Microstructure manipulation and strengthening mechanism of TiAl composites reinforced by Cr solid solution and in-situ nanometer-sized TiB2 particles

TiAl composites reinforced with 4 vol% nanometer-sized TiB2 particles and different contents of Cr were successfully prepared using fast hot pressing sintering. This process led to the simultaneous realization of in situ nanometer-sized TiB2 particle generation, a Cr solid solution, and the densification of the composite in one step. The nanometer-sized TiB2 particles were found to have excellent interface bonding with the TiAl matrix. Moreover, the generation of nanometer-sized TiB2 particles and the addition of Cr effectively reduced the grain size of TiAl composites by inhibiting the movement of grain boundaries. The average grain size of the 4 vol% TiB2/TiAl-3 at.% Cr composite was reduced by 86.4% relative to that of TiAl. At the same time, the yield strength (1121 MPa), ultimate compressive strength (2188 MPa), and product of strength and strain (25.93 GPa•%) of the 4 vol% TiB2/TiAl-3 at.% Cr composite increased by 58.3%, 24.7%, and 23.1%, respectively. The significant improvement in the performance is attributable to the synergistic effects of grain refinement strengthening, thermal mismatch strengthening, Orowan strengthening, and solid-solution strengthening.