Pure copper rods were additively fabricated by using a multibeam type laser metal deposition (LMD) device equipped with two blue diode lasers, and the influence of them on the rods was investigated. It is unknown how the rod changes with respect to the process parameters such as the laser power and the powder feeding rate. In this study, the laser power and the powder feeding rate were changed to form a pure copper rod in the LMD method, and the influence of them on the cross-sectional area of the rod was investigated. Moreover, the electrical resistance value of the rod was measured, and the influence of the laser power on the electrical resistivity was investigated. In addition, the elemental analysis of the cross section was performed by an electron probe microanalyzer, and the influence of the laser power was investigated. As a result, the cross-sectional area of the rod is slightly dependent on the powder feeding rate, and even if the powder feeding rate is increased, the cross-sectional area is slightly increased, but when the laser power is increased, the cross-sectional area is significantly increased. Moreover, when the laser power was increased, the electrical resistivity increased. The elemental analysis revealed that the surface of the rod might be oxidized, which suggested that it affected the electrical resistivity.

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Establishing processing routes for obtaining metal-matrix composites (MMCs) with uniformly-dispersed reinforcements is one of the main subjects in additively manufactured composite materials to achieve designed microstructures and mechanical properties. Here we report on the microstructural features of compositionally graded WC/Co-alloy composites additively manufactured by multi-beam laser directed energy deposition (multi-beam LDED). For tailoring microstructures of compositionally graded WC/ Co-alloy composites with uniformly-dispersed reinforcements, the combinational method: the laserbeam defocus function in the multi-beam LDED system and granulated powder was attempted. By laser defocusing in the multi-beam LDED system, composites with uniformly-dispersed WC particles in Co alloy matrix was successfully obtained due to melting of Co bond in WC-12 wt.%Co granulated particles. It was found that the laser defocusing of multi-beam lasers affects temperature increase of flying powder during the laser focusing area, resulting in change of processing mode from melt-pool mode to thermal spray mode. The preferable property gradients in the WC/Co-alloy composites could be obtained by controlling the feeding rate of the powders and laser-beam defocus. These experimental results demonstrated the effectiveness of the laser-beam-defocus function in the multi-beam LDED system as a key factor for tailoring microstructures of additively-manufactured functionally graded MMCs with uniformly-dispersed reinforcements.