Study On The Pure Mg Powder And Microstructure And Properties Of Forming Part By Selective Laser Melting

As the lightest metal materials, magnesium and its alloys have been widely used in automobile, aerospace, military, electronics industry and so on at present.They also have been widely studied as a biomedical implant materials due to their good biocompatibility, mechanical compatibility and biodegradable properties.However,because of their high corrosion rate and the forming characteristics, restricted the application and development of magnesium and its alloys in biological implant material.Its actual application is far behind other metallic implant materials.Selective laser meltig(SLM) is regarded as a new additive manufacturing technology, which is rapidly developed and researched in recent years becauseof its own unique advantages. The forming parts are not subject to the restriction of structure and shape, can realize customization manufacturing of complicated parts. And laser rapid melting and solidification process can greatly refine the microstructure, improve all aspects of the performance.Therefore, SLM technology is expected to be a new path to fabricate custom implants of magnesium based materials.In this paper, pure magnesium powder was used as the raw material. The laser equipment of EOS M280 was used to study the effect of laser parameters, powder size and scanning time interval on the forming quality, respectively. By reasonable selection of powder and process optimization, the bulk net-shape pure magnesium was fabricated by SLM process.The abnormal phenomena and forming defects during SLM process have been analyzed in the experiment. The microstructure and properties of SLM specimen with the optimal process have been studied. Electro-chemical corrosion test on SLM magnesium made preliminary study about its corrosion behaviour in SBF solution.The main conclusions of this paper have been obtained:① The SLM process of Mg powder was studied, the effects of scan speed and laser power on the forming process and forming parts have been mainly analyzed. A set of optimized process parameters has been obtained, and the bulk net-shape Mg has been first successful fabricated.② The first time to studied the effect of the scanning time interval(STI) on the quality of SLM Mg. Results indicated that when the STI was 50 s, the optimal surface of the specimen. At the same time, the sample has a minimum surface roughness and the highest microhardness.③ Particle size significantly affects the properties of SLM magnesium. The results showed the specimen exhibited better topology, higher relative density and higher micro-hardness of-250 mesh powder which compared to-400 mesh powder④ The microstructure of SLM magnesium existed obvious directivity, and it was related to laser scanning strategy. Microhardness test found that the SLM Mg raised about 45% compared with the cast specimens.⑤ The electrochemical corrosion test results showed the corrosion potential of SLM magnesiun was higher than the as-cast sample, but corrosion current density of the as-cast sample was lower than SLM samples.