Microstructural characterization of Al2O3–Ni composites prepared by electroless deposition

Al2O3–Ni composites were prepared by pressureless sintering using Ni-coated Al2O3 powders produced by electroless deposition. After deposition, most of Al2O3 powders were coated with Ni layer 20-nm thick but some of the nano-sized Ni particles also were attached to the Al2O3 powders. Microcracks and reaction compounds were not observed at the interfaces between the Al2O3 and Ni phases after pressureless sintering. The Al2O3–Ni composite was comprised of Al2O3, Ni and Ni3P phases. A large number of dislocations were observed in the Ni phase due to the mismatch of thermal expansion coefficients (TEC) between Al2O3 and Ni phases. The main fracture mode showed a mixed type with intergranular and transgranular modes having some roughness. The fracture toughness was increased due to the plastic deformation mechanism of the Ni phase in the Al2O3 matrix.