Research On Low-Power Laser-Tungsten Inert Gas (TIG) Hybrid Welding Technology Of Mg Alloy

For the characteristics of low density, high specific strength, good electromagnetic shielding, anti-radiation and recycleable, Mg alloys are praised of the green engineering material in 21st century, which have recently attracted great attention in academic research and industry application. Applications in aerospace vehicle, automobile, consumer electronic productions have been widely and rapidly extended. As a country with abundant Mg resource, the industrialization of Mg has been become the one of tactic aims of science and technology in our country. However, the single welding technique of Mg and its alloy can't meet the demands of manufacturing at present and it has been the main problem which limits the application of magnesium alloy structural components. Hereby, the research on Mg welding technology is becoming a focal topic all over the world in order to acquire the advanced joining technique with advantages of high quality, high efficiency and energy saving. So the research on hybrid welding technology comes into being.1. Low-power laser-TIG hybrid welding process combining with 500W YAG pulsed laser and a tungsten inert gas welding arc is put forward for Mg welding alloy firstly in this dissertation. Taking AZ31B, AZ61 and AZ91D commercial alloys as subjects investigated, the low-power laser-TIG hybrid welding behaviors of the AZ-based Mg alloys in similar and dissimilar are investigated, in terms of welding parameters, fusion-zone characteristics, mechanical properties, welding temperature fields and the behavior of arc plasma and laser-induced plume. The results of experiments indicate clearly that AZ31B AZ61 and AZ91D magnesium alloys can be welded easily by low-power laser-TIG hybrid welding process. The top surface of weld is smooth and continuous without defects such as spattering, crack and undercutting in high speed welding. Comparing the penetrations of laser TIG and hybrid welding, it is found that the penetration of hybrid welding is 2 times of TIG welding, and 4 times of laser welding. The speed of hybrid welding can achieve 3-5 times of TIG alone. The high speed image system of arc behaviors in hybrid welding of magnesium is set up, by which the photographs of arc behavior that laser and arc act on each other are obtained. It is found that there are three ways that laser and arc act on each other, according to which the model of that is found. Based on the experiment results and hybrid mechanism that laser and arc act on each other, three kinds of mechanisms that the penetration of laser-TIG hybrid...