| With the increasing maturity of continuous extrusion forming technology,the market demand for AZ31 magnesium alloy plate gradually increases.Using continuous extrusion technology to prepare magnesium alloy plate can not only save energy,but also be conducive to industrial production and have technological innovation.The production method of double-rod or even multi-rod feeding can increase the aspect ratio of the sheet.However,the use of continuous extrusion technology to expand the formation of large width-thickness ratio plates may occur defects such as waves and flash.Therefore,based on the continuous extrusion technology,it is not only innovative but also challenging to study the forming process of large-width-to-thickness magnesium alloy sheets by different methods.Based on the continuous extrusion process of AZ31 magnesium alloy,the numerical simulation of continuous extrusion sheet and profile forming process was carried out by HyperXtrude finite element simulation software based on TLJ400 and TLJ630 continuous extruder,and AZ31 magnesium alloy sheets with width to thickness ratio of 20 and 60 were obtained by continuous extrusion experiments,combined with the microstructure analysis technology,the characteristics of different extrusion processes,the metal flow law and its influence on microstructure were studied.The distribution law of each physical field during the horizontal expansion forming of double-bar continuous extrusion sheet and circumferential expansion forming of single rod continuous extrusion C-shaped,and the evolution of microstructure during forming process were analyzed.The research results are as follows:During the forming process of the double-rod continuous extrusion magnesium alloy sheet,the metal in the cavity flows laterally while flowing forward.In the direction of extrusion,the metal has the fastest flow rate at the right-angle bending zone.There are bimodal phenomena in the distribution of temperature,velocity and strain fields in the confluent and extended cavities.When the metal flows into the welding chamber,the double peak phenomenon of the velocity field and the temperature field disappears due to the welding action,and the distribution of the strain field still has a double peak phenomenon.The cross-sectional grain size increases gradually from the blank inlet to the die exit at different regions of the mold cavity,which is related to the gradual decrease in the pressure value from the blank inlet to the die exit in the cavity.Circumferential expansion forming process of single-rod continuous extrusion C-profile,the distribution of the temperature and velocity field of the C-profile at the exit of the die appears to decrease from the central region of the profile to the edge regions on both sides.The distribution of the strain field is exactly the opposite of the distribution of temperature and velocity fields.C-profile forming experiment was carried out with simulated parameters,and the obtained C-profile has good appearance quality.Metallographic microstructure analysis of cross section of C-profile can be concluded that velocity streamline is in the 45mm region on both sides of the cross section of the C-profile,and there is a metal layer color stratification in the region of 120mm in the center of the profile.The grain size of the cross-section of the C-profile is gradually increased from the edge regions on both sides to the center of the profile.The specification of the plate prepared by the double-rod continuous extrusion expansion forming method is 160mmx8mm,aspect ratio is 20.The specification of the sheet prepared by the process of flattening the C-profile continuously extruded by a single-rod is 240 mm×4 mm.aspect ratio is 20.Through experimental verification,the combination of continuous extrusion process and rolling flattening process makes it easier to prepare large width-thickness ratio plates,and the appearance quality of the obtained plates is better. |
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