EFFECT OF A LIQUID-PHASE ON SUPERPLASTICITY OF 2-MOL-PERCENT-Y2O3-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTALS

A small addition of CuO to 2‐mol%‐Y2O3‐stabilized tetragonal zirconia polycrystals significantly enhances superplasticity by forming an amorhous grain‐boundary phase containing primarily Cu+, Y3+, Zr4+, and O2−. This phase apparently melts at around 1130°C, but it already provides a fast diffusion path even below the melting temperature. There are abrupt changes in stress exponent, activation energy, and grain size exponent across the melting temperature. Superplasticity is diffusion‐controlled below the melting temperature and is interfaced‐controlled above that. Copyright © 1990, Wiley Blackwell. All rights reserved