6009铝合金激光电弧复合焊接头腐蚀性能研究

Study on Corrosion Properties of 6009 Aluminum Alloy Joint by Laser-arc Hybrid Welding

通过金相观察、电化学腐蚀试验、晶间腐蚀试验和静态腐蚀失重试验,发现当热源间距为2mm时,接头在3.5%NaCl溶液中的电化学腐蚀特性优于3mm和4mm时的接头。同时,该条件下焊接接头晶间腐蚀敏感性低于其它热源间距的接头。但热源间距对接头的均匀腐蚀速率影响很小。经过固溶淬火加时效处理的焊接接头耐电化学腐蚀性优于焊态接头,晶间腐蚀敏感性低于后者。另外,此热处理方法有助于减缓接头区均匀腐蚀速率。进一步分析表明,热源间距为2mm时的接头中,柱状晶在生长过程中,树枝晶得不到充分的发展,分枝较少,结晶后显微疏松等晶间杂质少,组织比较致密。固溶淬火加人工时效消除了焊缝的氢气孔,减少了侵蚀性阴离子对基体的吸附作用;同时,大量Mg、Si原子重新溶入铝合金基体,晶界杂质原子较焊态减少。

Electrochemical corrosion properties of joint when the distance between heat source is 2mm in 3.5%NaCl solution is superior to that of 3mm and 4mm by optical microscopy,electrochemical corrosion test,intergranular corrosion test weight loss and static corrosion test.At the same time,sensitivity to intergranular corrosion of joint under this condition is less than that of other distance between heat source.But the distance between heat source has little effect on the uniform corrosion rate of joint.Electrochemical corrosion resistance of joint by solution quenching and aging treatment is superior to that of as-welded joint and has less intergranular corrosion sensitivity than the latter.Additionally,this heat treatment method helps slow the uniform corrosion rate of joint area.Further analysis showed that in the joint under the distance of 2mm between heat source,crystal is not fully the development of the branch.in the process of growth of the columnar crystal,branch less,so that microporosity and intergranular impurities after the crystallization is few,microstructures is more dense.Solid solution hardening and artificial aging eliminates the weld porosity of hydrogen,reduce the aggressive anion adsorption of matrix;At the same time,a large number of Mg and Si atoms was dissolved back into aluminium alloy matrix,impurity atoms on the grain boundary are less than that of as-welded state.