Transient Melt Pool Dynamics Analysis of AZ31B Magnesium Alloy Based on ARMLPW Process

In order to replicate the ARMLPW’s process, a proposed model combines a heat source in the center with a heat source in the shape of a ring. To check the accuracy of the model, a heat-fluid coupling model was developed for the ARMLPW process using the magnesium alloy AZB31. After validating the heat source model with experimental data, a comparison was made of the transient shape of the molten pool during penetration welding, both with and without the ring-shaped heat source. The results confirm the accuracy of the heat source model, as they indicate that the volumetric heat source model for simulated ARMLPW welds closely matches the experimental welds. By employing the ring-shaped laser in the designated area, a significant molten pool and deep keyhole are rapidly formed, while having minimal impact on the unaffected area. The influence of the ring-shaped heat source results in noticeable variation in shape and size between the upper and lower sections of the molten pool and keyhole in the base material. These variations are responsible for the bulging observed in the middle of the weld seam, and the high-frequency fluctuations in the surface shape of the molten pool and the highest temperature of the keyhole are closely associated with the movement of the laser heat source. When considering fluid dynamics and heat transfer, there are two primary factors contributing to the formation of the “bulge” weld under the ARM laser beam. The first reason is the intense heat exchange that occurs between the middle and lower parts of the base material. This heat exchange leads to the transfer of upper heat to the middle part, resulting in an increase in the volume of the middle section of the molten pool. The second reason is the impact of the vertical component of the velocity perpendicular to the molten pool wall in the middle section.