9. Nano/Micron W–Cu Composites by Direct Metal Laser Sintering (DMLS) Additive Manufacturing (AM): Unique Laser-Induced Metallurgical Behavior of Insoluble System

The densification behavior and attendant microstructural characteristics of the direct metal laser sintering (DMLS)-processed nano/micron W–Cu composites under different processing conditions were investigated. The methods for improving the controllability of laser processing were elucidated. A “linear energy density (LED)” parameter, which was defined by the ratio of laser power to scan speed, was used to tailor the powder melting mechanisms. It showed that using a suitable LED between ~ 13 and ~ 19 kJ/m combined with a scan speed less than 0.06 m/s led to a continuous melting of the Cu component, yielding a sound densification rate without any balling phenomenon. A “volumetric energy density (VED)” parameter was defined to facilitate the integrated process control by considering the combined effect of various processing parameters. It was found that setting the VED within ~ 0.6 and ~ 0.8 kJ/mm³ favored a better yield of high-density DMLS parts. The influence of Cu-liquid content on densification and microstructures of DMLS-processed nano/micron W–Cu was also studied. It showed that at a suitable Cu elemental content of 60 wt.%, a series of regularly shaped W-rim/Cu-core structures were formed after DMLS processing. The metallurgical mechanisms for the formation of such a novel structure were proposed.