Role of Oxides in the Tensile Properties of Pure Copper Processed by Laser Powder Bed Fusion

Oxide particles can affect the tensile properties of pure Cu processed by laser powder bed fusion (LPBF) through their interactions with dislocations. This study compared the microstructure and tensile behavior of samples produced from virgin and oxidized pure Cu powders under identical LPBF conditions. The two samples had comparable relative densities above 98.7% and similar grain sizes. Yield and ultimate tensile strengths were nevertheless higher in the oxidized sample, whereas uniform and total elongations were lower. Backscattered-electron imaging and image analysis indicated that oxide particles occupied a higher apparent area fraction in the examined fields of the oxidized sample; electron backscatter diffraction analysis also showed higher kernel average misorientation. Together, these observations suggest two possible roles for oxide particles: acting as dispersed obstacles to dislocation motion and promoting dislocation retention during LPBF, consistent with the higher kernel average misorientation. The strength increase may therefore reflect both particle strengthening and a greater contribution from dislocation strengthening.