Creep Behavior of High‐Nb TiAl Alloy at 800–900 °C by Directional Solidification

Cold crucible directional solidification Ti44Al6Nb1.0Cr alloy is crept at 800–900 °C. Experimental results show that creep lifetime significantly decreases with the increasing creep temperature. When creeping at 900 °C under 130 MPa, the T_Q twinning is activated in lamellar structures. The T_Q twinning shows a strong dependency on temperature during creep under low creep‐stress and it can overcome α₂ lamellae and transfer into adjacent γ lamellae. The hardening by mechanical twinning and the softening by α₂ lamellar dissolution take place at different zones in lamellar structures and the strain incompatibility between hardening zone and softening zone promotes the microcracks to form in lamellar structures. The deformation characteristic of hard and soft lamellae is studied. Moreover, recrystallization γ phase formed in lamellar structures near colony boundary during creep at 900 °C accelerates the creep failure.