STABLE AND METASTABLE PHASE-RELATIONS IN THE SYSTEM ALUMINA-ZIRCONIA-YTTRIA

The Al2O3-ZrO2-Y2O3 system was studied in the range of temperatures 16 00-2800 degrees C by methods of X-ray analysis at 20 degrees C, petrog raphy, DTA in He at temperatures to 2500 degrees C, thermal analysis i n air using a solar furnace at temperatures to 3000 degrees C, and ele ctron microprobe X-ray analysis. The stable and metastable phase diagr ams were constructed. The liquidus and solidus projections, crystalliz ation paths for the alloys, and polythermal sections are presented in the article. The structure of the restricting systems defines the phas e equilibria in the ternary system. No ternary compounds were found. T he metastable phase relations were caused by the ambivalent behavior o f Y3Al5O12 during crystallization.