Effect Of Heat Treatment On Microstructure And Properties Of AlSi10Mg Alloy Prepared By Selective Laser Melting

In recent years,AlSi10Mg alloy has been widely used in aerospace,medical and other fields because of its low density and high specific strength,which meets the requirements of lightweight.The Selective Laser Melting(SLM)technology has attracted extensive attention due to its high cooling rate and fine grain size.The AlSi10Mg alloy was prepared by SLM method using AlSi10Mg metal powders,via controlling the scanning speed of experimental parameters.The relative density,porosity,microhardness,electrochemical impedance spectroscopy and potentiodynamic polarization curves of the SLM additive manufactured alloy were evaluated,the optimized process parameters of preparation AlSi10Mg alloy were determined in this thesis.Effect of heat treatment on microstructure and properties of AlSi10Mg alloy by selective laser melting has been investigated.The conclusions were drawn as:With increasing scanning speed,the relative density of AlSi10Mg alloy samples first increases and then decreases,and the densification of the surfaces was higher than that of its sides.When the laser power is 300 W and the scanning speed is 1.0m/s,its microhardness reaches up to 145.2HV.Electrochemical impedance value,self-corrosion potential and impedance phase angle are the highest in the studied parameters,and its corrosion resistance reaches the optimal.Through scanning electron microscopy and energy spectrum analysis,it can be seen that AlSi10Mg alloy is an oversaturated solid solution composed of α-al matrix and eutectic Si,and its morphology is fine cellular structure.Except for Si element,other elements are evenly distributed,and Si element is distributed on the surface of aluminum matrix in a grid.After two kinds of heat treatment of T74 and RRA,the microstructure observation and mechanical property tests show that the microhardness has fallen slightly after heat treatment,the maximum tensile strength decreases after two-stage aging,but elongation increases,and regards to three-stage aging,the maximum tensile strength and elongation close to that of the as received sample.Base on the investigation into the effect of heat treatment on the corrosion behavior of AlSi10Mg alloy,it can be found that the corrosion resistance of AlSi10Mg alloy with both heat treatment is reduced,which is totally different from the change of corrosion resistance after heat treatment of casting AlSi10Mg alloy.Both electrochemical corrosion and immersion corrosion results show that the as received samples have the best corrosion resistance.However,the corrosion performance of the materials before and after the heat treatment is better than that of the cast AlSi10Mg alloy with the same composition.