Study On The Microstructural,mechanical Properties And Corrosion Resistance Of 5083 Alloy By Zn Element

5083 aluminum alloy is one of Al-Mg series aluminum alloy with moderate strength,superior corrosion resistance,high ductility and moderate formability.It has been widely used in aerospace and transportation.The strength is the primary limitation on 5083 aluminum alloy,therefore the recent hot spot lies on improving the strength of this material.In this work,castability of 5083 aluminum alloy with different mass fraction of Zn element was investigated using water-cooling mold method by which the effect of rapid solidification on the segregation of solute elements was studied.Aluminum alloy with nanograin size was manufactured by severe plastic rolling.Water-cooling mold casting can solid the alloy rapidly and reduce the segregation degree of the solute elements.Afterwards,the alloy was homogenizing treated.The ideal homogenizing principle was 475 ? ×10h.Working hardening ability of 5083 aluminum alloy was raised after adding Zn,and the grain size can reach roughly 200nm.Herein,5083 aluminum alloy with different Zn content was investigated using ICP,SEM,OM,XRD,EDAX,electrochemical workstation and TEM.Microstructure and mechanical properties was characterized via tensile tests,hardness test and corrosion test.The main content is as follows.(1)Rapid solidified 5083 aluminum alloy with a high supercoiling degree was realized using a designed water-cooling copper mold.Equiaxed grains with size of about 50-60?m were obtained.Meanwhile,it was found that the intermetallic compounds on grain boundaries of cast alloy were remarkably reduced.(2)Solubility of the solute elements of the cast and homogenizing treated 5083+xwt.%alloy was estimated according to XRD analysis and Vegard's principle.The results showed that segregation degree of the solute elements Mg and Zn was reduced via rapid solidification by the water-cooling copper mold.As Zn content rises,Mg and Zn can easily separate the intermetallic compounds out,and solubility of Mg decreases.The addictive Zn element hinders Mg element in the cast alloy to dissolve in the matrix of the alloy.(3)Increasing the mass fraction of Zn element can raise the tensile strength of the cast alloy.Aluminum alloys with Zn of 0%,1.5%,3%and 5%had different tensile strength of 160MPa,171 MPa,245MPa and 365MPa while their ductility were less than 1%.Fracture analysis showed the fracture mechanism of the cast alloy is dominated by cleavage fracture.(4)The study showed that for the cast alloy homogenizing treated based on 475?×10h,the majority of Mg and Zn element were dissolved within the grains whose sizes do not increase and no over burning occurred.Hence,the ideal homogenizing principle was 475?×10h.Rapid solidification using the water-cooling copper mold reduced the duration of homogenizing treatment as well as the energy dissipated during homogenizing treatment.Component analysis on the residual second phase in the grain boundaries revealed that the intermetallic compounds were mainly composed of Fe and Si.(5)Mechanical analysis on the homogenizing treated alloy revealed that the tensile strength of the alloy was raised by the increased mass fraction of Zn.Alloys with Zn of 0%,1.5%,3%and 5%had tensile strength of 295MPa,355MPa,360MPa and 425MPa as well as ductility of 7.5%,5.5%,4.6%and 4.1%.Fracture analysis showed that ductile fracture dominated for the alloys homogenizing treated.(6)The alloy rolled with a descending distance 85%had grains with size less than 200nm.The grain size decreased with increasing Zn content,which is attributed to the raised work hardening rate.(7)A fter rolling process,the tensile strength of the alloy was raised remarkably.Alloys with Zn of 0%,1.5%,3%and 5%had tensile strength of 406MPa,495MPa,560MPa and 596MPa.Alloy with 5%Zn had tensile and yield strength of 596MPa and 567MPa which were almost double that of annealed 5083 aluminum alloy.Moreover,rolling process reduced the ductility of the alloy.(8)Dipping tests and electrochemical tests were conducted on the alloy in aqueous solution of NaCl with mass ratio of 0.035.The results showed that the corrosion resistance of the homogenizing treated alloy decreased with increasing Zn addition.Moreover,the rolled alloy showed an inferior corrosion resistance compared with the homogenizing treated one.