Low Porosity in Cast Magnesium Welds by Advanced Laser Twin-Spot Welding
作者机构：Swerea KIMABKistaSweden University WestTrollhattanSweden TWI Ltd.CambridgeUK
出 版 物：《Materials Sciences and Applications》 (材料科学与应用期刊（英文）)
年 卷 期：2019年第10卷第1期
页 面：53-64页
学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学]
主 题：Laser Welding Cast Magnesium Twin-Spot Metallurgy Porosity Automotive AM50 Alloy
摘 要：Porosity is reported to be a major issue when welding cast magnesium. Therefore, it is important to understand the pore formation mechanisms and find procedures that could be used to reduce porosity. This study investigated the possibility of using twin-spot optics for reducing the porosity in laser welded cast magnesium. Two twin-spot welding setups were compared using either a beam splitter or twin-spot welding with primary and secondary (placed in front of the primary optic) optics. The results showed that welding with a dual optic setup with a defocused secondary beam reduced the volumetric porosity in the weld to 5%. The highest levels of volumetric porosity were 30%, and were a result of using the dual optic setup, but with a defocused primary beam. No clear relation between the level of porosity and power or welding speed was found. It was found that the amount of porosity depended on the balance of the energy input (controlled by defocusing) between the two beams. Porosity formation can be reduced if the energy from the first beam results in the nucleation and initial growth of pores. Reheating by the second beam then allows the pores to grow and escape from the molten material without melting additional base material. Furthermore, twin-spot welding is shown to be a promising combination of a production friendly solution and high quality welding.
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