Study On The Properties And Microstructure Of Al-Cu-Mg Alloy By Sc Microalloying And Heat Treatment

The Al-Cu-Mg alloy series with 2xxx designation is a lightweight,high-st rength and ductile aluminum alloy used primarily in the aerospace industry for structural components such as aircraft fuselage skins and wing skins.In recent years,the development of the aerospace industry has put forward higher requirements for the performance of alloy materials,which requires the development of aluminium alloy materials with higher overall performance.This article uses Al-4.3Cu-1.6Mg（wt.%）alloy with high Mg content with and without Sc as the research material.Adopting multi-scale microstructure characterization methods,including atomic scale annular dark field imaging（ADF）in scanning transmission electron microscopy（STEM）,energy spectrum（SEM-EDS）in transmission electron microscopy（TEM）,electron backscatter diffraction（EBSD）in scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and differential thermal scanning calorimetry（DSC）,combined with microstructure analysis methods such as intergranular corrosion,electrochemical behavior,Vickers hardness,and tensile properties testing,The micro mechanism of traditional heat treatment process（T6 solid solution+aging）,heat treatment process parameters,and 0.2Sc（wt.%）addition improving the performance of Al-Cu-Mg alloy has been revealed.The results show that Sc microalloying limits the nucleation and coarsening of the S precipitated phase in Al-Cu-Mg alloys under T6 artificial ageing,resulting in smaller S phase sizes in Al-Cu-Mg alloys containing Sc.In addition,the Guinier-Preston-Bagaryatsky（GPB）zones,another important nanoscale precipitation phase in these alloys,was found to become smaller in diameter under the effect of Sc microalloying.The presence of Sc solute atoms was detected in the matrix of peak-aged Al-Cu-Mg-Sc alloys,and the formation of Al₃Sc nanoparticles limits the heterogeneous nucleation and growth of Al grains,inducing grain refinement,which is another important reason for alloy strengthening.The narrower grain boundary free zone（PFZ）and the coarse and discontinuous grain boundary precipitates（GBPs）improve the corrosion resistance of the Al-Cu-Mg-Sc alloy.Thus,the T6 state of Al-Cu-Mg-Sc alloys improve their elongation,corrosion resistance and ageing thermal stability while maintaining good yield and tensile strengths.In addition,based on the Vickers hardness,the heat treatment process of Al-Cu-Mg and Al-Cu-Mg-Sc alloys with solid solution parameters,natural aging,re-solution and re-aging was explored and found that the heat treatment process has some reference value for aluminium alloy design:the effect of solid solution time on the alloy properties is not obvious,the hardness increases with increasing solid solution temperature,but it is already over-burned at 540°C;Sc addition These findings have important implications for potential strategies to design high performance aluminium alloys through the addition of Sc and heat treatment processes.