Effect Of Multi-microalloying And Ultrasonic Treatment On Microstructure And Corrosion Resistance Of ZL101 Alloy

In order to meet the lightweight requirements of shipbuilding weapons and equipment.Aluminum alloy castings have been widely used in shipbuilding industry.At present,traditional Al-Si cast aluminum alloys such as ZL101 and ZL104 are widely used in the field of shipborne equipment.Due to the problems of low strength and poor corrosion resistance,it is difficult to serve for a long time in high humidity and high salt environment.In this study,the effects of compound addition of Y and Zr elements and ultrasonic treatment on the microstructure,mechanical properties and corrosion resistance of ZL101 alloy in as-cast and T6 heat treatment state were studied,and the mechanism of compound strengthening of trace elements and ultrasonic action was explored,which provided an experimental and theoretical basis for the application of high-strength corrosion resistant aluminum alloy.The details are as follows:Firstly,the effects of the addition of Y and Zr on the microstructure and properties of as-cast ZL101 alloy were investigated.The secondary dendritic arm spacing of α-Al decreases with the addition of Y element,and the eutectic Si changes from lamellar to fibrous.When 0.3wt.% Y element and 0.25 wt.% Zr element are added,the eutectic Si has the strongest modification effect and the best mechanical properties.The yield strength,tensile strength and elongation reach 127 MPa,211MPa and 6.26%,respectively,which are increased by 20.95%,19.69% and 42.59% compared with ZL101 alloy.The corrosion resistance of the alloy is improved mainly because the iron-rich phase π-Al8 FeMg3Si6changes into π-Al8 FeMg3Si6Yx Zry,which reduces the potential difference between the alloy and α-Al.The composition of Al+7Si+0.3Mg+0.3Y+0.25 Zr alloy with the best performance as cast was finally determined.The effect of T6 heat treatment on the microstructure and properties of the alloy containing Y,Zr and other elements was systematically studied.After the T6 heat treatment,the mechanical properties of the alloy are significantly improved.In the ZL101+0.3Y+0.25 Zr alloy,the number of Al3 Zr particles increases significantly,and the size decreases,and the distribution of Al3 Zr particles in the alloy is more dispersed.Therefore,the mechanical properties of the alloy are significantly improved.The yield strength,tensile strength and elongation of the alloy reach 182 MPa,305MPa and 7.41%,respectively.After T6 heat treatment,Mg2 Si enriched at grain boundary is dissolved into the matrix,making it dispersed in the matrix as anode,which enhances the protection of Al alloy matrix and significantly improves the corrosion resistance of the alloy.The microstructure and properties of ZL101 and ZL101+0.3Y+0.25 Zr alloys treated by ultrasonic were studied.After ultrasonic treatment,cavitation and acoustic flow effect promote the transformation of α-Al grains from dendritic to nearly equiaxed.When the ultrasonic power is 1400 W,the mechanical properties of both alloys are the best.After T6 treatment,the tensile strength,yield strength and elongation of ZL101 alloy reach153.2MPa,255.3MPa and 6.83%,respectively.The tensile strength,yield strength and elongation of ZL101+0.3Y+0.25 Zr alloy reach 194.2MPa,323.7MPa and 8.67%,respectively.Moreover,due to the transformation of grain morphology,the eutectic silicon at the grain boundary of equiaxed grains impedes the expansion of corrosion zone,which effectively improves the corrosion resistance of the alloy.