Microstructure evolution, electrical conductivity and mechanical properties of dual-scale Cu5Zr/ZrB2 particulate reinforced copper matrix composites

Cu-0.3 wt% Zr alloys incorporated with varying ZrB2 levels were prepared by adjusting Zr/B addition rates via in-situ synthesis. Micro-scale ZrB2 particles formed through in-situ reactions between Zr and B in copper melt and nano-scale Cu5Zr precipitates formed upon aging treatment. The composites thus produced exhibited desired combination of mechanical properties and electrical conductivity. This paper investigates the effects of cryorolling and aging treatment on the microstructures and properties of the composites. Compared with traditional rolling process, the ultimate tensile strength of cryorolled Cu-0.3Zr–1ZrB2 composites increased from 541.9 MPa to 599.6 MPa without sacrificing too much electrical conductivity. The contributions of different strengthening mechanisms due to the dual-scale particles, twins, and dislocations were quantitatively calculated and the results showed good agreement with the experimentally measured data. Also revealed in this work is that the mechanical performance of Cu-0.3Zr-xZrB2 composites is relatively superior with respect to Cu-0.3Zr at 573 K, indicating that ZrB2 is in favor of enhancing the resistance to thermo-softening.