Effect of M-site element on the interaction of M2AlC and Ag and the induced properties of Ag/M2AlC composites

The deintercalation of weakly bonded A element affects the microstructure and properties of MAX phases and their reinforced composites. In this work, the effect of M-site element on the interaction of Al-containing M2AlC (M = V, Cr) phase and Ag, and the induced properties of Ag/M2AlC electrical contact materials (ECMs) were investigated. Though Ag and Al are soluble to each other and can form intermetallics, the variation of M element significantly affected the vacancy formation of Al, and thereby the interfacial reaction of Ag/M2AlC. The difficult formation of Al vacancy in V2AlC contributed to no obvious interfacial reaction in Ag/V2AlC. But the easy deintercalation of Al atoms in Cr2AlC led to their massive replacement by Ag, which generated Ag nano-twins and Cr3C2 with the same crystallographic relationship in one original Cr2AlC, and Cr7C3 and Ag3Al as well. Due to the distinct interactions, the resistivities of Ag/V2AlC and Ag/Cr2AlC increased by roughly 1 and 5 times after sintering, respectively. The low resistivity and proper hardness of the sintered Ag/V2AlC, which were very close to those of the “all-purpose” commercial Ag/CdO, contributed to its superior arc erosion resistance.