Pressureless sintering and mechanical properties of titanium aluminum carbide

Titanium aluminum carbide (Ti2AlC) was synthesized and pressureless sintered. Phase-pure Ti2AlC powder was prepared by heating a powder mixture of Al:Ti:TiC = 1:1:0.75 (molar ratio) at 1300 °C for 4 h. The Ti2AlC compacts used for pressureless sintering contained 5 mass% Al2O3, Y2O3, MgO, CaO or TiO2, and were heated at 1400 °C for 2 h in Ar. The relative density of the Ti2AlC sample sintered without additive was 94.2%, while that of the sample with 5 mass% Al2O3 was 96.0%. Mechanical properties of all Ti2AlC samples were determined. Ti2AlC samples containing 5 mass% CaO showed the highest fracture strength (460 MPa) and Vickers hardness (5.8 GPa). All oxide additives resulted in reduced fracture toughness. Fracture toughness of the additive-free sintered Ti2AlC sample was 5.2 MPa·m1/2.