Effect Of Rolling Process On Texture And Mechanical Properties Of Mg-4Zn-1Gd Magnesium Alloy Sheet

Magnesium alloy has the characteristics of light weight,high specific strength and high specific stiffness,and can be used to enhance weight loss in the fields of transportation and aerospace.However,due to the low sliding system of magnesium alloy,it is easy to form a strong basal surface texture when deformed at low temperature or room temperature,resulting in low ductility and strong anisotropy,which is not conducive to processing and molding.At present,the main methods for improving the forming performance of magnesium alloy sheets include: increasing the temperature,refining the grains,and improving the texture.Adding Ca or rare earth element Gd to the magnesium alloy can achieve the purpose of regulating texture and refining grains,thereby effectively improving room temperature ductility and formability.In addition,the rare earth magnesium alloy with weak initial texture can effectively adjust the texture type by changing the rolling method,thereby weakening the anisotropy of the sheet and improving the forming performance.In this paper,Mg-4Zn-1Gd magnesium alloy is taken as the research object.The unidirectional rolling and cross rolling tests are carried out at two temperatures(400℃ and 300℃),and the modern microscopic analysis method is used to systematically study the rolling The influence of technology on the microstructure,texture and mechanical properties of alloy sheets provides theoretical guidance for optimizing the rolling process of magnesium alloys.The main research conclusions of the paper are as follows:(1)When the hot rolling temperature is 400℃,the degree of recrystallization is high,and the recrystallized grains grow fast,and the grains are coarse after rolling.When the hot rolling temperature is reduced to 300℃,the proportion of dynamic recrystallization is small,and the grains are fine after rolling.Compared with unidirectional rolling,the cross rolling deformation is more uniform and the grain size is more uniform.(2)The unidirectionally rolled sheet is affected by the main tensile strain direction on the deformation mechanism and dynamic recrystallization behavior,forming a bimodal texture with texture peak strength biased to RD or TD;cross-rolling is due to the main tensile strain direction during rolling Alternating changes during the manufacturing process,forming a circular texture.(3)After annealing,the unidirectionally rolled sheet forms a TD weak texture,and the cross-rolled sheet forms an annular weak texture.The nucleation stage of the recrystallized grains affects the c-axis orientation of the grains,resulting in initial recrystallized grains mainly distributed along the TD or ring shape,while weakening the texture strength,and the growth stage of the recrystallized grains will not change the plate Texture type.(4)The size of the deformed grains in the hot-rolled sheet will affect the grain size during the subsequent static recrystallization annealing.The deformed grain size of the high-temperature rolled sheet is coarse,the specific surface area of the grain boundary is small,the nucleation site at the grain boundary is reduced,and the size of the recrystallized grain after annealing is also large.Conversely,annealing and recrystallization grains are finer.(5)Compared with unidirectional rolling,cross rolling has better comprehensive mechanical properties and lower anisotropy.The magnesium alloy sheet mainly slips on the base surface when it is stretched at room temperature.During unidirectional rolling,the Schmidt factor in the RD direction,45° direction from RD,and the TD direction is quite different,so the time base is stretched in different directions The difference between the ease of starting and the activation activity of the surface slip leads to the difference in yield anisotropy;the Schmidt factor in the three directions of cross-rolling differs little,and the anisotropy of mechanical properties decreases.The tensile fracture structure shows that cross rolling produces more dimples than unidirectional rolling,and the dimples are deeper,indicating that it has higher plasticity and coordinates more deformation during the tensile fracture.