In-situ formation and regulation of Ti2AlC particles with low aspect ratio and their influence mechanisms on microstructure and mechanical properties in Ti-46Al-8Nb-1.5Cr-xC alloy

To obtain a high volume fraction of Ti₂AlC particles with a low aspect ratio and to elucidate their formation mechanism, Ti-46Al-8Nb-1.5Cr-xC alloys were fabricated using vacuum arc melting. A systematic investigation was conducted on the lamellar colony size, Ti₂AlC particle content and morphology evolution, phase constituents, and mechanical properties, along with a discussion of the corresponding mechanisms. The results show that as the carbon content increases from 0.5 to 3.0 at.%, the B2 phase gradually decreases and eventually disappears, while the average lamellar colony size is refined from 97 to 39 μm. Simultaneously, the morphology of Ti₂AlC particles changes from initially elongated shapes to equiaxed shapes forms, with the aspect ratio decreasing from 9.33 to 3.28. The proportion of low-aspect-ratio Ti₂AlC particles increases from 4.1 to 77.8 %. The formed Ti₂AlC particles not only act as heterogeneous nucleation sites for the β phase but also impede the growth of the α phase, thereby providing the basis for lamellar colony refinement. The increased number of TiC particles, combined with the reduced surface energy difference between the (0001) basal plane and other crystallographic planes, jointly inhibited the growth of Ti₂AlC particles. In terms of mechanical properties, the compressive strength increases from 1491 to 2299 MPa, and the strain improves from 17.66 to 34.48 %. The enhancement in strength is mainly attributed to lamellar colony refinement and precipitation strengthening by Ti₂AlC particles. Moreover, the reduction of the B2 phase and the crack-arresting effect of Ti₂AlC particles contribute to the improved toughness of the alloy.