| Zinc-aluminum alloy(referred to as Zn-Al alloy)is an environment-friendly alloy,with the difference of Al content,alloys may have a lower hardness,high elongation,room temperature superplasticity,no work hardening behaviours,good wear resistance and high damping shock resistance characteristics.Through a proper solid solution heat treatment and plastic deformation processing,Zn-Al alloy can be obtained at room temperature with ultra-fine crystal or even nanocrystalline.Zn-A1 alloys are expected to replace the widely used mild steel dampers and toxic lead dampers in the construction engineering as high damping materials.In this thesis,based on the literature research and preliminary research of the laboratory,the microstructures and mechanical properties(including damping performance)of Zn-Al eutectoid alloys Zn-22A1(wt.%,the same unit in the following)and other Zn-xAl alloys with different aluminum contents were studied.A series of Zn-xAl alloys with different aluminum contents were prepared by different heat treatment and heat mechanical rocessing.The relationship between the microstructure,mechanical properties and damping performance of Zn-Al alloy was studied by investigating the microstructure,hardness,elongation,tensile strength and thermomechanical analysis(DMA)of the alloys.The main work and results are:In the first section,the microstructure of the Zn-22A1 eutectoid alloy,reported in several available literatures was adjusted by adding additional modifier.After adding small amount of modifier Ti and the rare earth(RE)element with metalloy state,the alloy exhibits fine equiaxed grains with a grain size of about 12?m.The reason is that at the high temperature stage during smelting and casting procedure,resulting in a high melting point of the metal compound TiA13,which is a strong metamorphic refinement for Zn-Al alloy as the crystal nuclei,the grains are refined without affecting the mobility of the interface,can improve the microstructure.The mechanical properties of the refined Zn-22A1 alloy by different heat treatment methods were obtained,which revealed that the best mechanical properties of the alloys is obtained by heat treatment with 360?/24 h/WQ(water quenching)and then following by hot rolling after re-heating with 360?/1h,finally the sample is cooled in the air.In this process condition,the minimum hardness of the alloy can reach 45.5HV,the maximum elongation up to 165%,tensile strength with 284MPa,and damping loss factor tg? with 0.05398,which is 1.3 times higher than that of the cast alloy.However,the alloy has the best damping performance under the heat treatment with 360?/24h/WQ.In this heat treatment process,the maximum value of the damping loss factor tg? of the alloy reaches 0.06182,which is 1.7 times higher than that of the as-cast Zn-22Al-0.1Ti-0.2RE(wt.%).The microstructure and mechanical properties of Zn-xAl alloys with different aluminum contents under different thermomechanical treatment processes were analyzed.The results show that the alloy consists of both ? and ? phases after subjected to different heat treatment and plastic deform process.The five kinds of Zn-A1 alloys have the best damping performance under the heat treatment proces with 360?/24h/WQ+150?/48h/WQ.Among these five Zn-Al alloys,the best damping performance still belongs to Zn-22A1 alloy.In this heat treatment process for Zn-22A1 alloy,the minimum hardness value reaches 42.83HV,elongation is up to 159%,tensile strength with 303MPa,damping loss factor tgS with 0.04661,which show considerable superplasticity.At the same time,the damping performance of the Zn-xAl alloy increases with the increase of temperature at all vibration frequency.And the damping performance of the alloy is reduced with the increase of vibration frequency. |
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