Effect Of Sn Content On Microstructure And Damping Properties Of Mg-Al-Zn Magnesium Alloy

To develop high-strength damping magnesium materials which would be generally used in industrial field.The work prepared Mg-3Al-1Zn(AZ31),Mg-3Al-1Zn-3Sn,Mg-3Al-1Zn-6Sn,Mg-3Al-1Zn-9Sn in four Sn content by using die-cast process.Then these die-cast alloys were characterized by X-Ray Diffractometer(XRD),Scanning Electron Microscope(SEM),and Electron Back Scatter Diffraction(EBSD)technology.The mechanical properties and damping behavior of the four die-cast alloys were systematically studied.The Sn addition in commercial AZ31 die-cast alloy makes the big grains and small grains mixed organization structure of Mg-3Al-1Zn-x Sn(x=0,3,6,9 wt.%)alloy more uniform and the grain refined.The number of Mg2 Sn precipitation phases also increases as well as the Sn added.The enrichment of Mg2 Sn at grain boundary not only inhibits the nucleation and growth of the Mg17Al12 precipitate phase effectively but also hinders the movement of dislocation.Grain refinement and precipitation strengthening were two main strengthen mechanism in the alloy.However,when the Sn was added too excessively,the Mg2 Sn precipitation phases will coarsen and play a nucleus of microcracks,inducing the elongation of the alloy.The work analyzed the damping mechanism of die-cast Mg-3Al-1Zn-x Sn(x=0,3,6,9 wt.%)alloys by using Dynamic Mechanical Thermal Analyzer(DMA).It turned out that the alloy's damping property was improved greatly after the Sn added.The alloy's damping mechanism was divided into two main stages: The damping mechanism in the elastic damping stage is the dislocation damping mechanism;the damping property in the microplastic deformation stage is due to the frequency-dependent microplastic damping mechanism.The damping value of the alloy will increase rapidly when entering the microplastic deformation stage.The contribution of the damping to the alloy mainly comes from three aspects: unstable tension twin formed during the vibration,the alloy's softening due to dynamic recrystallization,and the activation of non-basal slip systems causes quantities movable dislocations.