铜钨/20钢双金属的液相扩散连接

Liquid phase diffusion bonding of CuW/20 steel bimetals

摘要:

本文首先研究了铜钨合金与20钢的直接扩散连接，发现整体材料在过渡层在铜钨近过渡层界面产生了脆性的Fe2W金属间化合物薄层，恶化了接头结合质量。为了解决此问题，引入Cu-2wt.%Cr夹层，在1200℃~1380℃的范围内制备了的铜钨/20钢整体材料。加入夹层后在铜钨与20钢界面形成了一个完整的冶金过渡层，消除了直接扩散连接过程中产生的Fe2W脆性金属间化合物薄层，在光镜下观察到界面过渡层由浅色的基体包围的深色蠕虫状组织构成，XRD与EDS能谱分析结果表明，其中的浅色基体为铜基体，黑色蠕虫状组织为富铁相。随着扩散连接温度的升高，界面过渡层中的深色蠕虫状组织由20钢一侧向铜基体中延伸，并不断长大。1250℃扩散连接时，深色蠕虫状组织均匀分布于整个过渡层。并对不同温度下的铜钨20钢复合材料进行了室温力学性能测试，发现1250℃时界面强度达到最大，为145Mpa。利用SEM对拉伸断口形貌观察，发现整体界面平整无韧窝，由Cu相韧性撕裂棱与平整的富铁相区域组成。

Abstract:

The liquid phase diffusion bonding between CuW alloy and 20 steel was studied. The brittle Fe2W intermetallic compound thin layer was formed at the interface of CuW near the transition layer of the monolithic material, which seriously deteriorated the mechanical properties of the joint. The CuW/20 steel monolithic material containing copper chromium interlayer was prepared in the range of 1200 ℃~1380 ℃. After the interlayer was added, a complete metallurgical transition layer was formed at the interface between CuW alloy and 20 steel, eliminating the thin layer of Fe2W brittle intermetallic compound produced in the process of direct diffusion bonding. It was observed under the optical microscope that the interface transition layer was composed of dark worm like structure surrounded by a light colored matrix. The results of XRD and EDS analysis showed that, The light colored matrix is divided into copper phase and the black vermicular structure is rich in iron phase. With the increase of diffusion bonding temperature, the dark worm like structure in the interface transition layer extends from one side of 20 steel to the copper matrix and grows continuously. When diffusion bonding at 1250 ℃, dark wormlike tissue is evenly distributed in the entire transition layer. The mechanical properties of CuW/20 steel composites at different temperatures were tested at room temperature. It was found that the interface strength reached the maximum of 145Mpa at 1250 ℃. The tensile fracture morphology was observed by SEM, and it was found that the overall interface was flat without dimples, consisting of Cu phase ductile tear edges and flat iron rich phase area.