Thermal Cycle Simulation And Structure Properties Of Magnesium Alloy By Variable Polarity Plasma Arc Welding

As a high-performance structural materials, magnesium alloy has low density, high specific strength, good damping, easy machining and good recyclability, etc, which is known as "the 21st century Green structural materials ", Magnesium alloy has been widely used in automobile industry, motorcycles industry and other fields need saving energy. Hence, more and more magnesium alloy welding applications are researched and promoted, efficient welding of magnesium alloys has become the actual industry demand.As a high-energy welding methods variable polarity plasma arc welding has high energy density, great welding speed, narrow weld heat affected zone advantages etc, which attract the researchers attention both at home and abroad. Simulation of the welding temperature field about variable polarity plasma arc in finite element method, would contribute to deeper understanding of the physical mechanism of the welding process, and also to achieve the guidance of welding process, welding quality control purposes.In this paper, 8mm thick wrought magnesium alloy AZ31B object was used, magnesium alloy AZ31B variable polarity plasma arc welding process was on the basis, combining the characteristics of AZ31B magnesium alloy using the ANSYS finite element analysis software, Double ellipsoid heat source model finite element analyzed the model, and using the temperature logger and thermocouple measurement of the actual welding process with the temperature cycle curve, the measured results with finite element analysis model to optimize the various parameters to adjust, so that finite element analysis model results would closer to the actual situation. Ensure the finite element model of accuracy, using the finite element model, respectively, for different welding current and welding speed of welding temperature field in numerical simulation. The results showed that: in the selected process parameters, the use of double ellipsoid heat source model of 8mm thick wrought magnesium alloy AZ31B variable polarity plasma welding temperature field of the finite element simulation is feasible.Welding thermal cycle process is the key factors to welding joints, welding thermal simulation technology imitation heat affected zone HAZ thermal cycle process could change the structure of magnesium alloys. In this paper, finite element analysis model of the thermal simulation results developed programs, Gleeble thermal simulation results showed that: heat cycle curve around the peak temperature exceeds 450℃, the grains tend to grow significantly, and hardness, tensile strength had decreased trend. Thermal cycle curve around the peak temperature of 270℃, the deformed occurred recrystallization, grain refinement occurs, and the grains had higher hardness and tensile strength.