Effect Of Composition Control On Crystallization Temperature Range And Properties Of Al-Mg-Mn Alloy

5xxx series aluminum alloys have been widely used in aerospace,machinery manufacturing,automobile manufacturing,military manufacturing,shipbuilding and daily life and other fields,because of their high specific strength,small specific gravity,good molding performance and corrosion resistance,etc.As the national strategies on"Carbon neutral"and"Emission peak"were put forward,energy conservation,emission reduction and green manufacturing are the future development direction of aluminum alloy sheets manufacture.High throughput continuous casting and rolling process（HTCCR）was more and more favored by researchers and manufacturers because of the characteristics of lower energy consumption,shorter processing,faster speed and lower cost.However,for 5xxx series aluminum alloys with relatively high magnesium content（such as AA5052alloy）,because of its large crystallization temperature range,easy to produce segregation and other defects,these alloys could not be processed by the HTCCR.In this paper,AA5052（Al-2.5Mg,mass fraction,%,the same below）alloys were used as the base alloy,and the combination of thermodynamic simulation（Pandat and JMat Pro software）and experimental verification was proposed to reduce the content of Mg and increase the content of Mn,in order to design a customized Al-Mg-Mn alloy with a small crystallization temperature range and ensure its strength and toughness,and the customized Al-Mg-Mn alloy would suitable for HTCCR.On this basis,the influence of Zr and Er on the microstructure and properties of the customized Al-Mg-Mn alloy sheets was further studied by means of DSC,OM,XRD,SEM,TEM,microhardness test,tensile test,electrochemical test,weight loss analysis and the corrosion properties of these alloys were explored.The main results showed that:Pandat and JMat Pro software were used to simulate a kind of Al-1.5Mg-0.8Mn alloy with similar strength to Al-2.5Mg alloy and lower crystallization temperature range（10.8℃）as compared with Al-2.5Mg alloy.The ultimate tensile strength and elongation of annealed Al-1.5Mg-0.8Mn and Al-2.5Mg alloy sheets were 287.7 MPa,6.96%and 285.2 MPa,6.89%,respectively,which were basically consistent with the simulation results.DSC analysis present that the crystallization temperature range of Al-1.5Mg-0.8Mn alloy was 12.7℃,which was lower than that of Al-2.5Mg alloy,which was also basically close to the simulation results.Subsequently,the effect of Zr and Er on the microstructure and tensile properties of the customized Al-1.5Mg-0.8Mn alloy sheet was studied.The results showed that when Zr content was 0.2 wt.%and Er content was 0.3 wt.%,the tensile strength of Al-1.5Mg-0.8Mn alloy sheet was increased into 320.5 MPa,which was 11.3%higher than that of the unalloyed Al-1.5Mg-0.8Mn alloy sheet.Meanwhile,the Al-1.5Mg-0.8Mn alloy with 0.2 wt.%Zr and 0.3 wt.%Er present an elongation of 6.75%.It was mainly due to the microstructure refinement and uniform precipitation of Al₃Zr（Er）nano-sized particles.On the other hand,the crystallization temperature range of Al-1.5Mg-0.8Mn-0.2Zr-0.3Er alloy was 10.1℃,which was very close to that of Al-1.5Mg-0.8Mn alloy.The results of electrochemical and weight loss experiments showed that the corrosion currents of Al-1.5Mg-0.8Mn,Al-2.5Mg and Al-1.5Mg-0.8Mn-0.2Zr-0.3Er alloys were 2.63×10^-7 A·cm^-2,4.44×10^-7 A·cm^-2 and 2.60×10^-7A·cm^-2 respectively.The weight loss rates of the alloys were 1.88 mg·cm^-2·h^-1,6.96 mg·cm^-2·h^-1 and2.35 mg·cm^-2·h^-1 respectively.The corrosion resistance of the designed alloys was slightly better than that of Al-2.5Mg alloy,but they were still in the same corrosion resistance grade.