Study On Microstructure And Properties Of Al-10Mg-1.0Zn-0.15Cu Aluminum Alloy

5xxx series aluminum alloy takes Mg as the main alloy element,which has low density,good corrosion resistance and weldability.It is widely used in automobile,ships,aerospace and other fields.The alloy mainly obtains the necessary strength through solid solution strengthening and work hardening.It cannot obtain the effect of aging strengthening through aging treatment.On the contrary,it usually precipitates coarse second phase in chain or network distribution during aging,which seriously affects the strength and plasticity of the alloy.At present,the content of Mg in 5xxx series aluminum alloy is about 3～5 wt%in industry field.With the increase of Mg content,the coarse Al₃Mg₂phase precipitated more easily.It seriously affects the strength and plasticity of the alloy.Therefore,how to increase the Mg content to obtain high strength after rolling and annealing,meanwhile avoiding the precipitation of coarse Al₃Mg₂phase or changing its morphology,is of great significance to the industrial application of high Mg content Al-Mg alloy.In this work,based on binary Al-10Mg alloy,the alloy with high Mg content was prepared by rapid solidification process and vacuum melting process.Through the comparison of two processes,the vacuum melting process is optimized to prepare the alloy for in-depth exploration.Through simulation calculation,1.0 wt%Zn and 0.15wt%Cu elements are added to obtain the alloy with Zn/Mg ratio much lower than 2.0,which is significantly different from the traditional 5xxx and 7xxx alloys in composition.The alloy with high yield strength and tensile strength is obtained by solution treatment and rolling,and then the strength and plasticity of the alloy are adjusted by annealing at different temperatures to obtain Al-10Mg-1.0Zn-0.15Cu alloy with high strength and plasticity.This work focuses on obtaining alloy with good strength,plasticity and corrosion resistance.The strengthening and ductility mechanism of new alloy is analysed by tensile test,hardness test,electrochemical test,X-ray diffraction analysis,scanning and transmission structure characterization,the strengthening mechanism of the new alloy mainly contributed by solution strengthening,grain boundary strengthening,dislocation strengthening and precipitation strengthening.And clarify that the addition of Zn and Cu elements changed the formation of coarse precipitates in the annealing process of binary Al-Mg alloy,the corrosion resistance mechanism of the new alloy is clarified.It is found that the solid solution process of Al-10Mg-1.0Zn-0.15Cu alloy is440℃×9h,at this state,the yield strength and tensile strength are 191 MPa and 352MPa,and the uniform elongation is 21.9%.After rolling～75%at room temperature,the yield strength reaches 536 MPa while the uniform elongation decreases sharply to～6.3%.After annealing at 150℃,the nanoscale precipitates in the alloy take the effect of precipitation strengthening.The yield strength is 519 MPa,tensile strength is 653MPa and the uniform elongation is 8.1%.According to the microstructure characterization of transmission electron microscope,Spherical granular or short rod precipitates are precipitated in the grains.Combined with the analysis of selected area electron diffraction pattern and energy spectrum results,it is confirmed that the precipitated phase is T-Mg₃₂（Al,Zn）₄₉phase.The addition of Zn and Cu element promoted the precipitation of T-Mg₃₂（Al,Zn）₄₉phase and inhibited the precipitation of Al₃Mg₂phase.After solution quenching,the alloy produces a large number of quenching vacancies,and the subsequent deformation treatment produces high-density dislocations,resulting in the formation of Mg-vacancy pair clusters at the grain boundary.Because the diffusion speed of Zn is faster than Cu,Zn preferentially combines with Mg-vacancy pair clusters to form Mg-Zn clusters.At the same time,based on the interfacial adsorption effect,Mg,Zn and Cu atoms are continuously absorbed,and then further grown and finally transformed into T phase.5083 aluminum alloy is widely used in industry field.The corrosion resistance of Al-10Mg-1.0Zn-0.15Cu alloy prepared in this work is compared with that of 5083aluminum alloy.When 5083 aluminum alloy is treated to the same rolling state of the alloy prepared in this work,the polarization curves show that the corrosion potential and corrosion current density of the two alloys are similar,which are-0.996 V and-0.981 V respectively,and the corrosion current density are 0.389 m A·cm^-2and 0.347m A·cm^-2respectively.After annealing treatment,the corrosion potential of Al-10Mg-1.0Zn-0.15Cu alloy increases,the corrosion current density decreases,and the corrosion resistance of the alloy is further improved.