Differential sintering of Al2O3/ZrO2–Ni composite, during pulse electric current sintering

Powder mixtures of Al2O3, ZrO2, Ni were sintered by pulse electric current sintering at 1300 °C with a heating rate of 200 °C/min or 130 °C/min. Large ZrO2–Ni agglomerates are formed within the Al2O3 matrix after sintering. Depending on the heating rate, these agglomerates formed networks within the matrix. The networks are heterogeneously distributed in the specimens prepared by the heating rate of 200 °C/min but homogeneously in the specimens prepared by the heating rate of 130 °C/min. The microstructure evolution of the specimen prepared by the heating rate of 200 °C/min indicates that the temperature at the edge of the specimen is higher than that at the center. The temperature difference is smaller for the specimen prepared by the heating rate of 130 °C/min. The small ZrO2 particles tend to associate with nickel melt to form ZrO2–Ni agglomerates. Then the ZrO2–Ni agglomerates are migrated by magnetic field that induced by the pulse electric current.