Study On The Modification Of Iron-rich Phase In Al-5.2Zn-1.7Mg-0.5Cu Alloy

The demand for aluminum alloys in all professions and trades is increasing,but the use of electrolysis to produce aluminum alloys consumes a lot of resources and its emissions will cause serious pollution to the environment.Recycling scrap aluminum can avoid these situations.Iron(Fe)is the most harmful impurity element to aluminum alloy,and its content is very high in scrap aluminum.Therefore,if the scrap aluminum is to be recycled and put into use,it is necessary to remove the iron element.There are many ways to effectively improve the iron-rich phase in aluminum alloys,mainly the method of directly removing the iron phase and the method of modifying the iron-rich phase.This paper took Al-5.2Zn-1.7Mg-0.5Cu alloy as the research object,studied the influence of Fe content on the microstructure and mechanical properties of the alloy in the as-cast and extruded state,and observed the morphology of the iron-rich phase,Then,Al-5.2Zn-1.7Mg-0.5Cu alloy with a Fe content of 0.3%was selected,and the neutralizing element Mn was added to the iron-rich phase for modification.Concluded as follow:(1)When the Fe element content is 0.1%,Fe element exists in the form of lumpy Al₆(CuFe)phase.A little Fe can enhance the fluidity of the liquid alloy and improve the mechanical properties of the alloy.At this time,the tensile strength of the alloy is 326MPa,the elongation is 7.1%,and the alloy undergoes ductile fracture.When Fe element content is too high,it mainly exists in the form of acicular Al₃Fe phase,which will split the matrix.The mechanical properties of the alloy continue to decrease with the gradual increase of Fe content.When it increases to 0.5%,the tensile strength of the alloy is 253MPa,the elongation is 2.9%,and the alloy undergoes brittle fracture.(2)Extrusion makes the grain size of the alloy smaller and the structure more compact.The second phase is broken,especially the acicular Al₃Fe phase is broken,which weakens the splitting of the aluminum matrix and improves the structure and microstructure of the alloy.When the Fe content is 0.1%,the mechanical properties after extrusion are the best.At this time,the tensile strength reaches 402MPa and the elongation reaches 24.5%.Although the Al₃Fe phase is broken,it is still a brittle phase.With the increase of Fe content,the brittle phase also increases,which harms the mechanical properties of the alloy.The mechanical properties of the alloy are the worst when the Fe content is 0.5%.At this time,the tensile strength is 320MPa and the elongation is 12.1%.(3)When the Fe content is 0.3%,Mn can inhibit the acicular growth behavior of Al₃Fe,making it transform into fishbone shape and Chinese character shape,With the increase of Mn content,The conversion rate also increased gradually.When the Mn content is 0.3%,most of the acicular Al₃Fe phase evolves into a fishbone shape,the tensile strength of the alloy is increased to 312MPa,and the elongation is increased to 6.5%.The Mn element cannot completely neutralize the acicular Al₃Fe phase.If Mn continues to be added,too much impurity elements will be introduced to cause the iron phase to segregate,and the mechanical properties of the alloy will slightly decline.When Mn/Fe is 1.0,the iron-rich phase gets the best modification effect.The addition of Mn can not make the mechanical properties of the alloy reach the mechanical properties of the alloy when the Fe content is0.1%.It can be seen that too much Fe will cause great damage to the alloy properties.