Micromechanical analyses on bending of polysynthetically twinned single crystal of titanium aluminide

Abstract

Micromechanical bending analyses via CPFEM of polysynthetically twinned (PST) single crystal of TiAl composing of one α2-phase lamella and six γ–phase lamellae have been performed. The results have demonstrated that a decrease in the domain size aspect ratio λD/λL or an increase in the volume fraction of α2 phase fα2 have an effect of increasing the induced bending moment and consequently bending resistance under both bending modes of hogging and sagging. The similar variations in λD/λL and fα2 results in a decreasing trends of maximum tensile and compressive initial yield stresses (normal bending stresses), obtained through small strain beam theory. Results have also shown the effects of imposed constraints on the bending behavior; traction-free boundary conditions result in activation of prismatic slips instead of pyramidal slips in α2-phase, leading to a lower observed bending moment for the variables λD/λL and fα2 considered. A scaling law is proposed that relates bending moment to domain size aspect ratio and bending angle.