||During the past years, the use of additive manufacturing (AM) technologies in a variety of fields has increased substantially. Because of the one-step manufacture and customization of designs, AM technologies have been more and more widely used in the application of the medical implants and aerospace components. |
Electron beam melting (EBM), which involves the layer-by-layer electron beam melting of powders, is one of the most promising AM technologies. However, the procedure of EBM process will make products get rougher surface due to melting pool which causes adjacent powder particles to be sintered to the surface without being melted. Under dynamic stress, notches caused by these bounded powders may cause stress concentration and may induce products fatigue. Hence, it is necessary to improve the surface quality by various post processes. On the other hand, internal or complicate structures are impossible to finish by conventional mechanical polishing methods. Therefore, electropolishing is a feasible method to improve the surface quality of Ti6Al4V EBM samples.
This study is devoted to evaluating whether the electropolishing method would be the effective method or not. Firstly, the best electrolyte and parameters for Ti6Al4V EBM samples are searched out by different experimental condition designs. Secondly, surface quality, such as surface morphology and notches on the surface, are observed with a view to discussing the influence of stress concentration. Thirdly, mechanical properties, such as Young’s modulus, elongation, and yield stress, are measured to discuss the influence of different degrees of roughness on the surface. Lastly not the least, the electropolished-porous samples are analyzed by micro-CT.
Experiment results show that the surface roughness of Ti6Al4V EBM solid samples can be improved from 23.4 μm to 5.3 μm by electropolishing with the electrolyte of perchloric acid, glacial acetic acid, and ethanol. For the Ti6Al4V EBM solid tensile specimens after optimum electropolishing, the tensile elongation can increase from 7.6% to 11.6%, with the surface roughness of the side surface of tensile specimen decreasing from 24.1 μm to 4.1 μm. However, for the porous Ti6Al4V EBM compression specimens, the results show that the polished porous specimens would result in worse mechanical property than the unpolished porous specimen, as a result of the over corrosion of external ligaments.