Parallel twinning during creep deformation in soft orientation PST crystal of TiAl alloy Original Research Article

Compression creep tests were conducted in the soft orientation PST TiAl crystals under the constant stress condition with applied stress of 100–316 MPa at 1150 K to investigate the effect of parallel twinning on creep deformation behavior. The effect of applied stress and strain on parallel twinning during creep deformation is quantitatively investigated. The generation of parallel twins reduced the average lamellar spacing during creep deformation. The critical resolved shear stress for nucleation of parallel twins was measured as 50 MPa. The activity of parallel twinning increased with increasing applied stress. The nucleation of parallel twinning finished at a strain less than 0.02. The lamellar refinement by parallel twinning did not change the creep rate of the PST crystal under the creep conditions studied. The effect of parallel twinning on creep behavior is discussed on the basis of microstructural investigation.