| At present,the production of aluminum alloys mainly adopts the method of the open billet hot rolling,but this process has a long production cycle,high cost,and high pollution.The high-throughput continuous casting and rolling process has the advantages of short process flow,low cost,and low pollution.This is a new and efficient aluminum plate production process,and it has been used in the production of pure aluminum and 3xxx series aluminum alloys.while the Mg content is relatively high in 5xxx aluminum alloys,and the crystallization temperature interval is relatively large.When high-throughput continuous casting and rolling process is used to produce5xxx aluminum alloys,because of its fast cooling rate,the existence of solid-liquid two-phase zone is further prolonged,which is easy to produce inclusions,segregation,and other defects,the surface quality of the sheet is poor.Therefore,this paper intends to use the method of microalloying to study a 5xxx aluminum alloy with relatively a low crystallization temperature interval while excellent mechanical properties and corrosion properties,which can be applied to produced by continuous casting and rolling.Through OM,DSC,XRD,SEM,EBSD,TEM,XPS,etc.microstructure observation methods,room temperature tensile test,cupping test,exfoliation corrosion test,and intergranular corrosion test,etc.testing and analysis methods to explore the effects of compound addition of Zn,Si,Zr and Ti on the crystallization temperature range,microstructure,mechanical properties and corrosion properties of Al-2Mg-0.5Mn alloy.The main conclusions are as follows:The DSC test results of the as-cast alloy show that the composite addition of Zn and Si to Al-2Mg-0.5Mn reduces the crystallization temperature interval of the alloy by 2.2℃,while the composite addition of other alloy elements slightly increases the crystallization temperature interval of the alloy,but the overall difference is not much.The microstructure and microhardness results of the as-cast and homogenized alloys show that the composite addition of alloying elements improves the microhardness of the as-cast and homogenized alloys to varying degrees,and the microhardness of the composite-added Ti-containing alloy increases the most obvious.The compound addition of Zn and Ti,Si and Ti significantly refine the as-cast and homogenized grains of Al-2Mg-0.5Mn alloy.After adding trace elements,the second phase precipitated increased significantly,and the corresponding Mg Zn2,Mg2Si,Al3Zr,and Al3Ti phases were formed in the alloy.After homogenization,the dendrites in the alloy are eliminated,and the second phase is evenly dispersed along the grain boundary,but there are still a small number of dendrites in the alloys with composite addition of Zn and Ti,Si and Ti.The microstructure observation of the alloys after cold rolling shows that the grain structure of the alloys is liked fibrous,and the composite addition of Zn and Ti,Si and Ti significantly refines the fibrous structure of the alloys.The alloys after rolling mainly contains S{123}<634>texture,Brass{110}<112>texture,Copper{112}<111>texture and Goss{110}<001>texture.Among them,the content of Brass texture in Al-2Mg-0.5Mn alloy is the most.After adding alloying elements,the Brass texture is reduced,and the S texture is increased to the most.The grain boundaries of cold-rolled alloys are mainly low-angle grain boundaries,and a small amount of high-angle grain boundaries and sub-grain boundaries.The grain types of cold-rolled alloys are mainly deformed grains(>91%).The alloys have a high density of dislocations after cold rolling,and a large number of dislocations are entangled with each other to form the boundary of the cellular substructure.The mechanical properties of the alloys after rolling show that the composite addition of alloying elements to the Al-2Mg-0.5Mn alloy can effectively improve its microhardness and ultimate tensile strength,and the composite addition of Zn and Ti,Si and Ti alloy as strength and hardness increases,its elongation also increases.Composite addition of Zn and Ti,Si and Ti also improved the forming performance of Al-2Mg-0.5Mn alloy,while other combination alloy elements slightly reduced the forming performance of Al-2Mg-0.5Mn alloy.The corrosion test results of the alloys after rolling show that after the nitric acid weight loss experiment,the unit mass loss of the rolled plates all are between 1 and 3.5mg/cm~2,which are all alloys with resistance to intergranular corrosion.The polarization curve test of the alloy shows that after adding alloying elements to the Al-2Mg-0.5Mn alloy,while the self-corrosion potential of the alloy increases,the corrosion current density decreases slightly,and the electrochemical corrosion resistance is improved.The exfoliation corrosion grade of the alloy after rolling is P grade,no exfoliation corrosion occurs.The compound addition of alloying elements improves the exfoliation corrosion resistance of the alloy to varying degrees,and the compound addition of Zn and Zr has the most obvious effect.The improvement of corrosion resistance after the composite addition of trace alloying elements to the Al-2Mg-0.5Mn alloy is mainly related to the refinement of the grain size. |
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