Design And Characterization Of High Strength And Corrosion Resistant Casting Aluminum Alloys

A380 alloy is widely used in automotive,aerospace and industry,such as motorcycle gearbox,chassis and other electrical equipment.However,the A380 alloy has severe corrosion resistance in wet atmosphere or liquid due to a higher Cu content（3.0⁴.0 wt.%）with a higher electrode potential with respect to Al matrix,where electrical chemical micro batteries are easily formed.These corrosion problems will lead to the failure of component and resulted in the accident.Therefore,the objective of this research is to develop a new type of permanent mold casting and die-casting aluminum alloy with higher strength and corrosion resistance superior than A380 alloy.Setting A380 alloy as baseline alloy,the early corrosion behavior of A380 alloy was investigated by SEM and EDS mapping,and it was found that severe pitting mainly occured around the Al₂Cu and Al-Fe-Mn intermetallic phases.The DoE orthogonal matrix for 7 elements factors and3 levels including Si,Mn,Ni,Zn,Zr,Ti and V was presented.Design of experiment(L₂₇（3⁷）)from permanent mold casting was analyzed for higher mechanical and corrosion resistance properties,and the element influence of order on comprehensive properties was Zn,Ni,Mn,Si,V,Ti and Zr.The optimized compositon is 12-14 wt.%Si,0.7-0.9 wt.%Mn,0.5-0.7 wt.%Zn,0.2-0.3 wt.%Zr,0.2-0.3 wt.%Ti,0.2-0.3 wt.%V,0.3-0.5 wt.%Mg,0-0.6wt.%Fe,0.02-0.06 wt.%Sr,Al bal.Microstructure,mechanical and corrosion resistance properties of new alloy and baseline alloys were characterized.The results showed that the optimal alloy exhibited much better mechanical and corrosion resistance properties than that of A380.The optimal alloy also exhibited similar or better corrosion resistance than that of A360 alloy and fulfilled the goal in corrosion resistance of this project.In addition,all HPDC alloys exhibited a much finer microstructure along with improved mechanical properties and lower corrosion rate in comparison with A360 and A380 alloys.The study is beneficial for further alloy development.In addition,the experimental results provided a method to modify hypereutectic Al-Si alloy without copper content by minor additions of Ti,Zr and V contents to form blocky Zr-Ti-V-rich phase,correspondingly,the comprehensive mechanical properties were improved significantly.