塑性变形对2024铝合金拼焊接头腐蚀性能的影响

Influence of plastic deformation on corrosion performance for 2024 aluminum alloy tailored welded joint

为研究变形程度对铝合金搅拌摩擦焊(FSW)接头腐蚀性能的影响规律。采用单向拉伸试验,通过Tafel极化曲线及剥落腐蚀试验研究不同程度的塑性变形量对2024铝合金FSW接头焊核腐蚀性能的影响,利用金相显微镜(OM)、扫描电镜(SEM/EDS)等观察得到的显微组织来表征试验结果并分析其影响腐蚀性能的机理。结果表明:在变形量为0%、4%、7%和10%的塑性变形中,耐腐蚀性依次为:变形量为0%的试样>变形量为7%的试样>变形量为10%的试样>变形量为4%的试样,在塑性变形量为7%处出现“拐点”。随着塑性变形量的增大,位错及位错环增多,包围缠绕的析出相增多,耐腐蚀性随之提高;但大的变形会使塑性变形量为10%的试样上出现微裂纹,容易被腐蚀,导致耐腐蚀性有所下降。

In order to study the influence laws of deformation degree on the corrosion performance of friction stir welding(FSW)joint for aluminum alloy,using uniaxial tensile tests,the influences of plastic deformation amount in different degrees on the corrosion performance of 2024 aluminum alloy FSW joint were studied by Tafel polarization curve and exfoliation corrosion test,and the test results were characterized by the microstructures observed by optical microscope(OM)and scanning electron microscope(SEM/EDS)to analyze the mechanism of its influence on the corrosion performance.The results show that in the plastic deformation amount of 0%,4%,7%and 10%,the corrosion resistance performance of FSW joint is as follows:the sample with deformation of amount 0%>the sample with deformation of amount 7%>the sample with deformation amount of 10%>the sample with deformation amount of 4%.An“inflection point”appears at the plastic deformation amount of 7%.With the increasing of plastic deformation amount,the number of dislocations and dislocation rings increases,the number of precipitation phases surrounding and winding increases,and the corrosion resistance performance also increases.However,large deformation causes micro-cracks on the sample with plastic deformation amount of 10%,which is easy to be corroded,resulting in a decrease in the corrosion resistance performance.