铝合金 TIG 焊接接头喷射式微弧氧化腐蚀疲劳性能研究

目的研究铝合金TIG焊接接头经喷射式微弧氧化后对腐蚀条件下疲劳寿命的影响,为延长焊接接头的使用寿命提供一种有效的方法。方法采用TIG焊对5083铝合金进行焊接,观察焊接接头的组织结构,测试焊接接头的显微硬度距焊缝中心的分布情况;通过喷射式微弧氧化方法处理焊接接头,考察陶瓷层的生长曲线和截面纳米硬度;在最大载荷量为7,8,9 k N的条件下,分别对微弧氧化处理与未处理的焊接试样预腐蚀168 h后进行等幅拉伸疲劳实验,对比两种试样拉断时的循环次数。结果铝合金焊接接头呈现不均匀性,微弧氧化后接头陶瓷层均一性较好;陶瓷层厚度增长呈现先快后慢的趋势,表面粗糙度与厚度相关,呈近似线性增长;7,8,9 k N的载荷下,未处理的焊接接头相比于喷射式微弧氧化的接头,疲劳寿命分别降低50.7%,58.3%,64.9%。结论采用喷射式微弧氧化处理可改善铝合金TIG焊接接头的表面状态,阻隔外界腐蚀介质对焊接基体的侵蚀,提高其在预腐蚀和交变应力条件下的疲劳寿命,延长结构零件的使用寿命。

Corrosion Fatigue Properties of Aluminum Alloy TIG Welded Joint Treated by Spraying Micro-arc Oxidation

Objective To study the effect of spraying micro-arc oxidation on the corrosion fatigue life of aluminum alloy TIG welded joints, in order to provide an effective method for prolonging the life of welded joints. Methods The 5083 aluminum alloy was welded using TIG welding, the microstructure of the welded joint was observed, and the micro-hardness distribution of welded joints with the distance from the weld center was tested. The growth curve and cross-section nano-hardness of the ceramic coating were investigated after spraying MAO treatment. Under the three loading conditions with the max-stress of 7 kN,8 kN,9 kN, the tensile fatigue test was conducted for welded samples treated by micro arc-oxidation and the untreated samples after 168 h of pre-corrosion, and the fatigue life of the two samples was compared. Results The surface state of welded joints of aluminum alloy was not uniform, whereas the ceramic coating of joint showed good uniformity after micro-arc oxidation. The increment in thickness of the ceramic layer was first fast and then slow, and the surface roughness showed a nearly linear positive correlation with the thickness. Under the three loading conditions (7,8,9 kN), the fatigue life of the untreated welded joints decreased by 50. 7% ,58. 3% ,64. 9% respectively, compared with those after spraying micro-arc oxidation treatment. Conclusion The surface condition of TIG welded joints could be improved by spraying micro-arc oxidation, which blocked the erosion of weld substrate by corrosive medium, and improved the fatigue life of aluminum alloy and equipment parts under corrosion and alternating stress.