Abstract
Magnesium alloy is the lightest structural material among commercial alloys and is widely used for electronic product cases such as laptops, PCs, and mobile phones due to its excellent specific strength and electromagnetic wave shielding properties compared to other lightweight materials. In addition, Mg-Li-based alloys with the addition of Li, an ultra-light metal element, are attracting much attention as materials for aerospace such as rockets and missiles because they can dramatically lower the density of conventional magnesium to increase specific strength. However, due to poor strength and moldability at room temperature, application to actual parts is limited. Since the crystal structure of magnesium is a dense hexagonal (hcp) structure, the room temperature slip system required for plastic deformation is limited, resulting in low formability. In this study, magnesium alloys with different HCP and BCC phase fractions were prepared by adding 6, 8, and 10 wt% of Li element to improve the formability of magnesium, and the microstructure, mechanical properties, and welding characteristics according to the phase fraction change. A study was conducted on Each magnesium alloy specimen was gravity cast in an SF6 + CO2 gas atmosphere using an electric furnace, and after homogenization at 350 ° C for 4 hours, direct extrusion was performed at 200 ° C to produce an extruded material having a thickness of 4 mm and a width of 50 mm. An optical microscope, SEM, etc. weMagnesium alloy is the lightest structural material among commercial alloys and is widely used for electronic product cases such as laptops, PCs, and mobile phones due to its excellent specific strength and electromagnetic wave shielding properties compared to other lightweight materials. In addition, Mg-Li-based alloys with the addition of Li, an ultra-light metal element, are attracting much attention as materials for aerospace such as rockets and missiles because they can dramatically lower the density of conventional magnesium to increase specific strength. However, due to poor strength and formability at room temperature, application to actual parts is limited. Since the crystal structure of magnesium is a dense hexagonal (hcp) structure, the room temperature slip system required for plastic deformation is limited, resulting in low formability. In this study, magnesium alloys with different HCP and BCC phase fractions were prepared by adding 6, 8, and 10 wt% of Li element to improve the formability of magnesium, and the microstructure, mechanical properties, and welding characteristics according to the phase fraction change. A study was conducted on Each magnesium alloy specimen was gravity cast in an SF6 + CO2 gas atmosphere using an electric furnace, and after homogenization at 350 ° C for 4 hours, direct extrusion was performed at 200 ° C to produce an extruded material having a thickness of 4 mm and a width of 50 mm. An optical microscope, SEM, etc. were used for microstructure and phase analysis, X-ray diffraction analysis was used for phase analysis, and argon welding was used to bond the samples according to the change in Li addition amount. Tensile tests were conducted at room temperature to evaluate the mechanical properties of extruded materials and welded samples.re used for microstructure and phase analysis, X-ray diffraction analysis was used for phase analysis, and argon welding was used to bond the samples according to the change in Li addition amount. Tensile tests were conducted at room temperature to evaluate the mechanical properties of extruded materials and welded samples.