Microstructure And Properties Of Rolled AM60B Magnesium Alloy Sheet With High Strain Rate

Magnesium alloys are the lowest density metal materials used in industrial production.It has many outstanding advantages,such as high specific strength,high specific stiffness and good electromagnetic shielding performance.So it has been widely used in many fields,such as automobile industry,rail transit,electronic information and weapon equipment,especially in the field of lightweight machinery and equipment.It is known as"green metal material in 21st century".However,the intrinsic brittleness caused by dense hexagonal structure seriously hinders the further application of magnesium alloys.The poor plastic deformation ability is its fatal disadvantage.At the same time,sheet is the most important application medium form of magnesium alloy material in industrial production,and the demand for high quality magnesium alloy sheet in manufacturing industry is increasing year by year.But the traditional intermediate annealing assisted multi-pass low-pressure rolling process not only has low efficiency and high energy consumption,but also produces magnesium alloy sheet with poor mechanical properties,which can not meet the increasingly stringent requirements for mechanical properties in many fields.High strain rate rolling technology can raise efficiencyand produce magnesium alloy sheet with good mechanical properties by improving strain rate.Therefore,this paper proposes the preparation of magnesium alloy sheets with"both shape and property"by high strain rate rolling technology.The ultrafine lamellar structure was induced by high-strain rate with the attribute of near impact deformation,and the single-pass high-strain rate rolled sheet was strengthened.And the layered bimodal microstructure formed by alternating distribution of shear band and dynamic recrystallization was used to realize the strong and toughening of the double-pass high strain rate rolled sheet.Based on the as-cast AM60B magnesium alloy,the feasibility of single/double-pass high strain rate rolling was explored by designing the process parameters reasonably.The effective process path of increasing strain rate by controlling roll speed was found.The strain rate of single-pass rolling is increased to 6.75 s^-1.The detwinning behavior of high strain rate rolling and the enhancement effect of the formation of ultrafine lamellar structure on the sheet were clarified.In addtion,the temperature effect of microstructure and property evolution of sheet during annealing was revealed by studying the isothermal annealing behavior of sheet.A short-time low-temperature annealing process is found,which can make the sheet strong and tough.The tensile strength of sheet is 297 MPa after annealing for 1h in 160?.Three kinds of shear band formation mechanisms were also concluded by studying the whole process microstructure and performance evolution of cooling gradient double-pass high strain rate rolling process?shear band induced by lamellae ofcross twins,shear band induced by coupling coarse grain boundaries andthe lamellae of cross twins,shear band induced by grain boundary dynamic recrystallization?.The strengthen and toughening mechanism of sheet by the combination of layered bimodal microstructure and strong tendency of dynamic precipitation and weak basal texture was revealed.The AM60B magnesium alloy sheet with excellent comprehensive mechanical properties was prepared.The tensile strength of the sheet is 319 MPa.