Research On The Effects Of Alloying Elements On Damping Capacities Of Magnesium Alloy And Its Mechanisms

Magnesium alloys have the advantages of low density,high specific strength and specific modulus and good damping capacities,the addition of alloying elements is the main means to improve the damping capacities and mechanical properties of magnesium alloys.Up to now,the research on the damping capacities of magnesium alloys are mainly focused on the development of new magnesium alloy systems,the exploration of material preparation technologies(casting,plastic processing)and the correlation between heat treatment processes and micro structure characteristics and damping capacities of materials.However,there are few reports on the effects and mechanisms of the types of alloying elements on the damping capacities of magnesium alloys with the same element content.In this paper,the effects of alloying elements on damping capacities and mechanical properties of four Mg-lat%X binary alloys(X=Zn,Sn,Ga,Al)are carefully investigated with pure Mg as comparison,and its mechanism was revealed.In this paper,the effects of solute atomic characteristics on the damping capacities of magnesium alloys were systematically investigated by solution treatment.The effects of alloying elements on recrystallization,mechanical properties and damping capacities of wrought magnesium alloy were studied by hot compression simulation experiment and high strain rate rolling(HSRR).The effects of pre-deformation on the mechanical properties and damping capacities of different systems of magnesium alloys were investigated by the combination of pre-deformation process and HSRR.The effects of four alloying elements on the microstructure and damping capacities of as-cast and solid solution Mg-1at%X alloys were firstly studied.The research shows that:Among the four as-cast alloys,the Mg-1at%Sn alloy has the best damping capacity,while the Mg-1at%Zn alloy has the worst damping capacity.After solution treatment,all the alloying elements exist in the form of solute atoms in the magnesium matrix.Because the grain sizes and atomic percentages of the four alloys are the same,the mechanical properties and damping capacities of solid solution alloys are mainly related to the characteristics of solute atoms.At room temperature,the strain-amplitude-independent damping capacity of the solid solution alloy decreases with the higher lattice distortion caused by solute atoms,while the yield strength is just the opposite.The strain-amplitude-dependent damping capacity is affected by the lattice distortion,the stacking fault energy and the mixing enthalpy between solute atoms and Mg atoms,while the stacking fault energy is the dominant.The higher the stacking fault energy of the alloy is,the better the strain-amplitude-dependent damping capacity is.When the temperature rises to about 100℃,the strain-amplitude-independent damping capacity of the solid solution alloy increased with the higher lattice distortion.This may be related to the increase of the dynamic force for dislocation bowing caused by thermal activation.In this paper,the effects of alloying elements on the hot compression deformation behavior of Mg-lat%X alloy and the micro structure,recrystallization behavior,damping capacities and mechanical properties of HSRRed sheet were studied.The research shows that:The DRX volume fraction and the DRX critical strain of the alloys are related to the stacking fault energy,the difference of electronegativity and mixing enthalpy between the alloy elements and Mg,and the stacking fault energy is the main factor.The DRX volume fraction increases at first and then decreases with the decrease of stacking fault energy,and the critical strain of DRX decreases at first and then increases with the decrease of stacking fault energy.The Mg-1at%Ga alloy has the highest volume fraction of DRX(95%),the smallest critical strain of DRX(0.24)and the biggest elongation(35.2%).The Mg-lat%Al alloy has the best comprehensive mechanical properties,with YTS of 210 MPa,UTS of 247 MPa,El of 19.8%.All the as-studied alloys are high damping magnesium alloys.The damping capacity of the as-rolled alloys decreases at first and then increases with the increase of the DRX volume fraction.And when the degree of DRX is very high,the DRX grain size will become the key factor affecting the damping capacities of the alloys.The temperature damping curves are featured with two damping peaks for all the alloys and the P1 peak associated with grain boundary relaxation is in connection with the DRX volume fraction and grain boundary energy.The effects of pre-deformation on the mechanical properties of different systems of magnesium alloys are different.The pre-deformation has the greatest effect on the yield strength of Mg-lat%Ga and the elongation of Mg-lat%Sn alloy.The pre-deformation reduces the strain-amplitude-independent damping capacities of as-rolled magnesium alloy sheets,and improves the strain-amplitude-dependent damping capacities of other alloy sheets except Mg-lat%Al alloy.