Formation of MAX solid solutions (Ti,V)2AlC and (Cr,V)2AlC with Al2O3 addition by SHS involving aluminothermic reduction

MAX solid solutions (Ti,V)2AlC and (Cr,V)2AlC with Al2O3 addition were produced by solid state combustion involving aluminothermic reduction in the mode of self-propagating high-temperature synthesis (SHS). Starting materials included TiO2/V2O5/Al/Al4C3 and Cr2O3/V2O5/Al/Al4C3 powder mixtures. Attempts were made to attain (Ti1−xVx)2AlC and (Cr1−yVy)2AlC with the V content in terms of x and y from 0.1 to 0.7. Combustion exothermicity was increased by increasing V2O5 for the yield of a higher proportion of V at the substitution site, which not only increased the combustion temperature and reaction front velocity, but also facilitated the evolution of solid solutions. Due to insufficient reaction exothermicity, (Ti1−xVx)2AlC/Al2O3 in situ composites were only produced under x≥0.4. On the other hand, the formation of (Cr1−yVy)2AlC/Al2O3 was achieved with y from 0.1 to 0.7, because reduction of Cr2O3 is more energetic than that of TiO2. The laminated microstructure characteristic of the MAX ternary carbide was observed for both Al2O3-added (Ti,V)2AlC and (Cr,V)2AlC composites synthesized in this study.