The copper-matrix composites reinforced with oxides of Al

2

O

3

SiO

2

and MgO

were fabricated by powder metallurgy.The effects of volume fraction of reinforcements on the properties and microstructure of copper-matrix composites were investigated

and the enhancement effect and strengthening mechanism of the different oxide particles in copper matrix were also analyzed.The results show that the hardness of copper matrix composites is increased firstly and then reduced with the increase of reinforcement’s volume fraction.When the volume fraction of oxide particles reaches 2.5%

the hardness of Al

2

O

3

/Cu composite and MgO/Cu composites reach 94.4HB and 93.9HB

respectively.And the hardness of Al

2

O

3

/Cu composites and MgO/Cu composites are all higher than that of SiO

2

/Cu composite at the same volume fraction of oxide particles.Microstructure observation shows that the oxides are distributed uniformly and the grains are in alignment in the copper matrix composites in composites with low oxide volume fraction

and the particle reunite phenomenon occurs when the oxide volume fraction increases.The dispersed nanoscale oxide particles in copper matrix and dislocations after hot extrusion can improve mechanical properties of the composite together

which can pin in the crystal and grain boundary and hinder the dislocations movement.The main strengthening mechanisms of the copper matrix composites fabricated by powder metallurgy belong to dislocation strengthening and particle composite strengthening.