Microstructures and properties of hybrid copper matrix composites reinforced by TiB whiskers and TiB2 particles

Hybrid copper matrix composites reinforced by TiB whiskers and TiB2 particles were fabricated by in situ mixing casting in combination with rolling and annealing. During turbulent mixing and copper mold casting processes, the in situ reactions carried out completely, and the macrosegregation of reinforcements in the composites was overcome efficiently. By controlling the rolling and annealing parameters, unfavorable casting defects, including chain-type reinforcement clusters and shrinkage porosities that formed during the end stage of solidification, were eliminated. Accordingly, the uniform distribution of hybrid reinforcements in the as-annealed composites provided good comprehensive performance. Compared to the 2.6 wt% TiB2p/Cu composite, the (1.0 wt% TiB2p-0.9 wt% TiBw)/Cu hybrid composite exhibited both higher strength (492 MPa) and higher electrical conductivity (85.5% International Annealed Copper Standard). Therefore, the hybrid effect in the copper matrix composites can be explained by the fact that a better strengthening effect was achieved by adding less hybrid reinforcement, which helped maintain the electrical conductivity at a relatively high level. (C) 2019 Elsevier B.V. All rights reserved.