Effect of Yttria on Interfacial Reactions Between Titanium Melt and Hot‐Pressed Yttria/Zirconia Composites at 1700°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°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 α‐Ti and β′‐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, α‐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 α‐Zr decreased with increasing Y 2 O 3 .