Microstructure,Mechanical,and Damping Properties Of Mg-Sn Alloy

With the rapid development of modern industry,vibration and noise have become serious problems.Whether in national defense or civil industry,weight reduction,vibration,and noise reduction have become the key to improving the reliability and stability of various instruments and equipment.The new materials for structural lightweight and vibration and noise reduction will be an important development direction of materials in the future.Magnesium and its alloys are not only low density,high specific strength,and specific stiffness,but also one of the structural metal materials with the best damping performance.At present,the main problem restricting the popularization and application of damping magnesium alloys is the contradiction between mechanical properties and damping properties.The selection of appropriate alloying elements plays a key role in the performance of magnesium alloys.It is found that the addition of Sn in some alloys can improve the mechanical properties and also obtain excellent damping properties.However,due to many factors affecting the performance of the alloy,its mechanism is still unclear.In this work,this paper selects Mg-Sn alloy as the research object,designs five groups of alloy compositions according to different Sn element contents,adjusts the alloy microstructure through heat treatment,hot extrusion,and hot rolling process,and systematically studies the Sn element on the damping and mechanical properties of magnesium alloys.To achieve the balance optimization of Mg-Sn alloy mechanics and damping properties,the performance influence law can provide a reference for the alloy design of low-cost,high-strength,and high-damping magnesium alloys.Firstly,the microstructure,mechanical,and damping properties of as-cast Mg-Sn alloy were studied.It is found that when the strain is 10-3,the damping value of the alloy with 7.3 wt.%Sn is 0.1514,which is higher than that of the alloys with 2.7 wt.%and 4.0 wt.%Sn.The main reason is the formation of a regular long-straight parallel second-phase structure.This special morphology is conducive to the formation of long-straight parallel dislocations,which can improve the damping performance of magnesium alloys.After solution heat treatment at 500°C,there is no special morphology in the alloy.At this time,the damping performance of the alloy containing 7.3 wt.%Sn is the lowest,and that of the alloy containing 4 wt.%Sn is the best.When the strain is 10-3,the damping value is 0.1878,which is related to a certain amount of Mg2Sn phase dispersed in the alloy.Then,the effects of Mg₂Sn on the microstructure and properties of the alloys were studied at extrusion temperatures of 250℃and 300℃,respectively.The results show that the unrecrystallized grains and the dispersed Mg₂Sn phase are beneficial to increase the dislocation line length per unit volume,thereby improving the damping performance of the alloy in the low-strain stage.In the high strain stage,the increase of Mg₂Sn phase content will reduce the damping performance of the alloy,but the effect of Mg₂Sn on the damping performance of the alloy can be weakened when the grain size is small.Among them,the alloy contains 1.4wt.%Sn at the extrusion temperature of 300℃has the best damping performance and better mechanical properties,the damping value is 0.0670(ε=10^-3),the tensile strength is 215MPa,and the yield strength 125 MPa,elongation13.2%.Finally,the effects of Mg₂Sn on the damping and mechanical properties of the as-rolled alloys under different pressing deformations were investigated.With the increase in the pressing amount,the content and distribution of the second phase did not change significantly,but the alloys were refined due to dynamic recrystallization.Among them,the damping properties of the alloys did not change much and the mechanical properties decreased when the depression deformation was low.When the depression amount increased to 50%,the strength and damping properties of the alloys were simultaneously improved,and the plasticity decreased to a certain extent.Therefore,in the rolled state,the full rolling deformation of the alloy is beneficial to improve the mechanical and damping properties.The improvement of damping properties is related to the increase of dislocation density,but when the content of the Mg₂Sn phase in the alloy is large,it is not conducive to the mechanical properties of the alloy.