Experimental investigation and thermodynamic description of the constitution of the ternary system Cr-Si-C

The constitution of the ternary system Cr-Si-C is investigated using differ ential thermal analysis and X-ray diffractometry techniques. Eight invarian t reaction temperatures involving the liquid phase are determined, The crys tal structures and phase partitions observed for the subsolidus temperature region confirm literature data. Thermodynamic modeling, using a minimum of adjustable ternary parameters and assuming the binary high-temperature pha se, P-Cr5Si3, to be stabilized toward lower temperatures as ternary D8(8)-t ype Cr5Si3Cx, generally reproduces the measured temperatures within 10 K, T he calculated liquidus surface contains four ternary eutectics, three trans ition reactions, three degenerated reactions, and five (pseudobinary entect ics) maxima. The reaction scheme shows that no solid-phase reactions occur in the Cr-Si-C system at >1000 degrees C, except for the binary transition beta-Cr5Si3 <- -> alpha-Cr5Si3. The activity diagram along the section Cr-S iC at 1300 degrees C, computed from the optimized data set, agrees with the observed diffusion path.