A theory of the positive temperature dependence of yield stress in TiAl

Abstract

TiAl single crystals with the L1₀ structure show a positive temperature dependence of yield stress (PTYS) at intermediate temperatures as shown by our previous work similarly to Ni₃Al with the L1₂ structure. A strengthening mechanism for the PTYS is proposed, which is based on cross-slip and pinning of the 1/6 [112] or 1/6[121] Shockley partial from the {111) to the {110) or {011) plane, explaining the PTYS for the orientations where the ½[110]-type ordinary dislocations and ½[112]-type superdislocations operate as a primary slip system as well as the PTYS for the [101]-type superdislocations.