Improvement of microstructure and mechanical properties of Ti42Al6Nb2.6C alloy through Er doping and in-situ formation of Er2O3 particles

The improvement of the morphology and distribution of ceramic particles is a crucial aspect in enhancing the high-temperature strength and service temperature of TiAl-based composites. In this study, the Er element was successfully used to modify the morphology of the Ti2AlC reinforcing phase and improve room-temperature and high-temperature mechanical properties of the alloy. Results show that as the Er content increases from 0.04at.% to 0.08at.%, in-situ Er2O3 particles are distributed at the surface of Ti2AlC reinforcing phase and within the lamellar colony. Both the lamellar colony and Ti2AlC reinforcing phase are significantly refined. The orientation relationship between Er2O3 and Ti2AlC is $$\left\{111\right\}_{\rm{Er}_2{\rm{O}_3}}//\left\{0001\right\}_{\rm{Ti}_2AlC}$$ and $$\left\{110\right\}_{\rm{Er}_2{\rm{O}_3}}//\left\{11{\bar2}1\right\}_{\rm{Ti}_2AlC}$$ . The higher surface energy of Ti2AlC and the favorable orientation relationship allow the Er2O3 particles to nucleate on the Ti2AlC reinforcing surface. As a result, the growth of Ti2AlC is restricted by the fine Er2O3 particles, preventing its uncontrolled expansion and ultimately leading to the formation of fine, short rod-like structures. The fine Er2O3 and Ti2AlC act as nucleation sites for β grains, which is fundamental for obtaining fine lamellar colony. The Ti42Al6Nb2.6C0.08Er alloy exhibits superior room-temperature compressive properties with a compressive strength of 2,106 MPa and a compressive strain of 26.8%. The high-temperature compressive properties also demonstrate a great balance between strength and plasticity. The improvement in compressive properties are attributed to significant changes in microstructures, including the notable refinement of the lamellar colony, precipitation of Er2O3 particles, load transfer effect of the refined Ti2AlC reinforcing phase, and solid solution strengthening of Er solutes.