Al2O3-Cu composites offer a promising combination of high hardness, thermal stability, and electrical conductivity. In this study, Al2O3-Cu composites containing 2.5 vol.% Cu were produced by uniaxial pressing at 100 MPa, followed by free sintering in a reducing atmosphere (95% Ar/5 % H₂). Sintering was performed at 1200 °C, 1250 °C, 1300 °C, and 1400 °C for 2 h to evaluate the influence of temperature on densification, microstructure, and mechanical properties. Phase analysis confirmed the presence of only corundum Al2O3 and metallic Cu, independent of sintering temperature. Relative density increased strongly with temperature, from 78.65% at 1200 °C to 96.99% at 1400 °C. Microstructural observations revealed significant copper migration at 1400 °C, leading to irregular Cu agglomerates, local depletion of the metallic phase, and the encapsulation of Al2O3 grains through non-wetting liquid-phase sintering. The composites sintered at 1400 °C exhibited an average hardness of 13.6 ± 1.5 GPa and an indentation fracture toughness KIC of 4.94 ± 0.85 MPa·m0.5. Fracture behavior was dominated by intergranular cracking and crack deflection at weak Al2O3-Cu interfaces. The results demonstrate that although high densification can be achieved without external pressure, uncontrolled copper migration remains a key limitation of pressureless sintering in Al2O3-Cu composites.