| 6005A alloy is a heat-treatable Al-Mg-Si series aluminum alloy.Because of its high strength,good corrosion resistance and easy formability,it is commonly used in aviation,railway transportation,shipbuilding and automobile industries.Manufacturing of aluminum alloy parts.However,there is the absence of systematic research on the effect of quenching cooling rate on the performance of 6005 A alloy.The use of advanced heat treatment technology to effectively improve the performance of aluminum alloy and reduce production costs can make it more widely used.The dissertation performed heat treatment experiments with different quenching cooling rates(air cooling: 0.27 °C/s,Forced air cooling: 1.01 °C/s,water cooling: 47.27 °C/s)for6005A alloy,and obtained the Air-cooling natural aging state(AC),Forced air cooling natural aging state(FC-NA),Water-cooling natural aging state(WC-NA),Forced air cooling artificial aging state(FC-AA),Water-cooling artificial aging state(WC-AA)Five alloys in different states.At the same time,room temperature stretching,intergranular corrosion,stress corrosion and friction stir welding(FSW)was carried out on different alloys.The metallographic microscope,electron scanning microscope and transmission electron microscope were used to observe and analyze the microstructure of each sample,and the hardness test and tensile performance test were carried out using a micro hardness tester and a universal testing machine.The effects of quenching and cooling methods are commonly used in the industry on the mechanical properties.Corrosion resistance and friction stir welding properties of 6005 A alloy were explored in detail.The research results demonstrate that the greater the quenching cooling rate,the greater the hardness value of the alloy 6005 A.The artificial aging treatment at 160 °C can promote the precipitation of the strengthening phase ?'',which in turn helps to improve the strength and hardness of the alloy.The 6005 A alloy obtained with low cooling rate(Air-cooling)has the best plasticity and the worst yield strength and tensile strength.The 6005 A alloy obtained with a high cooling rate(Water-cooling)has the best yield strength and tensile strength and the worst plasticity.The strength and plasticity of the 6005 A alloy obtained a moderate cooling rate(Forced air-cooling)is between air cooling and water cooling quenching,and have excellent comprehensive mechanical properties.Distribution and density of ?' phase have a great influence on the ability of 6005 A alloy to resist intergranular corrosion and stress corrosion.The higher quenching cooling rate helps to improve the ability of 6005 A alloy to resist intergranular corrosion and stress corrosion.However,the fine and dense intergranular precipitation phase and the widespread precipitation-free precipitation band in the WC-AA sample have a significant galvanic effect,so they exhibit the worst resistance to intergranular corrosion.The AC sample has a large number of ?' phases inside and the grain boundary,and thus shows poor resistance to intergranular corrosion and the worst stress corrosion resistance.The state of the base metal does not significantly affect the grain size and structure of the weld nugget of the FSW joint,but the composition of the precipitated phase in the heat affected zone(HAZ)and the weld nugget(NZ)depends on the phase composition of the base metal(BM).The WC-AA samples with higher quenching rate show the maximum hardness in different areas of the FSW joint,this is because the high-density ?'' phase in BM,the high-density and small ?' phase in HAZ and the number of Many solute atoms and GP regions formed in NZ.In addition,fracture positions of FSW joints all occur in HAZ,the higher the hardness of HAZ,the higher the yield strength of the joint.WC-NA joints have a prominent structural uniformity during the stretching process,so they exhibit greater elongation and tensile strength than other FSW joints. |
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