Study On The Effects Of Cu And Mg Content On Microstructure And Properties Of 2024 Alloy

As an aircraft skin material,2024 aluminum alloy is required to have good mechanical properties,corrosion resistance and low chemical milling roughness.Due to the wide range of the main components（Cu,Mg）of the alloy,the change of the composition has a great influence on the comprehensive properties of the alloy.In this paper.The thermal deformation behavior of the alloy was studied and the effect of Cu and Mg content on the microstructure,mechanical properties,corrosion resistance and chemical milling properties of 2024 aluminum alloy,which was studied by different test methods,including tensile test,electrochemical test,IGC test and other methods.Finally,the hot deformation behavior of typical alloys was studied.The main conclusions and results are as follows:（1）With the content of Cu and Mg elements increasing,the segregation phenomenon in the as-cast microstructure becomes serious,and the volume fraction of the coarse crystalline phase in the alloy also increases.After solid-solution and artificial aging treatment,the precipitation phase of the alloy is S phase.The increase of Cu content is beneficial to increase the precipitation quantity of S phase;The content of Mg element is related to the size of S phase,When the content of Mg element in the alloy is high,the size of the lath-shaped S phase increases.（2）After artificial aging,when the Cu and Mg contents are 4.34wt.%and 1.49 wt.%,the comprehensive mechanical properties of the alloy are the best.The tensile strength,yield strength and elongation of the alloy are 476 MPa,341 MPa and 31.7%.（3）In 3.5 wt.%Na Cl solution,the E_corrof the alloy moves positively with the decrease of Cu content in the alloy,while the I_corrof the alloy decreases with the decrease of Mg content.Reducing the content of Cu and Mg elements in the alloy is beneficial to improving the corrosion resistance of the alloy.（4）The milling roughness is related to the size and distribution of the coarse second phase in the matrix.In chemical milling solutions,dealloying of second-phase particles causes Cu enrichment.During the hydrolysis reaction,the surrounding OH^-concentration is increased to accelerate the dissolution of the aluminum matrix.（5）Al-4.34 Cu-1.49 Mg（wt.%）alloy has positive strain rate sensitivity.Optimizing the hot rolling process of the alloy in combination with the hot working diagram and the existing rolling conditions.The temperature of the suitable processing area of the alloy is determined to be 330～450℃,and the strain rate is 0.01～0.45 s^-1...