Low-temperature synthesis and characterization of Ti2AlC/TiAl in situ composites via a reaction Hot-Pressing Process in the Ti3AlC2-Ti-Al system

Ti2AlC/TiAl in situ composites were fabricated via a reaction Hot-Pressing Process using Ti3AlC2, Ti, and Al powders as initial materials. The effect of Ti2AlC content on the phases and microstructure of the as-sintered composites was investigated by XRD and SEM. The mechanical properties such as Vickers hardness, flexural strength and fracture toughness of the as-sintered composites were also tested. The products consisted of Ti2AlC, γ-TiAl and β2-Ti3Al as the major phases. Ti2AlC reinforcements were mainly distributed in the grain boundaries, resulting in obvious γ+β2 grain refinement. With increasing Ti3AlC2 content (up to 5 wt%), the Vickers hardness, flexural strength and fracture toughness of the as-sintered composite reached the maximum values of 3.7 GPa, 651.5 MPa, and 10.89 MPa·m1/2, respectively. Analysis of fracture surface and crack propagation paths indicated that crack deflection and crack bridging of the in situ precipitated Ti2AlC phases obtained by decomposing Ti3AlC2 were the main reasons for the observed composite toughening.