Research On Mechanical Properties And Damping Capacities Of Fine-grained Mg-xZn-0.6Zr Magnesium Alloy Sheets

Magnesium alloys have been widely used to produce high performance lightweight damping structure parts as one of the key materials due to its advantages of low density,high specific strength and specific strength,effective electromagnetic shielding,nonmagnetic,especially its excellent damping capacity is preferable to other metal structural materials.However,due to the lower strength of the existing high damping magnesium alloys and the contradiction between damping capacity and mechanical properties,the application scope of the high damping magnesium alloys have been greatly restricted.Actually,there are many reports on the controlling methods of mechanical properties and damping capacity of magnesium alloys.However,the progress in the research of high strength and high damping magnesium alloys is slow.The purpose of this thesis is to explore a novel preparation method that can coordinate the strength and damping properties of magnesium alloys,in order to prepare high strength and high damping magnesium alloy sheets.Firstly,high strain rate rolling processing(HSRR)is used to produce Mg-0.6Zr alloy sheets with fine grain size.The effects of rolling strain rate on the microstructure,mechanical properties and damping capacity of the as-prepared sheets were investigated,so as to explore the feasibility of preparing fine-grain high strength and high damping magnesium alloys.On the basis of these results,the effects of Zn content on the microstructure,dynamic precipitation,texture,mechanical properties and damping capacities of Mg-xZn-0.6Zr(x=2,4,6wt.%)magnesium alloys are further investigated.The damping mechanisms of the fine-grained sheets and effects of nano-sized precipitates on the damping capacities are to be explored.(1)The effects of rolling strain rate on microstructure,mechanical properties and damping capacities of Mg-0.6Zr sheets were investigated.The results show that with increasing rolling strain rate,the recrystallization volume fraction and the recrystallization grain size increases,and the basal texture is weakened.Therefore,mechanical properties of sheet metal show a downward trend while the damping capacities is on the rise.Comprehensive mechanical properties of HSRRed Mg-0.6Zr alloys obviously superior to the Mg-0.6Zr sheet fabricated by others rolling technology,which can be ascribed to more significant fine-grain strengthening.And,due to higher density of movable dislocation and fewer dislocation tangle,the strain-dependent damping of the HSRRed Mg-0.6Zr sheets are superior to others wrought Mg-0.6Zr magnesium alloys which means fine-grained magnesium alloys with higher movable dislocation density can also produce high damping capacities.(2)The effects of Zn content on microstructure,mechanical properties and damping capacities of Mg-xZn-0.6Zr alloy sheets were investigated.The results show that with increasing of Zn content,the recrystallization volume fraction and grain size of the as-rolled Mg-xZn-0.6Zr sheets decreased,meanwhile,the density of the nanometer Mg-Zn phase increased obviously and the size of the precipitates increased slightly.Stronger strengthening effects of fine-grain and high density of dynamic precipitation phase significantly improve the comprehensive mechanical properties.The tensile strength,yield strength and elongation of Mg-xZn-0.6Zr sheet are 314Mpa,249Mpa and 20.4%when the content of Zn is 6wt.%.At the same time,the room-temperature damping capacity of the Mg-xZn-0.6Zr sheets exhibit excellent,mainly due to the activation of non basal slip system and the interaction between dislocation and nanometer precipitated phases.When the content of Zn is 6wt.%,the Mg-xZn-0.6Zr sheet exhibits excellent damping capacities,with the Q-" of 0.0036 at ε＝1 x10-3.The Mg-Zn-Zr sheets with high strength and high damping properties was obtained,and the contradiction between mechanical properties and damping properties of magnesium alloys was resolved.