Synergistic effects of twin boundary and phase boundary for enhancing ultimate strength and ductility of lamellar TiAl single crystals

HG Xiang and WL Guo, INTERNATIONAL JOURNAL OF PLASTICITY, 150, 103197 (2022).

DOI: 10.1016/j.ijplas.2021.103197

The strength-ductility trade-off is a long-standing challenge in engineering and material sciences. The introductions of twin boundary or phase boundary in materials have been proven to be effective to tackle the difficulty, using different strength-ductility mechanisms. Here, we show that lamellar TiAl single crystals with both twin boundary and phase boundary exhibit strength and ductility synergy different from the existed mechanisms. The synergistic effects of twin boundary and phase boundary enhance the strength by 8.3% and the ductility by 24.7%, more effective than the enhancement by pure phase boundaries. The improvement is found to attribute to a distinctive multistage stress increasing caused by dislocation retractions. Meanwhile, the synergistic effect can be pronounced by increasing the twin boundary/phase boundary ratio. The dislocation retraction can be explained by the high image force from twin-phase boundary. Theoretical modelling indicates that such dislocation retraction can occur when the lamellar is thinner than 217 nm, showing a realistic route for promoting strength and ductility of TiAl single crystals.

Return to Publications page