Microstructure And Properties Research Of Wire Arc Additive Manufacturing Al12Si Alloy

Aluminum-silicon alloy is widely used because of its good corrosion resistance,wear resistance and high specific strength.Arc additive manufacturing is a hot research topic in recent years.In this paper,ER4047 aluminum alloy is used as the filler wire,and the processability of the four arc mode additive manufacturing Al12Si alloys of CMT(Cold Metal Transfer),the formation of the microstructure of the addictive manufacturing sample,and the effect of annealing treatment on the microstructure and mechanical properties of the addictive manufacturing sample are mainly studied.The main research results are as follows:After studying the CMT arc additive manufacturing process,it is found that the morphology of the deposited layer is better when the welding speed is matched with the wire feeding speed during the additive process.Among the four arc modes,the CMT-P arc mode additive sample has better surface morphology and better comprehensive mechanical properties.The tensile strength can reach 225 MPa,and the elongation after fracture can reach 18%.The porosity of the addictive manufacturing sample is 0.19%,the structure is dense,the pores are randomly distributed in the addictive manufacturing sample,and the larger the pore size,the worse the sphericity.The microstructure of CMT arc additive manufacturing Al12Si alloy is a typical hypoeutectic structure with fine structure.The average thickness of lamellar eutectic Si is 310nm.The morphology of the eutectic Si structure in the intra-layer structure of the addictive manufacturing sample is mostly lamellar,and the morphology of the eutectic Si in the interlayer structure shows a mass.Al atoms adhere to the unmelted?-Al dendrites to continue to grow,so that the?-Al dendrites can continue to grow through the multilayer remelting zone.Different positions from the substrate have different heat dissipation modes,resulting in different microstructure morphologies at different positions:most of the?-Al dendrites in the sample near the substrate grow staggered and have short lengths,and the?-Al dendrites in the middle of the sample Most of the crystals are parallel to each other and have a long length.The?-Al dendrites on the top of the sample far away from the substrate grow staggered and have a short length.During the additive process,the average temperature of the molten pool can reach1121?,and the cooling rate is 3.0×10²?1.6×10⁴ K/s.The high overheating and fast cooling rate enable CMT arc additive manufacturing Al12Si alloy to obtain nano-scale ultra-fine structure.By studying the effect of annealing temperature and time on the structure and mechanical properties of CMT arc additive manufacturing Al12Si alloy,it is found that annealing treatment can spheroidize the lamellar eutectic Si in the structure,reduce the stress concentration at the tip of the eutectic Si,and improve the material The plasticity and growth law of eutectic Si conform to the Oswald aging process equation?²?₀² 2.26×10^-15exp(-24944.86/8.314T)t.When the annealing temperature reaches 500?and above,the spheroidizing effect is obvious.With the increase of annealing temperature or annealing time,the lamellar eutectic Si gradually spheroidizes and the thickness increases,the tensile strength of the sample decreases,but the elongation after fracture increases.After annealing at 500?,the tensile strength decreased from 225 MPa to 177 MPa,and the elongation after fracture increased from 18%to 30%.After annealing at 550?,the tensile strength of the sample decreased from 225 MPa to 192 MPa,and the elongation after fracture increased from 18%to 27%.