Refinement of Oxide Particles by Addition of Hf in Ni-0.5 mass%Al-1 mass%Y₂O₃ Alloys

Abstract

The effect of adding minor elements, such as Ti, Mg, Zr, Ca or Hf, on the size of oxide particles was investigated in Ni-based ODS alloy, Ni-0.5 mass%Al-1 mass%Y₂O₃. Among these elements, Hf is the most effective at refining the oxide particles, particularly at a concentration of 0.8 mass% Hf, as verified by TEM observation and hardness measurement. X-ray diffraction measurements indicate that the formation of Y₂Hf₂O₇ is responsible for the refinement of oxide particles. The Hf is also effective for a commercial superalloy of PM1000.