Gradient Microstructure Control And Edge Cracking Inhibition Of Magnesium Alloy Based On Variable Thickness Cross Rolling

Magnesium alloy is widely used in aerospace,automobile industry and other fields because of its small density and high specific strength,and it has great use value and application prospects.Due to the fact that the magnesium alloy has a close-packed hexagonal crystal structure and poor plastic deformation ability,the magnesium alloy is prone to generate edge cracks during the rolling process,which affects the forming rate of the magnesium alloy strip.At the same time,the traditional flat rolling method can not effectively improve the internal microstructure of the magnesium alloy,can not effectively refine the grain size of the magnesium plate,and it is difficult to realize the gradient structure control.Based on plastic deformation theory and damage theory,this paper takes AZ31 deformed magnesium alloy as the research object,through the combination of finite element numerical simulation and rolling experiment,systematically analyzes the rolling deformation cracking behavior and damage evolution law of magnesium alloy,studies the grain refinement mechanism and microstructure gradient distribution mechanism of magnesium alloy,and reveals the microstructure evolution law of rolling process.The specific content is: based on the hot compression simulation experimental data,the hot deformation behavior of AZ31 magnesium alloy was analyzed,and the thermal deformation constitutive equation of magnesium alloy was established;according to the rolling characteristics of magnesium alloys,a mathematical model of hot rolling force in different rolling regions during the variable thickness rolling of magnesium alloys was established.Based on the MAS deformation theory,the hot rolling numerical simulation of AZ31 magnesium alloy under different rolling paths was carried out.The cross-rolling process was used to roll the strip into a dog-bone shape,and then the rolling direction was changed to realize the rolling with different reduction ratios in the thick zone at the edge and the thin zone at the middle of the strip.Analyze the gradient distribution and edge damage of the strips in different deformation regions after rolling in different regions with controlled reduction ratio,compare and analyze the advantages and disadvantages of variable thickness cross-rolling and ordinary flat rolling on the performance of the strips after rolling.Based on the research ideas of further thinning of AZ31 magnesium alloy,multipass rolling analysis of different rolling processes was carried out on magnesium alloy,and a relatively reasonable strip rolling process route was formulated by comparison.Based on the variable thickness rolling deformation theory,through the combination of finite element simulation and rolling experiments,the rolling plate was rolled into a magnesium alloy strip with different thicknesses in the middle and edge regions by using a variable thickness cross-rolling method to achieve different rolling reduction of the edge and middle of the strip,and analyzed the strip deformation and edge damage in different deformation regions after rolling in different regions with controlled reduction ratio.At the same time,the edge curve during the rolling process of variable thickness rolling was changed,and the influence of different edge curves of AZ31 magnesium alloy on the edge crack and microstructure gradient of magnesium alloy was analyzed,and compared and analyzed the effect of different edge curves with ordinary flat rolling and ordinary cross rolling on the edge damage and gradient structure regulation of magnesium alloy.