Microstructure Evolution and Mechanical Properties of Needle-like ZrB(2) Reinforced Cu Composites Manufactured by Laser Direct Energy Deposition

Laser additive manufacturing is an advanced material preparation technology, which has been widely used to prepare various materials, such as polymers, metals, ceramics and composites. Zirconium diboride (ZrB(2)) reinforced copper composite material was fabricated using laser direct energy deposition technology. The microstructure and phase composition of the composite material were analyzed, and the influence of laser energy density on the microstructure and mechanical properties of composite materials was discussed. The results showed that the needle-like ZrB(2) ceramic reinforcement was successfully synthesized via an in-situ synthesis reaction. The composites were mainly composed of needle-like ZrB(2), Ni dendrites and a Cu matrix. The morphological changes of Ni dendrites could be observed at the interface inside the composite material: cellular crystals → large-sized columnar dendrites → small-sized dendrites (along the solidification direction). The continuous Ni dendritic network connected the ZrB(2) reinforcements together, which significantly improved the mechanical properties of the composite material. At a laser energy density of 0.20 kJ/mm(2), the average microhardness of the composite material reached 294 HV(0.2) and the highest tensile strength was 535 MPa. With the laser energy density increased to 0.27 kJ/mm(2), the hardness and tensile strength decreased and the elongation of the Cu composites increased due to an increase in the size of the ZrB(2) and a decrease in the continuity of the Ni dendritic.