Research On Structure And Property Of High Silicon Aluminum Alloy Laser Welding Joints And Temperature Field Simulation

High silicon aluminum material is widely used in electronic packaging in recent years. But this material with poor welding performance and has high tendency of forming cracks and pores. Pulsed laser welding with low line energy, fast welding speed and narrow heat affected zone, which can reduce thermal shock and be suitable for the welding of miniature parts and precision components.Lots groups of experiments on laser welding of high silicon aluminum alloy were carried out by using the solid pulsed laser welding machine in the article, and pulsed laser welding temperature field of high silicon aluminum alloy was researched by the numerical simulation method to grope for the suitable laser welding parameters. By comparing the weld size and the forming quality in three different focal length lens,120 mm focal length lens and +1mm defocusing amount were used in experiments. The optimal parameters of the laser welding were ascertained by using Simple Variable Method.The base metal structure of Al-27Si and Al-50Si alloy are mainly a-Al matrix and primary silicon. The weld structures are the primary silicon and Al-Si eutectic. The structures of heat affected zone are Al-Si eutectic and semi-molten silicon. The grains in weld area are more uniform and smaller than those of the base metal. The heat affected zone is the vulnerable part and the grains in heat affected zone show a great difference. The micro-hardness of the weld area is greater than that of the parent metal. Small micro-hardness fluctuation is observed in the base weld metal, however, widely fluctuation in the heat affect zone.During the thermal simulation, the smaller silicon granule grows up and Al-Si eutectic gradually appears with temperature rising, however, the amount of the porosity defect increases. To avoid weld defect and grains coarsening, the welding heat input was controlled and the high temperature residence time of weld structure was reduced.By comparing the hybrid heat source of gauss surface heat source and the three-dimensional cone heat source model, the temperature field distribution of laser welding process is obtained. With the increase of welding current, the size of molten pool increases obviously, the high-temperature area near the weld gradually rises, and the overall temperature of weld also gradually increase. With the increase of welding speed, the weld penetration and the high-temperature area near the weld gradually decreases, the overall temperature of weld also gradually reduced. During the welding process, the temperature of most area of base metal below 300℃ which shows a little impact on the internal components.