Research On Microstructure And Corrosion Resistance Of AlSi10Mg Alloy Formed By Selective Laser Melting

AlSi10Mg alloy has the advantages of low density,high strength,good mechanical properties,and corrosion resistance,and is widely used in biomedical,transportation,aerospace,and other fields.Selective laser melting(SLM)forming technology can manufacture complex parts without molds,with high material utilization rates.SLM formed AlSi10Mg alloys have better mechanical and corrosion properties than casting,but high residual stress,anisotropy,and porosity are the disadvantages of this process.Although heat treatment can be used to improve,heat treatment can also significantly affect the corrosion properties of materials.At the same time,The corrosion behavior of AlSi10Mg alloy formed by SLM at different construction angles has not been studied.Therefore,in this paper,based on the application of AlSi10Mg alloy in the field of navigation,samples of AlSi10Mg alloy with different construction angles were prepared using SLM forming technology,and the effects of different construction angles and residual stresses on the microstructure and corrosion resistance were studied.At the same time,AlSi10Mg alloy blocks were prepared using SLM forming technology and subjected to heat treatment to explore the effect of heat treatment on the microstructure and corrosion resistance of AlSi10Mg alloy formed by SLM.(1)The effects of microstructure anisotropy and residual stress on corrosion resistance of AlSi10Mg formed by SLM at different construction angles were studied.The results show that there are different corrosion behaviors on the surface of SLM formed AlSi10Mg alloy samples with different construction angles.The corrosion current density and EIS results of the potentiodynamic polarization curve indicate that the corrosion resistance sequence is Braced 45°>Unbraced 45°>Vertical 90°>Horizontal 0°.The pitting potential results show that the order of pitting resistance is Braced 45°>Unbraced 45°≈Horizontal 0°>Vertical90°.Corrosion morphology observation indicates that corrosion preferentially occurs at the boundaries of pores and molten pools.Porosity,grain size,and distribution are important factors that affect the corrosion resistance of SLM formed AlSi10Mg alloys with different construction angles.Poor grain boundary orientation,grain plane orientation,and residual stress have limited effects on the corrosion resistance of the samples.(2)The effect of chloride ion concentration on the corrosion process of SLM formed AlSi10Mg alloy with different heat treatment regimes was studied.The results show that heat treatment at 300℃ and 400℃ can destroy the Si network of SLM formed AlSi10Mg alloy into dispersed Si particles,and the size of Si particles gradually increases with the increase of heat treatment temperature.Pitting caused by Si particles is the main reason for degradation of AlSi10Mg alloy formed by SLM after heat treatment.The size of Si particles and the concentration of Cl~-can affect the pitting corrosion degree of SLM formed AlSi10Mg alloy,resulting in different corrosion processes of SLM formed AlSi10Mg alloy in 0.1 mol/L and 1mol/L NaCl solutions after different heat treatments.At the same time,the combination of electrochemical noise(EN)measurement and comprehensive signal analysis is an effective method for studying the corrosion behavior of AlSi10Mg alloy fabricated with additives.(3)The effects of different aging times at low temperature on the microstructure and corrosion resistance of AlSi10Mg alloy formed by SLM were investigated.The results show that after low temperature aging treatment at 170℃,the AlSi10Mg alloy formed by SLM still maintains a molten pool and network structure,and the network structure contains a large number of nanoscale Si particles.With the aging time extended to 24 hours,the Si particles coarsened to about 100 nm,but the amount decreased.After low temperature aging at 170℃,the pitting potential of the alloy decreases and the corrosion current density increases,which means that the corrosion is intensified.As the aging time extends to 24 hours,the pitting potential continues to decrease and the corrosion degree deepens,possibly due to the precipitation of Si during the aging process.Due to the formation of Si particles,pitting sensitivity is increased.The observation of corrosion morphology shows that after aging,the number and size of corrosion pits on the surface of the sample increase,which means that the corrosion degree is deepened.