Static tensile crack behavior of brazed joints of dissimilar metals tubes in aerospace system
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摘要: 采用高频感应钎焊方法连接了航天推进系统的异种金属(钛合金与不锈钢)薄壁小直径导管结构,结构的质量和性能远远优于螺栓连接的导管结构.钎焊接头静态拉伸试验发现,银基钎料钎焊的接头承载能力要优于铜基钎料.对静态拉伸断裂接头的微观组织进行了分析,结果发现,银基钎料钎焊的接头区域出现的裂纹仅在钎缝区域萌生和扩展,当裂纹扩展到钎缝与母材的界面位置时停止扩展.铜基钎料钎焊的接头区域的裂纹从3个位置萌生:钎缝2种组织的交界处,钎缝与钛合金、不锈钢的界面.裂纹驱动力主要是由静态拉伸载荷和异种金属钎焊接头失配行为构成的,而裂纹扩展抗力主要与钎焊接头的微观组织有关.Abstract: The dissimilar metals(such as Titanium alloy and stainless steel) thin-wall small-diameter tube structrues in aerospace propulsion system were bonded, using high frequency induction brazing process. Their qualities and properties are largely superior to the bolt connection tubes structures. The static tensile experiments of the brazed joints were conducted. The results indicate that the mechanical properties of joints brazed using Ag-based filler metals are slightly better than those using Cu-based filler metals. And then the joints microstructures after static tensile experiments were analyzed. It is found that, all the cracks in the joint area brazed by Ag-based filler metals germinate and propagate in the brazing seam, the cracks stop when they propagate on the interfaces between brazing seam and the base metals. The cracks in the joint area brazed by Cu-based filler metals germinate in three locations: the boundary of two phases in the brazing seam, the interface between brazing seam and Titanium alloy, the interface between brazing seam and stainless steel. The crack driving force consistes mainly of the static tensile load and the mismatch behaviour of dissimilar metals brazed joint. And the resistance force of crack extension is related to the microstructures in the brazed joint.
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