Nd:YAG 레이저 용접한 AZ31B-H24 마그네슘 합금의 용접성

Abstract

Because of its low density, high specific strength and superior properties for absorbing vibration and insulation electromagnetic interference, magnesium alloys have been used for structural components for automobile. However, those applications also were limited by its high oxidization tendency, low vapor pressure and poor ductility at the room temperature and poor weldability. Conventional fusion welding processes of magnesium alloys have several problems such as porosities, metal vapor, oxidation, distortion and etc. due to the high level of chemical activity and thermal conduction. On the other hand, laser welding is so much attractive process for magnesium alloys. Especially Nd:YAG laser welding is suitable for magnesium alloy due to short wavelength and low heat input, so that could rarely affect the metal plasma with Ar shielding gas. In this study, Nd:YAG laser welding of AZ31B-H24 magnesium alloy sheet was carried out with changing laser welding parameters. The effects of AZ61 filler wire addition were also investigated. Microstructure and mechanical properties of welded joint were examined by optical microscopy, scanning electronic microscopy(SEM), energy dispersive spectroscopy(EDS), electron transmission microscopy(TEM). Micro-vickers hardness and tensile test was also performed at the room and elevated temperature in order to investigate mechanical properties and the effects of filler wire addition on laser welded AZ31B-H24 magnesium alloy.