INVESTIGATIONS IN THE TERNARY-SYSTEMS V-SI-C AND TA-SI-C

Within a series of papers dealing with phase diagrams relevant to joining ceramics to metals the binary systems V-Si-C and Ta-Si-C are investigated. At 1000-degrees-C only one ternary phase, M5Si3C1-x(M=V, Ta) is observed in each system. V5Si3C1-x coexists with SiC, VC, V5Si3 and VSi2 thus dominating the isothermal section. In contrast, Ta5Si3Co.5 coexists with TaC, Ta2C, Ta2Si, Ta2Si3 and TaSi2 but not SIC, because TaC is the dominating phase in this system. Nevertheless,the thermochemical stabilities of the two ternary phases,as derived from the observed phase equilibria and thermochemical data of the binary boundary phases,turn out to be identical within the uncertainty limits of the method.