Technology Research On Cross Rolling Of The AZ31 Magnesium Alloy

Magnesium alloys are the lightest structure materials for the practical engineering applications. They have many outstanding physical, chemical and mechanical properties, and have been widely used in electronics, electrical, automobile, aerial and astronautical industries. Now the plastic forming technology of Mg alloys is still in development stage, meanwhile rolling is a very important orientation in this area. Cross rolling process for AZ31 Mg alloy is studied in this paper in order to discuss the anisotropy of the rolled sheets.In this dissertation, FE analysis of one-way rolling was carried out to determine the reasonable rolling process parameters. The FE analysis of cross rolling was to show the difference of extreme value of plastic strain in one-way rolling was smaller than that in cross rolling with the same pass and the same reduction, therefore, it was proved that the cross rolling process could reduce the anisotropy of the Mg alloy sheet.Designed and transformed for the existing oneФ90/200×200 mill in laboratory with the aim was to change the old mill into a new 4-roll synchronous, asymmetrical reversible rolling mill. Design of gears, gear shafts, housings, box in gear case were the main tasks, the structural design of the other part of the mill were also included. Heating device for rollers was installed by the reason of Mg alloys had low formability at room temperature. Last, the new mill was set up and tested .Microstructure and mechanical properties of AZ31 Mg alloy sheets were investigated in rolling experiments. The results showed that the optimum heat-treatment process was 300℃×30min. The shape of microstructure in larger reduction of rolling process to be more uniform when the sheets had equal deformation in final and rollers at heating state. Because the two ways got the same results in refinement between one-way rolling and cross rolling, mechanical properties would be test further, the results showed that the cross rolling process could reduce the anisotropy and lower the yield stress and strength of the Mg alloy sheet.