Pure Cu is a fundamental material for a large variety of industries including electrical power system and electronic industry. 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) as well. How to realize high-quality LPBF forming is urgently pursued in order to maximize its advanced manufacturing potential in directly making various Cu parts. In this study, 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 in order 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. Research means including electron back-scattered scanning diffraction, x-ray photoemission spectroscopy and eddy current electrical conductivity meter were used to investigate mechanical performances and provide microstructural details and electrical performance of the as-printed Cu that has been subjected to the intentional oxidation and/or laser remelting. Results show that a maximum relative density of ~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. Tensile strengths of 345-405 MPa, and electrical conductivity of 73-87%IACS have been achieved too. In the end, demonstrative parts of heat exchanger and flange are provided to highlight the capability of LBPF to form Cu parts.The methodology developed in this study is expected to be applicable to other highly reflective materials as well.
