Fabrication, interfacial characteristics and strengthening mechanisms of ZrB2 microparticles reinforced Cu composites prepared by hot-pressed sintering

1-9 wt% of ZrB2 particles are added to Cu to produce ZrB2/Cu composites by a hot-pressed sintering process. Microstructures, mechanical and electrical properties of the prepared ZrB2/Cu composites are systematically investigated. The results indicated that the relative density and electrical conductivity of the composites decrease with increasing ZrB2 content. However, the microhardness reaches a maximum value of 100.8 HV0.2 as ZrB2 content increases to 7 wt % and then decreases when ZrB2 content further increases. TEM study reveals that the hexagonal ZrB2 crystals in size of several micrometers are well embedded in Cu matrix. The interfacial zone consists of both sharp interfaces and amorphous transition layer. Grain refinement strengthening, Orowan strengthening and coefficients of thermal expansion mismatch strengthening contribute to the increment of microhardness and reduce the electrical conductivity.