Strengthening in gradient TiAl alloys

Gradient structure is emerging as an effective strategy to fabricate metals with remarkable mechanical performance, but have not been verified in intermetallic compounds for high-temperature applications. Through experiments and atomic simulations, we show that a typical intermetallic TiAl alloy with gradient structure has a significant strengthening effect both at room temperature and high temperatures. The room-temperature compressive strength of TiAl alloys with gradient grain obtained by additive manufacturing is 2.57 GPa, which is ∼2.7 times as strong as that with equiaxed grain. The strengthening effect is attributed to more sessile dislocations in gradient structure caused by the intersections of multiple slip systems in gradient grain. More importantly, the strengthening effect is still effective at high temperatures and the compressive strength is 1.28 GPa at 750 °C. The simulation results show that this strengthening effect is due to the increased Hirth dislocation at high temperatures. This study expands the applications of TiAl alloys for load-bearing structures and provides a new strategy for improving the strength of intermetallic compounds at both room temperature and high temperatures.