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 and. 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.