Research On The Preparation Process Of High Corrosion Resistance 7 Series Aluminum Alloy

7xxx aluminum alloys are widely applied in various fields with the characteristics of light weight and high strength.The 7xxx aluminum alloys are widely used,but their poor corrosion resistance limits their application on special occasions.Therefore,in the future development,exploring the preparation technology of 7xxx aluminum alloy with high strength and high corrosion resistance is very important for the actual production.In this paper,the homemade 7xxx aluminum alloy is the study object,the effects of Zn/Mg,deformation modes and retrogression and re-aging on the microstructure,mechanical property and corrosion resistance were investigated by using room temperature tensile test,exfoliation corrosion and electric conductivity,optical microscopy,X-ray diffraction and electronic microscopy analysis.The aim is to increase the corrosion resistance of the alloy under high strength.The conclusion is as follows:?1?With the increasing of Zn/Mg?2.1³.7?,the grains of the alloy are refined to a certain extent,while the precipitation of MgZn₂ phase is also increased;The mechanical properties of the alloy optimized,the tensile strength and elongation increased significantly;the conductivity and the exfoliation corrosion performance are slightly lower.However,when the content of elements in the alloy is too high,the non-equilibrium eutectic phase in the alloy will be large and aggregated,which will reduce the mechanical properties and corrosion resistance of the alloy.?2?The microstructure of hot forging consisted with fine recrystallized grains and non recrystallized regions,intermediate thermal-mechanical treatment?ITMT?after hot forging makes the alloy complete recrystallization,the forged grains is smaller than the rolled.The alloy has the highest tensile strength after hot forging,which is714MPa.In the subsequent deformation,ITMT after hot forging makes the alloy consume a lot of dislocations,the strength decreased,but the elongation increased;the cold rolling after hot rolling increased the dislocations of the alloy,the tensile strength increased.The forging process formed single chain precipitates at the grain boundary,and the rolling process formed a number of chain precipitates,in which the separation of grain boundary precipitates after ITMT and cold rolling is bigger than hot forging and hot rolling,which can effectively prevent the electrical chain reaction between the precipitates in the grain boundary,and the corrosion resistance of the alloy can be improved,but ITMT lost part strength,cold rolling not only improved strength,but also improved corrosion resistance of alloy.?3?Reasonable increased ITMT deformation quantity refined the grains of the alloy and increased dislocations density,which can improve alloy strength.However,when the deformation quantity is too high,the grains grow up while the dislocations density decreased,the strength reduced,and the corrosion resistance greatly improved.?4?With the increase of regression temperature and regression time,the precipitation of MgZn₂ phase increased,the strength of the alloy increased and then decreased,and the electrical conductivity increased continuously.The strength of the alloy reached the peak value,702MPa,at 190?×20min regression,when the regression temperature and the regression time continued to increase,the strength of the alloy decreased as the reinforced phase returned to the matrix.The electrical conductivity of the alloy began to rise obviously at 190?×30min regression,indicated that the corrosion resistance of the alloy was improved.