Microstructural Evolution of Oxide and Nitride Dispersed Nickel-Based Alloy Powders

The microstructural evolution of oxide and nitride dispersed nickel-based mechanical alloyed (MA) powders was investigated using in situ characterization methods, including high-temperature X-ray diffraction and transmission electron microscope (TEM). MA powders strengthened by Si₃N₄ and Er₂O₃ exhibited different behaviors. The added Si₃N₄ particles were not dissolved during the MA process, resulting in faster strain recovery and grain coarsening in the MA powders. In contrast, the Er₂O₃ particles were dissolved into the matrix during the MA process. Also, precipitation of Er₂Ti₂O₇ particles with an average size of 10 nm was observed by in situ TEM. The precipitation of nanoparticles was related to strain recovery and grain growth, as both reduced the solubility of solute atoms in the matrix. The in situ TEM observation results provide direct experimental evidence for the dissolution–precipitation mechanism in nickel-based MA powders.