Alumina-spinel(NiAl2O4, CoAl2O4 solid solution)-metal(nickel, cobalt solid solution) composites were fabricated by partial reduction of spinel in carbon-bed and sintered with three different processes namely, pressureless, hot pressing, and spark plasma sintering (SPS). The microstructural features and mechanical properties of composites were investigated. The pressureless samples, SPS samples, and hot pressed samples reached > 91%, > 97% and > 98% theoretical density, respectively. The flexural strength of SPS, hot pressed, and pressureless samples were about 415 MPa, 367 MPa, and 247 MPa, respectively. Vickers Microhardness of SPS, hot pressed, and pressureless sintering were about 15.3, 14.5, and 10.98 GPa, respectively. The fracture toughness of SPS and hot pressed samples did not have a significant difference, and they were about 7.2 and 7.8 MPa.m1/2, repectively

Keywords: Alumina (Al2O3), Composite, Nickel, Cobalt, Pressureless, Spark plasma sintering (SPS), Hot Press, Mechanical properties.