The Effect Of Cr And Cu Addition On The Corrosion Resistance Of Al-Mg-Si Cast Alloy

Al-7%Si-0.3%Mg cast aluminum alloy has good mechanical properties and is easy to be cast.Adding other alloying elements can improve its strength by controlling the type and number of precipitated phases through heat treatment.Thus,it can meet the standard of traditional steel materials in automobile industrial applications effectively and reduces the weight of vehicles and plays a role in energy conservation and emission reduction.However,at the same time,aluminum alloy parts of automobiles are usually exposed in relatively harsh physical and chemical environments,and the corrosion resistance of aluminum alloys is relatively high.Therefore,it is necessary to study the influence of added elements on the corrosion resistance of aluminum alloys.In this paper,the effect of Cr and Cu are investigated by using three kinds of cast aluminum alloys: Al-7%Si-0.3%Mg,Al-7%Si-0.3%Mg-0.3%Cr,Al-7%Si-0.3%Mg-1.5%Cu to study the effect of the addition of elements on the corrosion resistance of aluminum alloys.The effects of different additive elements on the corrosion potential,corrosion rate and surface microstructure of the aluminum alloy in different heat treatment conditions are studied by using the three-electrode system electrochemical workstation,SEM,TEM and EDS spectra.The role of the added element also depends on the state of the artificial aging process of the aluminum alloy.Samples in the aging peak with the highest mechanical strength are the most sensitive to corrosion.The addition of Cr increases the corrosion resistance of Al-7%Si-0.3%Mg,which can reduce the corrosion rate by 12.8% to 58.4% according to different artificial aging conditions,and the maximum reduction is for peak aging samples,while the pitting due to corrosion takes place in the surface more uniformly.On the basis of the addition of Cr,the addition of Cu can apparently reduce the corrosion resistance of aluminum alloy.For the alloys with different heat treatment conditions,the addition of Cu can increase the corrosion rate by 26.8% to 269.2%,which affects the peak aging and overaging samples most.The influence is less evident for underaged samples.At the same time,the addition of Cu aggravates the aggregation of pitting corrosion in the primary step of corrosion of aluminum alloy and the intergranular corrosion around and within the pitting hole,and promotes the formation of Si-rich particles on the surface of the alloy.