Oxide Particle Refinement in 4.5 mass%Al Ni-Based ODS Superalloys

Oxide particle refinement, which improves high temperature strength in Ni-based oxide dispersion strengthened (ODS) superalloys, was investigated by employing Hf addition during mechanical alloyed (MA) process. TEM micrographs show that 2 mass% Hf addition makes the smallest oxide particles and shortest separation in the base alloy (Ni–4.5 mass%Al–1 mass% Y2O3). Formation of Y2Hf2O7 is confirmed to be responsible for the oxide particle refinement with XRD analysis. By the calculation and comparison based on hardness and Orowan mechanism, the improvement of hardness by Hf addition attributes to the dispersion strengthening of oxide particles.