Oscillating laser-arc hybrid additive manufacturing of AZ31 magnesium alloy

Laser-arc hybrid additive manufacturing with beam oscillation (O-LHAM) was introduced to fabricate AZ31 magnesium alloy thin-wall components. The effect of the beam oscillating frequency on the morphological characteristics, internal porosity, microstructure, and mechanical properties was investigated. It was found that increasing oscillating frequency is effective to suppress the imperfections of lack of fusion, height differences, and wavy hump, as well as the number and size of internal porosity. The beam oscillation was beneficial to fragmentizing the average grain size and promoting the precipitation of Al8Mn5 and Mg17Al12 phases by generating stirring laminar flow in the molten pool, and it can disrupt the grain structure and provide more nucleation sites. Compared to the case without beam oscillation, the average grain size range decreased from 22-32 μm to 18-20 μm when the frequency increases to 300 Hz, while the precipitation percentage increased from 1.42-1.61% to 2.55-3.32%. For the components without porosity detected by the X-ray nondestructive test, the ultimate tensile strength and the elongation were 205 MPa and 20.7%, respectively, which are higher than those of AZ31 cast magnesium alloy. The tensile fracture has characterized the dimples with a small part of ductile tearing ridges, showing good ductility. The results indicated that O-LHAM would be effective to solve the tough problems in deposition quality and efficiency of additively manufactured Mg alloys.