Microstructural evolution of Ag-0.20wt-%Mg-0.19wt-%Ni alloy in under-oxidized condition

The under-oxidized condition (insufficient internal oxidation) for Ag-0.20Mg-0.19Ni (in wt-%) alloy was conducted at 650°C for 2 h, and the microstructural evolution in the alloy was investigated. The average grain size of the oxidized region and the unoxidized region are 3.82 µm and 3.86 m, respectively. The results suggest that the oxides enriched at grain boundaries do not hinder grain growth in the under-oxidized condition. The hardness of the oxidized region increases significantly, while the hardness of the unoxidized region decreases due to recrystallization. Both the number and the distribution area of MgO precipitates at the grain boundaries are increased with the internal oxidation time. Additionally, small MgO precipitates merge to form larger oxide particles with the internal oxidation time.