Solidification behavior of TiB2-Ti2AlN reinforced TiAl composites with variation Al content

To address the inherent trade-off between strength and ductility in TiAl alloys, multi-component TiB₂-Ti₂AlN reinforced TiAl composite was designed by tailoring Al content and prepared using metallurgical techniques. The solidification behavior of TixAl2Cr2Nb-0.5BN composites were influenced by Al contents, exhibiting varied solidification path. An increase in Al content from 44 to 50 at.% leaded to a rise in the volume fraction of Ti₂AlN precipitates, shifting from 0.34 % to 2.05 %. Notably, the minimum lamellar colony size of 44 μm was produced with an Al content of 48 at.%. Simultaneously, both the γ-phase and the lamellar spacing underwent expansion as the Al content increased. A duplex microstructure was achieved at an Al content of 50 at.%. The Ti48Al2Cr2Nb-0.5BN composite exhibited an ultimate compressive strength of 2263 MPa, representing an enhancement of 47 % compared to the Ti44Al2Cr2Nb-0.5BN composite. Additionally, this composite displayed the highest compressive strain, marking an improvement of 115 %. The dominant fracture mechanisms of TiAl composites were revealed, including grain boundary fracture, crack deflection, inter-lamellar fracture, and the pull-out of reinforcing phases.