文摘
MAX phases in the (Crx,V1−x)n+1AlCn system were synthesized by reactive sintering or hot isostatic pressing of elemental powders at temperatures between 1400xA0;°C and 1600xA0;°C. For nxA0;=xA0;1, a complete range (0xA0;≤xA0;xxA0;≤xA0;1) of solid solutions was found; for nxA0;=xA0;2 and 3 the solubility ranges were 0.25xA0;≤xA0;xxA0;≤xA0;0.75 and 0xA0;≤xA0;xxA0;≤xA0;0.5, respectively. Powder X-ray diffraction revealed that the lattice parameters of all (Crx,V1−x)n+1AlCn solid solutions followed Vegard’s law. The thermal expansion coefficients of the various compounds were determined from Rietveld refinements of X-Ray patterns obtained at temperatures between ambient and 800xA0;°C. For the nxA0;=xA0;1 and 3 phases the thermal expansion coefficients were almost isotropic; those for the nxA0;=xA0;2, however, were quite anisotropic with the expansion along the a-axis being significantly larger than along the c-axis. As a general trend, vanadium rich compounds have smaller thermal expansion coefficients than their Cr-rich counterparts.