High-Temperature Synthesis of Composite Materials Based on MAX Phases in the Cr–Mn–Al–C System

High-temperature synthesis of cast composite materials in the Cr–Mn–Al–C system with various ratios between the Cr 2 AlC MAX phase and chromium and manganese aluminides and carbides was studied. Experiments were performed in a universal 3-L reactor under argon pressure Р = 5 MPa. Mixtures of powders of chromium(III) and manganese(II, IV) oxides and calcium peroxide with aluminum (ASD-I) and carbon were used as a charge. The synthesis features and the phase composition and microstructure of the target products are significantly influenced by the reactant ratio in the charge. At the stoichiometric ratio of the components corresponding to the Cr 2 AlC phase, a cast composite material consisting of the Cr 2 AlC MAX phase, chromium carbides Cr 7 C 3 and Cr 3 C 2 , and chromium aluminide Cr 5 Al 8 is formed. In the course of combustion of the charge with the component ratio corresponding to the Mn 2 AlC phase, a cast composite material consisting of manganese carbides (Mn 3 AlC, Mn 0.545 Al 0.42 C 0.035 ) and aluminide (MnAl) is formed. When these compositions are combined in an 0.75 : 0.25 ratio, the final product is a composite material consisting of a solid solution based on the Cr 2 AlC MAX phase, manganese carbides (Mn 3 AlC), and chromium aluminides (Cr 2 Al). When these compositions are combined in an 0.5 : 0.5 ratio, the final product is a composite material consisting of the manganese-doped Cr 2 AlC MAX phase and of manganese (Mn 14 Al 86 , Mn 22.5 Al 77.5 ) and chromium (Cr 5 Al 8 ) aluminides. The final products were characterized by X-ray diffraction and local microstructural analysis.