| With the development of automobile lightweight,the thickness of automobile radiator fins gradually decreases from 0.2 mm to 0.08 mm.After thinning,the mechanical properties and brazing properties of 3003 aluminium alloy sheet used for automobile radiator fins are not satisfactory.At present,the research at home and abroad through adding zinc to 3003 aluminum alloy to meet the requirements of radiator performance.However,with the addition of Zn,the crystallization range of 3003 alloy is increased and the rolling force is increased,which limits the production of casting and rolling.High-throughput continuous casting and rolling(HTCR)with short process and low cost has great advantages in the production of 3003+Zn aluminum alloy sheets,but no relevant research reports have been reported at home and abroad.The microstructures,mechanical properties,brazing properties and corrosion resistance of 3003+Zn(1.4%)aluminium alloy produced by High-throughput continuous casting and rolling(HTCR)were studied by means of optical microscopy,SEM,DSC,mechanical properties,electrochemical analysis and salt spray corrosion.The main results are as follows:The formation process of Zn in the second phase of 3003+Zn aluminum alloy is through free substitution between Fe and Zn at high temperature.The addition of Zn did not change the morphology and distribution of the second phase.The solid solution of Zn in the matrix and the second phase had obvious strengthening effect.1.4% Zn increased the strength of the alloy by 22.4 Mpa.The high temperature deformation resistance of 3003+Zn alloy is higher than that of 3003 alloy.After high temperature treatment,the size and quantity of the second phase in the alloy decrease significantly.The second phase hardening effect is weakened,but the solid solution strengthening effect of zinc in the matrix still exists,which makes the high temperature deformation resistance of 3003 + zinc alloy better than that of 3003 alloy.The Zn element in 3003+Zn alloy can not only effectively avoid the corrosion during brazing,but also cause the oxide film on the metal surface to be removed by chemical reaction.The spreadability of the alloy sheet was obviously improved by Zn element,and the spreading area was increased by 22.3%.The zinc element in 3003+Zn alloy reduces the wetting angle between base metal and filler metal,and reduces the critical nucleation radius of new phase,which makes nucleation easier.The structure of the brazed joint of 3003+Zn alloy is mainly zinc-based solid solution and eutectoid tissue,while that of 3003 alloy is mainly aluminum-based solid solution and hypoeutectoid tissue.The hardness of the brazed joint of 3003+Zn alloy is lower than that of 3003 alloy.It avoids brittleness of brazed joints caused by high hardness.The electrochemical experiments show that the corrosion current density of 3003+Zn alloy is 1.6 times that of 3003 alloy,and the self-corrosion potential of 3003+Zn alloy is close to that of 3003 alloy.The corrosion resistance of the alloy decreases mainly by increasing the corrosion current density of the alloy.On the other hand,the addition of Zn significantly improves the breaking potential of the alloy and makes the passivation effect more obvious.Generally speaking,in neutral medium,the corrosion resistance of 3003+Zn alloy is close to that of 3003 aluminium alloy,which belongs to the first level of corrosion resistance.Weightlessness test shows that the corrosion of aluminum alloy in different corrosion media shows different corrosion rules.Aluminum alloy is always in corrosion zone in acidic medium.The corrosion resistance of 3003 + Zn alloy in acid is weaker than that of 3003 alloy. |
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