Effect of yttria on interfacial reactions between titanium melt and hot-pressed yttria/zirconia composites at 1700 degrees C

Abstract

Various Y(2)O(3)/ZrO(2) samples were fabricated by hot pressing, whereby Y(2)O(3) was mutually dissolved or reacted with ZrO(2) as a solid solution or Zr(3)Y(4)O(12). Hot-pressed samples were allowed to react with Ti melt at 1700 degrees C for 10 min in argon. Microstructural characterization was conducted using X-ray diffraction and analytical electron microscopy. The Y(2)O(3)/ZrO(2) samples became more stable with increasing Y(2)O(3) because Y(2)O(3) was hardly reacted and dissolved with Ti melt. The incorporation of more than 30 vol% Y(2)O(3) could effectively suppress the reactions in the Ti side, where only a very small amount of alpha-Ti and beta'-Ti was found. When ZrO(2) was dissolved into Ti on the zirconia side near the original interfaces, Y(2)O(3) reprecipitated in the samples containing 30%-70 vol% Y(2)O(3), because the solubility of Y(2)O(3) in Ti was very low. In the region far from the original interface, alpha-Zr, Y(2)O(3), and/or residual Zr(3)Y(4)O(12) were found in the samples containing more than 50 vol% Y(2)O(3) and the amount of alpha-Zr decreased with increasing Y(2)O(3).