Defect Analysis And Annealing Process Optimization Of Cast-Rolled Al-Mn-Mg Alloy Sheets

Al-Mn alloys are the best aluminium alloys in terms of corrosion resistance,moderate strength,deep-drawn forming properties and corrosion resistance,and are used in a wide range of applications,mainly in electronics,automotive,construction,aerospace and other industries.In the sheet production industry,casting and rolling of high quality aluminium alloys with high alloy composition is becoming more and more important,but some of the Al-Mn alloys currently produced in the industry have to be improved and have certain defects in their microstructure.In this thesis,Al-Mn-Mg alloy is used as the object of study.The casting and rolling process of Al-Mn-Mg alloy sheets at different casting and rolling temperatures and speeds is numerically simulated using Procast software to optimise the casting and rolling process.The subsequent annealing process of the prepared Al-Mn-Mg alloy sheets was studied to analyze the effects of annealing temperature and annealing holding time on the microstructure and mechanical properties of Al-Mn-Mg alloy sheets,and the main findings were as follows:Numerical simulations of the casting and rolling process of existing Al-Mn-Mg alloy sheets were carried out using the Procast software.The problem of inadequate billet forming during the casting and rolling process leading to reduced roll life was observed.The changes of temperature field and solid phase rate during the casting and rolling process were investigated for casting and rolling temperatures of 660,680 and700°C and casting and rolling speeds of 1,1.5 and 2 m/min respectively,and the optimum casting and rolling temperature was finally determined to be 680°C and the optimum casting and rolling speed should be controlled to be 1.5 m/min.Procast software was used to investigate the segregation of elements on the surface of Al-Mn-Mg alloys during the casting and rolling process,and it was determined that the black spot defects in the preparation process were caused by the segregation of Mg elements,and that reducing the content of Mg elements could effectively reduce the appearance of black spot defects without affecting the overall performance of the material.The microstructure and mechanical properties of Al-Mn-Mg alloy sheets were studied at annealing temperatures of 250,300,350 and 400°C.When the annealing temperature was 350°C,Al-Mn-Mg alloy sheets showed better isotropy than the other annealing temperatures,and the prepared sheets had small internal grains with uniform distribution.The optimum annealing temperature was determined to be 350°C.The changes in the structure and mechanical properties of Al-Mn-Mg alloy sheets were studied at annealing holding times of 1,2,3 and 4 h.When the holding time was 4 h,Al-Mn-Mg alloy sheets showed more excellent isotropy,and the internal grains of the prepared sheets were small and uniformly distributed,so the optimum annealing holding time was determined to be 4 h.