Research On Processing And Forming Mechanism Of ZK61Magnesium Alloy By Selective Laser Melting

As the lightest metals, magnesium alloys have broad application prospects in thefields of aerospace, electronics and military. In fact, applications of magnesium alloys fallbehind other metals by the constraints of physical chemistry and processing characteristics.Selective laser melting (SLM) technology is expected to solve the traditionalmanufacturing problems of magnesium alloys and expands their applications due to itstechnical advantages. However, few reports are found on researches of formingmagnesium alloys by SLM.In this paper, powders of ZK61magnesium alloy are used as the starting material forSLM processing. The effects of laser forming parameters on the densities of SLMedsamples, ablation behavior of elements and forming mechanism of microstructures havebeen studied in detail.Experimental results show that densities of SLMed samples increase with the laserenergy density. Especially, laser power plays the most key role to control densities ofSLMed samples compared with the overlap ratio and scanning velocity. For the scanningvelocity, it seems have no obvious effect on densities of SLMed samples. The densities ofSLMed ZK61samples are greater than96%when laser power is160-200W, scanningvelocity is10-30m/min and the overlap ratios are greater than0.4.During SLM processing, the main ablated element is magnesium. The ablation ofmagnesium can be restrained by increasing the laser energy density to form Mg-Zn solidsolutions quickly. The ablation of element is serious at a relatively lower scanningvelocities and higher overlap rates though the density is very high. Thus, higher densityand lower ablation of element of the SLMed samples can be realized by increasing thescanning velocity at a relative high laser energy density.The grain size of SLMed ZK61is tiny and about one twentieth of that of traditionalfoundry material. A new magnesium-zinc phase of Mg0.97Zn0.03occurs when the laserpower is higher than120W, which is benefit to enhance mechanical properties of theSLMed ZK61samples. Small grains induced by very high heating and cooling rates andthe occurence of Mg0.97Zn0.03are helpful to improve the microhardness of SLMed ZK61 samples. The microhardness of SLMed samples reaches Hv163, is about Hv60to100higher than that of the traditional foundry magnesium alloy.