Effects of Scanning Strategy on the Densification and Microhardness of Selective Laser Melting Mg–Y–Sm–Zn–Zr Alloy

Abstract

Selective laser melting (SLM) technology is an essential technology in laser powder bed fusion (LPBF) additive manufacturing and has attracted attention because it can produce highperformance near-net-shape parts. [1] SLM technology uses computer-aided design (CAD) to model parts in three dimensions. The model was then sliced into two dimensions using the software. [2] The metal powder is laid layer-wise according to the set thickness. The high-energy laser beam melts the powder layer by layer according to a predetermined scanning path, and finally obtains complex parts. [3] Due to the advantages of high precision and low material loss, SLM technology is widely used in aerospace, biomedicine, and other fields, as well as the production of aluminum, titanium alloys, steel, and other materials. [4][5][6] Magnesium alloys are considered the lightest structural metal materials. [7] However, magnesium alloys prepared by casting will produce defects such as shrinkage cavities, pores, inclusions, and composition segregation. [8] This will limit its development. Therefore, the researchers used SLM technology to design magnesium alloy parts. This technology makes up for the shortcomings of traditional processing methods and improves the comprehensive properties of magnesium alloys. [9] The SLM processing has the characteristics of point-by-point scanning, line-by-line connection, and layer-by-layer deposition. This results in a complex thermal history and thermal cycling of the part. The energy input of the local high-energy laser beam can lead to complex molten pool flow behavior. [10] Therefore, the formed parts will generate pore defects affected by the above-mentioned complex factors. The scanning strategy directly changes the scanning path of the laser, which will affect the transmission of laser energy in the metal powder, resulting in different melting and solidification behaviors of the material, and thus has a significant impact on the type and distribution of pore defects formed in parts. [11] Guo et al. [12] compared the AlSi10Mg bulk prepared by the island and conventional scanning strategies. Concluded that the relative density of the island scanning strategy is higher than that of the conventional scanning strategy. Lu et al. [13] used the island scanning strategy to fabricate Inconel-718 blocks. The study showed that the scanning strategy with the smallest island size reduces the relative density due to the accumulation of powder on the island boundary, resulting in a higher porosity than other island sizes. Kudzal et al. [14] obtained 17-4 stainless steel tensile samples using powder bed fusion technology and explored the relationship with porosity by using different scanning strategies. The study showed that the scanning strategy would affect the type of pore defects. By comparing the island scanning strategy, zigzag scanning strategy, and remelting scanning strategy, Gu et al. [15] found that defects will appear on the surface of samples prepared by island scanning and zigzag scanning strategies. Still, ...

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