of twins and omega plates, both observed in TEM, are believed to be a result of a low G(111) in this alloy. Features similar to the giant faults seen previously were observed in TEM their formation is believed to be a result of {112} < 111 > shear. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved,