Enhancing the high-temperature mechanical property and microstructure stability in Ti-4822 matrix composites via Ti/Al transition layer

This study synthesized and characterized the Ti-4822 matrix composites via Ti/Al transition layer introducing TiB and Ti2AlC, which was produced by spark plasma sintering. The grain size of composites decreased significantly from 221.5±5 μm to 61.2±5 μm with the increase of B4C content, mainly due to the pinning effect of in-situ generated primary TiB and Ti2AlC ceramic phases at grain boundaries, which limited the rapid grain growth of the matrix. The ultimate tensile strength and total fracture elongation of the alloy were 433.5 MPa and 13.3% at 800 °C, correspondingly. With 0.3 wt% addition of B4C, the composite exhibited superior strength (494.5 MPa) and ductility (22.5%) at the same tensile temperature. The reinforced strength of the composite was mainly attributed to the grain refinement and precipitation strengthing. In addition, the primary TiB and Ti2AlC were stapled at the grain boundary as the primary protective net, and the secondary TiB and Ti2AlC were stapled between the interlamellar as the secondary protective net, which significantly improved the microstructure stability of the composites at high temperature.