Research On Microstructures And Properties Of Medium-thickness Sheets Of AZ31 Magnesium Alloy

Magnesium alloy sheet is characterized by its light weight,high specific strength and good damping performance.It has broad application prospects in large-scale vibration platforms and aerospace industries.In order to meet the requirements of large-scale aerospace industry and structural components,it is necessary to further improve the uniformity of microstructures and properties of magnesium alloy medium-thickness sheet.At the same time,the anisotropy of the mechanical properties is caused by the presence of the texture of the rolled magnesium alloy.Therefore,this paper focused on the hot-rolled AZ31 magnesium alloy sheet,and studied the grain size,microstructure uniformity,recrystallization degree,texture type,strength and mechanical property uniformity of the medium-thick sheet of the alloy,the influence of microstructure on mechanical propertiesis also discussed.The main conclusions are as follows:The microstructure of AZ31 magnesium alloy prepared by different deformation amounts has a large difference.The average grain size from the surface layer to the center of the plate gradually increases.As the deformation amount increases,the average grain size decreases,and the difference of average grain size from surface layer to center also decreases..For a sheet material with a deformation of 72%,the surface layer and the central area are composed of equiaxed crystals and fibrous grains.The change of the equiaxed crystals from the surface to the center gradually changes from relatively fine and uniform grains to coarse grains.The change pattern of fibrous crystals from the surface layer to the center gradually changes from a small number of slender fibrous crystal grains to coarse fibrous crystal grains.For the plates with a deformation amount of 97%,they are all small and uniform equiaxed crystals.The difference between the surface layer and the central region is not large,and the average grain size is 9.9 μm.The degree of recrystallization in different regions of the plate is also different under different deformation amounts.When the amount of deformation is small,the proportion of recrystallized grains is small.As the amount of deformation increases,the proportion of recrystallized grains increases.Under the same amount of deformation,the degree of recrystallization from the surface layer to the center gradually decreases;under a larger amount of deformation,the degree of recrystallization in different regions is larger and becomes more uniform.When the amount of deformation is 97%,the proportion of recrystallized grains in the plate reaches 70～80%.Under different deformation amounts,the sheet even exhibits {0002} basal texture,and as the deformation increases,the basal texture of the sheet weakens;the texture strength of the central area of the plate is higher than the surface layer,and the deformation is particularly prominent when the deformation is small.As the amount of deformation increases,the texture strength in the central area decreases sharply,and the surface strength decreases slowly;the surface texture strength decreases from 15.03 at 72%deformation to 8.92 at 97%,while that in the central texture strength decreases from 23.36 at 72%to 11.22 at 97%,Deformation has a significant effect on the mechanical properties of AZ31 magnesium alloy sheet in different directions and at different positions.When the amount of deformation is small,the mechanical properties of the sheet in different directions are anisotropic.The mechanical properties of the lateral sheet are slightly higher than longitudinal sheet,while the thickness direction performance is worst.The AZ31 sheet with a thickness of 100mm differs by 92 MPa of yield strength in the vertical and thickness direction.The mechanical properties in the surface area of the sheet are higher than those in the center of the sheet.With the increase of the deformation,the comprehensive mechanical properties of the sheet are enhanced,in addition the properties between surface and center are uniformvand and the anisotropy decreases.The performance is reduced.The transverse and longitudinal tensile strength,yiled strength and elognation at the surface area of the medium-thickness sheet with a deformation of 97%are 269 MPa,265 MPa,178 MPa,176 MPa,20.2%and 19.1%,respectively.