In-situ reaction synthesis and mechanical properties of quaternary MAX phase (Cr2/3Ti1/3)3AlC2

Bulk quaternary MAX phase (Cr2/3Ti1/3)3AlC2 was synthesized by in-situ reaction/hot pressing method using Cr, Ti, Al, and C powders as starting materials. The involved reaction routes during hot-pressing were determined according to XRD and SEM/EDS analysis results. The possible chemical reactions involved during hot pressing process were proposed. It was revealed that the desired (Cr2/3Ti1/3)3AlC2 was formed via the reaction between intermediate products of ternary MAX Cr2AlC and carbide TiC, providing another path for the preparation of high order MAX phase. Tests of mechanical properties suggested that the Vickers hardness of (Cr2/3Ti1/3)3AlC2 was 5.6 GPa, higher than that of the ternary MAX phase Ti3AlC2. Its flexural and compressive strength were determined to be 493 MPa and 1407 MPa at room temperature, respectively. Flexural strength maintained a relatively high level of 424 MPa up to 1000 °C, about 90% of that at room temperature. The dependence of elastic modulus on increasing temperatures exhibited similar tendency to that of flexural strength. The as-synthesized (Cr2/3Ti1/3)3AlC2, a unique quaternary layered nano-laminated carbide, was a promising high temperature structural material with its attractively comprehensive properties.