Research On Hot Rolling Process And Prediction Model Of Microstructure And Mechanical Property For Cast-rolling AZ31B Magnesium Alloy Sheet

Magnesium alloy sheets with better microstructure and properties can be produced by rolling processing technology. However, existing rolling technology of magnesium alloy plate and strip lacks theoretical guidance. The rolling processing technology has many problems, such as multiple passes,instability of the slab quality and the edge crack. At present, the research for influence of rolling process on the evolution mechanism of microstructure and properties are not perfect. The forecast work of microstructure and properties for rolling plastic deformation of magnesium alloy is not further developed, and the mechanism model of characterizing the relationship between the microstructure and properties for rolled sheet is not further studied. Therefore,based on the theoretical researches and rolling experiments, the effects of rolling process on microstructure and properties of magnesium alloy sheets should be systematically studied, and the evolution mechanism of microstructure and properties during plastic deformation also should be intensively studied. These studies will be full of practical significance.In this paper, based on the topic idea of further thinning rolling for AZ31 B magnesium alloy cast-rolling plate, single-pass hot rolling experiments and multi-pass hot rolling experiments of different routes were conducted. By analyzing the experimental data of the microstructure and properties of the hot-rolled magnesium alloy sheets under the wide-range condition of single-pass rolling, the effects of rolling reduction, rolling speed and initial rolling temperature on the microstructure and mechanical properties were emphatically studied, and the correlation between the rolling process parameters and microstructure evolution, macro mechanical properties was revealed. Then the accurate strain rate model of rolling deformation zone was established by using exact contact-arc equation and its parameter equation. Based on Zener-Hollomon parameter and the analysis of the correlation between the average grain size and hot rolling process parameters, the prediction model of average grain size for the rolled magnesium alloy sheet was established.Combined with the tensile strength model, the prediction model of microstructure and mechanical properties of hot-rolled AZ31 B magnesium alloy sheet was achieved, and the error analysis of the model was carried out.Bidirectional guidance between hot rolling process and microstructure and properties is provided by this model. Based on the experiment of four different rolling routes at the initial rolling temperature of 250~400 ℃, the effects of rolling temperature and rolling routes on microstructure and mechanical properties were comprehensively studied. Based on the Hall-Petch relation, and considering the average grain size and grain distribution, grain distribution coefficient d CV was introduced, and the nonlinear fitting analysis between the tensile strength and average grain size was carried on, then the prediction model of tensile strength of hot-rolled AZ31 B magnesium alloy sheet was established.Ultimately, the close relationship between microstructure and mechanical properties of AZ31 B magnesium alloy is further revealed.