Study On Friction Stir Welding Technology And Microstructure Properties Of Vehicle Charger Electronic Control System Components

In the manufacturing of new energy vehicles,the electronic control system of the onboard charger is packaged by the shell made of Al Si10 Mg aluminum alloy and the cover plate made of Al Si10 Mg and 5052 aluminum alloy respectively.In this paper,friction stir welding technology is used to weld the actual workpiece packaging parts.The purpose is to analyze and test the microstructure and mechanical properties of Al Si10 Mg aluminum alloy welds and Al Si10 Mg and 5052 dissimilar aluminum alloy welds under different welding parameters,optimize welding parameters to reduce specimen defects and improve workpiece performance.The microstructure evolution of different regions in the joint of Al Si10 Mg aluminum alloy and 5052 aluminum alloy was investigated.Under the action of the stirring tool,the phase distribution of Al Si10 Mg aluminum alloy changes obviously.The eutectic silicon and needle-like iron-rich phase are distributed in the original base metal and the streamlined distribution in the thermo-mechanically affected zone.The fine granular distribution in the stirring zone.Because the phase content of 5052 aluminum alloy is small and granular,there is no obvious change in phase distribution after welding.The effects of different welding parameters(stirring tool rotation speed,axial pressure,welding speed)on the forming and mechanical properties of Al Si10 Mg aluminum alloy friction stir welded joints were investigated.The experimental results show that the influence of welding parameters on the joint is mainly attributed to the change of heat input.When the heat input is low,there are defects inside the weld.When the heat input increases,the defects disappear,but the surface flash increases and the cross section of the weld changes from a shape close to the stirring pin to a shape close to the cone.The hardness distribution of the weld cross section is approximately ’ W ’-shaped,and the stirring zone increases with heat input.The microstructure of Al Si10 Mg and 5052 aluminum alloy joints were analyzed,and the grain size and texture changes of the two materials during welding were investigated.The test results show that due to the different effects of the stirring tool in each region,the content of high-angle grain boundaries and recrystallized structures from the base metal to the weld stirring area decreases first and then increases,and the grain size increases first and then decreases.The fine second phase in the weld stirring zone can pin the recrystallized grains and inhibit grain growth.The texture of the base metal is related to its processing state.The texture of the heat affected zone is basically the same as that of the base metal.The stirring zone and the thermo-mechanically affected zone are strongly affected by the mechanical action of the stirring tool.The original textures of the base metal disappears and the textures changes significantly.The effects of heat input changes on the weld formation and mechanical properties of Al Si10 Mg and 5052 dissimilar aluminum alloys were investigated when the materials were in different relative positions(advancing side and retreating side).The results show that the influence of heat input on the surface forming and tensile strength of dissimilar aluminum alloy joints is the same as that of the same aluminum alloy.When the 5052 aluminum alloy at the advancing side,the weld surface forming,the tensile strength of the joint and the mixed state of the two metals in the weld stirring zone are better than the Al Si10 Mg aluminum alloy on the advancing side under the same parameters.Among them,5052 aluminum alloy at the advancing side.When the welding parameters are 4200 N,1400 rad / min,and 360 mm / min,the tensile strength of the joint reaches the highest value of 208 MPa,which reaches 94.5 % and 74.3 % of the strength of 5052 and Al Si10 Mg aluminum alloy respectively.The hardness value of the cross section of the dissimilar aluminum alloy joint is approximately stepped.The influence of heat input change on the hardness distribution is mainly related to the mixing state of the two alloys.Using the optimized parameters of the welded specimens,non-destructive testing,air tightness testing,and flatness error measurement,the results meet the use requirements.