织构化表面对异质金属润湿性及界面反应的影响

Effect of textured surface on wettability and interfacial reaction of heterogeneous metals

不锈钢与铝合金广泛应用于火箭贮箱中隧道管与补偿器的焊接,熔钎焊已成为其主要连接方式,但接头存在低应力开裂,容易引起燃料泄漏等问题。为提高接头可靠性,首先采用超快激光加工技术在不锈钢表面烧蚀制备了微槽和微坑两种典型的织构化表面。然后,通过铝合金在不锈钢表面的原位润湿铺展试验研究了两种微织构对润湿铺展方向、接触角和界面反应产物的影响。试验结果表明铝合金具有沿微槽加工方向润湿铺展的趋势,而微坑的铺展则接近圆形;在微槽表面表现出更小的接触角,同时基于Wenzel方程对在两种表面润湿铺展的接触角进行数值计算,计算结果略大于实际结果。最后,分析了界面冶金反应对润湿铺展的影响。结果表明界面反应对铝合金的润湿铺展具有一定的促进作用,但过于粗大的界面反应产物则会阻碍润湿铺展。该激光织构化的方法不仅可用于不锈钢与铝合金体系,还可用于航空航天领域中其他金属与金属、金属与非金属之间的连接。

Stainless steel and aluminum alloy are widely used in welding of tunnel tubes and compensators in rocket storage tanks.Fusion brazing has become the main connection method,but the joints obtained by fusion brazing suffers from low stress cracks,which can easily cause fuel leakage and other problems.To improve the reliability of the joint,this study used ultrafast laser processing to ablate the surface of stainless steel,and prepared two typical textured surfaces:micro-groove and micro-pit surfaces.Through the in-situ wetting test of aluminum alloy on the surface of stainless steel,the influence of two micro-textures on the wetting and spreading direction,contact angle and interface reaction products was studied.The results show that the aluminum alloy exhibits a tendency of wetting and spreading along the processing direction of the micro-grooves,while the spreading of the micro-pits is close to a circle.On the micro-grooves’surface shows a smaller contact angle.Based on the Wenzel equation,the contact angles on the two micro-textured surfaces are calculated numerically,and the calculated results are slightly larger than the actual results.Finally,the influence of the interfacial metallurgical reaction on the wetting and spreading of the material’s surface is analyzed.The results show that the interfacial reaction can accelerate the wetting and spreading processes and promote the wettability to a certain extent,but excessively coarse interface reaction products will hinder the wetting and spreading process.The laser texturing method can be used not only for stainless steel and aluminum alloy systems,but also for connections between other metals,and between metals and non-metals in the aerospace field.