Optimization of microstructure and high-temperature mechanical properties of Ti4822/Ti2AlC composites through multiple solution-aging treatments

In this paper, a Ti-48Al-2Cr-2Nb (Ti4822, at%) based composite with uniformly distributed Ti2AlC nano-micro precipitates was prepared by powder metallurgy followed by a multiple solution-aging treatment. Multiple solution treatments eliminated the equiaxial gamma grains in the sintered composites and refined the coarse-grained primary Ti2AlC phases, resulting in a fully lamellar microstructure with fine Ti2AlC precipitates embedded between the alpha(2)/gamma lamellae. The high-temperature ultimate tensile strength of the heat-treated Ti4822/Ti2AlC composites reached 543 MPa at 800 degree celsius, and the elongation was 7.7 %, increased by 9.7 % and 0.8 % correspondingly compared to that of the sintered composite. The enhancement of the properties of Ti4822/Ti2AlC composite in the heat-treated state was due to the elimination of gamma grains in the microstructure to transform the full lamellar microstructure on the one hand, and the refinement and dispersion of agglomerated Ti2AlC precipitates on the other hand. This study provided a valuable reference for the refinement and dispersion of the second phase in TiAl composites.