The quasi ternary system TiB2-CrB2-WB2 between 1900 and 2300°C

The quasi-ternary TiB2-CrB2-WB2 system has been studied up to 2300 degrees C by means of hot-pressing, SPS and pressureless dilatometry. Liquid phase is generated by two binary eutectics at the TiB2-WB2 edge at 2230 +/- 30 degrees C (e(1)) and at the CrB2-WB2 edge at 1965 degrees C (e(2)). A large homogeneity range of a (Ti,W,Cr)B-2 solid solution has been noticed. A new ternary gamma-phase emerges from a critical tie line between (W,Cr,Ti)(2)B-4 and alpha-(Ti,W,Cr)B-2 solid solution at 1950 degrees C, spreads slightly into both the WB2 and CrB2 direction and decomposes by the peritectic reaction P: gamma reversible arrow alpha-(Ti,Cr,W)B-2 + (W,Cr,Ti)(2)B-4 + Liquid at 2170 +/- 30 degrees C. gamma reacts with the CrB2-WB2-rich liquid according to the transition equilibrium T: delta-(Ti,Cr,W)B-2 + (W,Cr,Ti)(2)B-4 reversible arrow gamma + Liquid at 2050 degrees C. The gamma-phase is characterized by broad 001x-ray reflections which implies a layerwise accumulation and differentiation of Cr and W atoms in the basal plane of the AlB2-type structure.