The Microstructure And Properties Of Al-Mg Alloy By CMT-WAAM With Modification Treatment

Al-Mg alloy has properties such as lightweight,high strength,and excellent corrosion resistance,and is widely used in fields such as aerospace,shipbuilding,and automotive.However,due to the accumulated heat input and complex thermal cycling process during additive forming,there are defects such as pores,uneven microstructure,and coarse grains in the microstructure of Al-Mg alloy after additive forming.By adding heterogeneous particles between the deposition layers of CMT-WAAM Al-Mg alloy for modification,grain refinement,homogenization of structure,and suppression of dendrite segregation are achieved,thereby improving the microstructure and properties of CMT-WAAM Al-Mg alloy.The ER5356 Al-Mg alloy welding wire was used,La₂O₃and Ti C particles were added as modifiers respectively.The experimental parameters of modified CMT-WAAM Al-Mg alloy were optimized,and the macro forming quality of the precipitated parts was observed;Analyze the phase composition of the deposited parts by combining XRD and binary alloy phase diagram;Observe the microstructure of sedimentary components,analyze grain morphology,size,and orientation.Test the mechanical and tribological properties of the specimens,and analyze the laws of microstructure optimization and performance improvement of the deposited specimens.The optimal welding parameters for the modified CMT-WAAM Al-Mg alloy are welding current 95A,welding voltage 13.3V,welding speed 6mm/s,and the mass fraction of coated heterogeneous particles is 0.9%.Compared with uncoated deposited parts,the surface color of interlayer coated particles deposited parts is darker,the side wall transition is smooth,and the number of internal pores is reduced.Mg elements exhibit significant segregation and aggregation at interlayer junctions.When the welding current is 95A,La₂O₃particles are coated between layers to deposit CMT-WAAM Al-Mg alloy,and the grains are finer.La₂O₃particles mainly exist at the grain boundary and inside the grains.α（Al）andβ（Mg₅Al₈）has a more uniform microstructure,with an average grain size of 67.574μm to 49.696μm.The average microhardness of the deposit coated with La₂O₃particles increased by 3%;The tensile strength is increased by 12.79%,and the elongation after fracture is increased by1.5%.The fracture mechanism is microporous aggregation fracture.Due to the addition of particles to enhance the hardness of the deposited part and reduce plasticity,the depth and area of the tensile fracture toughness are shallower and smaller;Reduce the wear rate by 60%.