| High aluminum zinc alloy is widely used because of its excellent mechanical properties,friction characteristics and manufacturability,as well as its advantages of low specific gravity,low energy consumption and no pollution.However,the existing ZX09 zinc alloy in Zhuzhou Smelting Group has poor creep resistance and high production cost due to high copper content.Therefore,alloying is adopted to improve the creep resistance of zinc alloy and reduce the copper content.In this paper,based on compositions and properties of ZX09 zinc alloy of Zhuzhou smelting group,ZA12 zinc alloy was alloyed with Si and Si+Ti.On the basis of determining the optimum Si and Ti content,the Cu content was optimized,a low-copper high-aluminum zinc alloy with lower cost was obtained at last.The microstructure and mechanical properties of the zinc alloy were studied by means of optical microscope,scanning electron microscope/energy dispersive spectrometer,micro Vickers hardness tester,pendulum impact tester and electronic universal tensile tester.The research results have important guidance and application value for the development and industry production of zinc alloy.The experimental results show that when 0.1 wt.%Si and 0.8wt.%Si are added to ZA12 zinc alloy in the form of Al-20Si and Al-12.6Si master alloy respectively,fine silicon phase could be formed in zinc aluminum alloy.Silicon addition increases the hardness of the zinc alloy,but obviously reduces the impact toughness of the alloy.After adding 0.8 wt.%Si+0.3wt.%Ti into ZA12 alloy,the hardness and impact toughness are137.8 HV and 23.8 J/cm2,respectively,which are 12.7%and 28%higher than those of non-alloyed ZA12 zinc alloy.The improvement of the comprehensive mechanical properties of ZA12 which is complex alloyed by Si and Ti elements is attributed to the complex strengthening effect of fine Ti Si2 particles and relatively small silicon particles in the alloy.With the increase of copper content,the hardness of zinc alloy containing silicon and titanium gradually increases and the impact toughness first increases and then decreases.When 2.0wt.%Cu is added,the comprehensive mechanical properties of the zinc alloy are the best.Because of the lower Cu content in the alloy,the cost of the newly developed zinc alloy is obviously lower than that of ZX09 alloy prepared by Zhuzhou Smelting Group Co.,Ltd.The?+?eutectoid structure in microstructure of low copper and high aluminum zinc alloy prepared with melting temperature of 600?and metal mold temperature of 100?is in the form of short rod,and the Ti Si2 phase is in moderate size and evenly distributed in the matrix.At this time,the microstructure and comprehensive mechanical properties of the low copper and high aluminum zinc alloy are at the best state.The tensile fracture morphology of low copper and high aluminum zinc alloy prepared possesses many small dimples and many tiny tear edges as well as a few cleavage surface with small size,which reveals that the alloy has high tensile strength and elongation as well as impact toughness.The results show that when low copper and high aluminum zinc alloy is subjected to tensile creep under the stress range of 100?140MPa at the temperature range of 80?120?,the constitutive equation of tensile creep of the alloy is??s=1.43×10-6?4.58exp(-64060/RT).The average stress index of the alloy is 4.58 and its average apparent creep activation energy is 64.06 KJ/mol.The tensile strength and elongation of the zinc alloy with low copper and high aluminum are 355.5Mpa and 2.4%,respectively.The tensile strength is 41%higher than that of ZX09 zinc alloy and 86.3%higher than that of ZX10 zinc alloy.The elongation is3.3 times that of ZX09 zinc alloy and 7 times that of ZX10 zinc alloy.Although its creep displacement and steady creep rate are higher than those of ZX09 and ZX10 zinc alloys,the creep life of low copper and high aluminum zinc alloy is larger than that of ZX09 zinc alloy,but smaller than that of ZX10 zinc alloy. |
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