Study On Mechanical Properties,Damping Capacity And Thermal Conductivity Of Mg-Zn-Ga Alloy

Magnesium(Mg)alloys have great application potential in the fields of electric and electronic,precision instruments and shell of high-power electrical appliances because of their excellent properties such as low density,high specific strength,good electromagnetic shielding performance and excellent damping capacity.Besides,the applications in these fields require Mg alloys to have good plasticity as well as to exhibit high thermal conductivity to increase the service life of the component.The development of high damping magnesium alloys with good plasticity and thermal conductivity has high academic value and practical application valueIn view of the strong strengthening effect and the small influence on thermal conductivity of Zn in magnesium alloy,the significantly improved plasticity by Ga addition and good damping capacities involved with both Mg-Zn and Mg-Ga alloys,the thesis has proposed to develop high damping magnesium alloys with good plasticity and high thermal conductivity on the basis of the Mg-Zn-Ga alloy system.Effects of the Zn/Ga ratio on mechanical properties,damping capacity and thermal conductivity of Mg-xZn-yGa(x+y=1at.%)alloys in different states including as-cast,solid solution and high strain rate rolling(HSRR)are systematically investigated.The relations of mechanical properties,damping capacity and thermal conductivity with solute atomic characteristics,grain size,the feature of second phase and texture of these alloys are clarified.The potential of achieving good plasticity,excellent damping capacity and high thermal conductivity of fine-grain Mg-Zn-Ga alloy sheet by HSRR is explored,and the related mechanism is revealed.The main research results of the paper are as follows:(1)The effect of Zn/Ga ratio on mechanical and damping properties of Mg-Zn-Ga alloy was clarified.The results show that the yield strength and elongation of the assolutionized Mg-Zn-Ga alloy increase with the decrease of the Zn/Ga ratio.Its strainamplitude-independent damping capacity decreases,while its strain-amplitudedependent damping capacity increases and the growth rate increases with the increase of the Ga content.n the average grain size range of 81-452 μm,the strain amplitudedependent damping value of as-solutionize Mg-1Ga alloy decreases first and then increases as the grain size increases.(2)The effect of Zn/Ga ratio on mechanical and damping properties of Mg-Zn-Ga alloy sheet rolled at high strain rate was investigated.The results show that with the decrease of the Zn/Ga ratio,the tensile strength of rolled Mg-Zn-Ga alloy sheet decreases first and then increases,while the elongation increases slightly.The damping value decreases with the decrease of Zn/Ga ratio at lower strain amplitude,and the growth rate of damping value increases with the decrease of Zn GA ratio at high strain amplitude.(3)The thermal conductivity characteristics of as-cast state,as-solutionized and as-HSRRed Mg-Zn-Ga alloys are revealed,and it is found that stacking fault e nergy and electro-negativity are the key factors affecting their thermal conductivity.The asHSRRed Mg-Zn-Ga alloy sheet has excellent thermal conductivity at room temperature,and its thermal conductivity decreases with the decrease of Zn/Ga ratio.The effect of grain size on the room temperature thermal conductivity of Mg-Zn-Ga alloy is small.Mg-0.75Zn-0.25 Ga alloy sheet has the best comprehensive mechanical,damping and thermal conductivity properties,with the yield strength,tensile strength and elongation of 196 MPa,263 MPa and 30%,respectively;when the strain amplitude is 0.1%,the damping value is 0.016;its thermal conductivity at room temperature is 131.2 W/(m·K).