Metallurgical mechanisms in direct laser sintering of Cu–CuSn–CuP mixed powder

This work presents a detailed investigation into the metallurgical mechanisms in direct laser sintering of a multi-component Cu-based metal powder consisting of a mixture of Cu, Cu–10Sn, and Cu–8.4P. The phases, compositions, and microstructures of the laser sintered sample were characterized by XRD, EDX, and SEM. It is found that laser sintering of this powder system is based on the mechanism of liquid phase sintering with the complete melting of the binder Cu–10Sn and the non-melting of the structural metal Cu. The phosphorus element can act as a deoxidizer to prevent both the sintering mixture and the sintered layer from oxidation by formation of P2O5 and CuPO3, thereby improving the liquid–solid wettability and the resultant interlayer bonding coherence. The phosphorus element shows a high concentration along grain boundaries in the sintered structure, due to a low mutual solubility of P in Cu and an extremely short thermal cycle of laser sintering.