A Mechanism of the Positive Temperature Dependence of Yield Stress in Tial

Abstract

ABSTRACTThe positive temperature dependence of yield stress (PTYS) has been observed (Kawabata et al., Acta Metall., 33, 1355 (1985)) in TiAl single crystals in all orientations operating ordinary dislocations with the Burgers vector 1/2<110] and superdislocations with the Burgers vectors <101] and 1/2<112]. A mechanism for the PTYS is proposed, which is a cross-slip and pinning mechanism of Shockley partials with the Burgers vector 1/6<112] or/and 1/6<121]. The results of strain rate dependence of yield stress, K value dependence of critical resolved shear stress (CRSS) and transmission electron microscopy support the theory. Here, K value is the Schmid factor ratio of a Shockley partial on {101) or {110) plane and a perfect ordinary dislocation or a perfect superdislocation on {111) plane.