湿度对铝合金接头裂纹敏感性的影响规律及机理

采用能谱、扫描电镜和X射线衍射等测试方法，研究了湿度对铝合金接头裂纹敏感性的影响规律及机理. 结果表明，在40% ~ 80%相对湿度的条件下，改良的铝合金鱼骨试件接头表面可见结晶裂纹和液化裂纹；随着湿度的增大，接头裂纹敏感性逐渐提高，其中结晶裂纹的敏感性逐渐降低，液化裂纹的敏感性逐渐提高；湿度增大，铝合金焊缝晶粒逐渐细化，裂纹扩展阻力升高，焊缝组织细化导致结晶裂纹敏感性降低；同时提高湿度，电弧温度降低，焊接热输入量减少，液态金属越发不易在晶界处形成连续的网状薄膜结构，也导致结晶裂纹敏感性降低.

Effect of humidity on crack sensitivity of aluminum alloy weld joint and its mechanism

Effect of humidity on crack sensitivity of aluminum alloy weld joint and its mechanism were studied by EDS, SEM and XRD. Results showed that under the 40 % ~ 80% relative humidity conditions, solidfication cracks and liquation cracks on the surface of modified herringbone specimens were observed. With the increase of humidity, the crack sensitivity of the joint increased gradually, in which the sensitivity of the solidfication crack decreased, and the sensitivity of liquation crack increased gradually; As humidity increasing, the grain size of the aluminum alloy weld seam was gradually refined, the crack propagation resistance increased, which led to the reduction of the sensitivity of the solidfication crack. At the same time, as humidity increasing, the arc temperature decreased, and the welding input decreased. It was difficult for liquid metal to form continuous network film structures at grain boundaries, which also reduced the sensitivity of solidfication crack.