Researches On The Rolling Of Magnesium Alloy Sheet And Simulation

Wrought magnesium alloy sheet has been widely used in many fields, just as vehicle, electronic products and automotive. Rolling is the primary method to get magnesium alloy sheets. However, magnesium alloy possesses poor formability at room temperature because of its hexagonal closed packed (HCP) crystal structure and little slip system, and processed yield is low, edge cracks easily appear in production process, these phenomena led to high price of magnesium alloy sheets, which could limit its wild application. So, research on rolling process and simulation of magnesium alloy sheet has significant theoretical meaning and engineering value for increasing the production efficiency, improving the mechanical property and reducing production cost.In this paper, AZ31 magnesium alloy was chosen to investigate, the thermal deformation and the rolling processes of AZ31 magnesium alloy were studied with microscopic examination, SEM and XRD, and so on. Physics and numerical simulation technique such as Gleeble-1500 thermal analog computer and Marc software were also employed.The flow stress features of AZ31 magnesium alloy were studied by isothermal compression of cylindrical specimens at 200~400℃and strain rate of 0.01~10s-1 with Gleeble-1500 material simulation machine. The results showed that the flow stress increased with the increase of strain rate and decreased with the increase of deformation temperature. Flow stress curves obtained from experiments were composed of four different stages, work hardening, transition, softening and steady stages. The flow stress of AZ31 magnesium alloy during high temperature deformation process could be represented by Zener-Hollomon parameter including the Arrhenius term and the constitutive equation was acquired. The microstructure under different deformation conditions was analyzed, taking another factor as the result of unbiaxial stretch experiment, it was considered that the good deformation condition is temperature of 350~400℃with strain rate 0.01~0.1s-1.By using finite element numerical simulation, the rolling process of magnesium alloy was stimulated, and the equivalent stress, temperature and spread were analysed. Results showed that when temperature was down below 210℃, edge crack took place, and it was the limit to roll.The maximum stress was located at the edges of the sheet, and the spread of the head and the end of sheet were larger. The property of AZ31 magnesium alloy was obtained, which provided a proof for the development of sheet rolling technology of magnesium alloy.The influence of rolling reduction and plate width on microstructure and property of AZ31 magnesium alloy was studied by the cuneal sheet and trapezium sheet; the influence of rolling temperature and pass reduction was also studied by rectangle sheet, the boundary conditions when edge cracks appear were obtained, the limit of pass processing rate during hot rolling could reach 62.5% when rolled at 400℃, pass reduction was 1mm; taking another factor as the result of microhardness, SEMand XRD, the reasons for appearance of edge cracks were analysed; finally, compression test simulate the generation process of cracks.