铝/钢异种金属火焰钎焊接头组织和性能

Microstructure and mechanical properties of aluminum/stainless steel brazed joint with torch brazing

关键词:  火焰钎焊  铝合金  不锈钢  显微组织  抗剪强度

Key words:  torch brazing  aluminum  stainless steel  microstructure  shear strength

摘要:

通过扫描电镜、能谱分析和X射线衍射等方法研究了火焰钎焊时Zn-xAl钎料的润湿性能、铝/钢钎焊接头界面显微组织、金属间化合物层以及接头抗剪强度.结果表明,Zn-xAl钎料配合改性CsF-RbF-AlF₃钎剂,可以有效地去除母材表面氧化膜,从而提高钎焊接头力学性能.随着Al元素含量增加,钎料铺展性和填缝性随之提高,但是钎焊接头强度先升后降,Al元素含量为15%时,钎焊接头力学性能最佳.钎焊接头显微组织分析结果表明,金属间化合物主要为Fe₄Al₁₃相. Zn-xAl钎料中Al元素含量较低时,界面层由富锌相和Fe₄Al₁₃相组成.随着Al元素含量的增加,在Zn-25Al钎焊接头界面出现第二层金属间化合物Fe₂Al₅相.

Abstract:

The wettability, microstructure, intermetallic compound (IMC) layer and mechanical properties of aluminum/stainless steel joints brazed with Zn-xAl filler metals were investigated by means of scanning electron microscope, energy dispersive X-ray spectrometer and X-ray diffraction. The results indicate that the oxide film on the base metal could be effectively removed by the modified CsF-RbF-AlF₃ flux, and the excellent mechanical properties of the brazed joints were obtained. The spreading area as well as the clearance filling ability of Zn-xAl filler metal was both improved with by increasing the content of Al in the filler metals. However, the shear strength of the joint increased first and decreased afterwards, and the best mechanical property of brazed joint is obtained when the content of Al is 15%. It has been found that when the content of Al is low, the interfacial layer is composed of Zn-rich and Fe₄Al₁₃ phase. As for the excessive amount of Al, additional Fe₂Al₅ phase is visible at the interface.