Mesoscopic Model Of Welded Joints Of Aluminum Alloy And Numerical Simulation Of Stress Change After Corroded

With good formability and weldability,A7N01 and 5083 aluminum alloys welded using ER5356 welding wire are becoming important materials in vehicle manufacturing.The corrosion pits on aluminum alloy welded structural parts under corrosive environment always become the source of fracture and failure,and seriously affect its service life and reliability.Since the macro-mechanical properties of materials are closely related to its mesoscopic behaviors,it is very essential to analyze its stress,deformation and their distributions characteristics at meso scale for optimizing welding parameters and structures design.Based on Voronoi algorithm,a three-dimensional mesoscopic structure model of aluminum alloy welded joint was built,which consisted of the polycrystalline regions of base metal equiaxial grains,fusion line columnar grains and weld seam equiaxial grains.Finite element calculations were carried on a selected model of size 0.8mm×0.6mm×0.18mm by using crystal plasticity finite element method.According to the initial grains orientation data determined by EBSD measurement,and crystal plasticity theory,a user-defined material subroutine was developed to study the mesoscopic deformation mechanism and stresses distribution of welded joints of 5083 and A7N01 aluminum alloys.In addition,salt spray corrosion tests were conducted on the welded joint of A7N01 aluminum alloy with ER5356 welding wire.The evolution of the morphology of corrosion pits with the time was studied.The mesoscopic tensile stress distribution of both as-welded and corroded joints were analyzed and compared by using elements birth and death technology.Results show that,under tension,the maximum stress appears at the binding region of columnar and equiaxial grains region in both the 5083 and A7N01 welded joints using ER5356 welding wire.It means the stress distribution fluctuated at?the binding region of columnar and equiaxial grains.After certain time of salt spray corrosion,the average depth and surface damage of corrosion developed in all regions of welded joints.Compared with the as-welded joints,the mesoscopic stress distribution of the corroded joints has higher nonuniformity,and the corrosion pits present round gradually.At the edge of the pits stress concentration is found.Maximum principal stress and the peak stress increased,which leads to the cracks initiation.Compared with tensile experiments,the simulation results are in accord with the experimental ones well.