The uniazial compression was applied with a hot press apparatus for the partially sintered preforms with three chemical com positions, 3mol Y23Zr2 (TZ-3 Y), 6mol Y23Zr2 (TZ-6 Y), and 8mol Y23Zr2(TZ-8 Y). The change in size was measured after pressing. Obviously, the densification occurred below 1350 and superplastic defomation appeared mainly over 1350. The grain size at 1500 was 2m in TZ-8 Y in comparison with 0.4m in TZ-3 Y. TZ 6 Y and TZ-8 Y had a porosity of 5-15 because of the rapid grain

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... rowth. Consequently, small bending strengths in the range of 20-30kgf/mm2 were obtained. In TZ-3 Y, the compressive deformation gave a rapid increase in strength up to 140kgf/mm2. But the strength decreased above 1450, due to the formation of R-phase, by Kitano et al. (1987).