Intentional Oxidation and Laser Remelting of Highly Reflective Pure Cu for Its High-Quality Additive Manufacturing

Laser processing of pure Cu is often challenging because of Cu's very low absorptivity to most laser beams, and this difficulty is applicable to the recently developed laser powder bed fusion (LPBF) additive manufacturing (AM). How to realize high-quality LPBF forming is urgently pursued to maximize its advanced manufacturing potential in directly making various Cu parts. Herein, two approaches have been applied, individually or simultaneously, to address the poor printability problem of the pure Cu: one is to conduct intentional oxidation treatment to the pure Cu powder to vary its surface structure and then enhance its laser absorptivity; and the other is to adopt laser remelting to counter its high thermal conductivity and provide extra liquid phase for better densification. Various research means were used to investigate mechanical performances, microstructural details, and electrical performance of the as-printed Cu. Results show that a maximum relative density of approximate to 99.0% can be realized by using the two approaches simultaneously, while oxidation temperature and remelting times are the two important factors to be considered. The methodology developed in this study is expected to be applicable to other highly reflective materials as well.