In-situ observation of microstructure evolution and improvement of distribution of reinforcing particles to reveal dual-enhancement mechanisms of strength and plasticity for Ti48Al2Cr2Nb3C alloy

To achieve a more uniform distribution of the reinforcing particle and then refine them, ultrasonic treatment (UT) performs in the liquid-solid two-phase region for a certain time of Ti48Al2Cr2Nb3C alloys. The influence of uniformly distributed reinforcing particle on the microstructure evolution process is revealed through in-situ observation and the mechanism of simultaneous improvement of strength and plasticity is revealed. Results show that UT effectively eliminates the B2 phase by facilitating solute diffusion. UT successfully disperses Ti₂AlC agglomerations and suppresses the formation of the network γ phase. The capillary and cavitation effects induced by UT contribute to the uniform distribution of Ti₂AlC, leading to a reduction in Al enrichment between Ti₂AlC clusters and subsequent elimination of the network γ phase. In the as-cast alloy, the presence of extensive dislocations near Ti₂AlC is attributed to melt shrinkage during solidification. A significant number of nano-twins are observed in the vicinity of Ti₂AlC after UT. This transformation is facilitated by the generation of Frank-Read sources induced by UT, which promote dislocation slip and twin formation. The compressive strength and strain of Ti48Al2Cr2Nb3C exhibit notable enhancements, increasing from 2088.7 MPa to 27.6% to 2422.4 MPa and 33.0%, respectively. The uniform distribution of Ti₂AlC effectively mitigates stress concentration-induced particle breakage, while the presence of twins provides protection against dislocation-induced damage. These improvements enhance the load-bearing capacity of Ti₂AlC, thereby improving the mechanical properties of Ti48Al2Cr2Nb3C alloy.