铜钨/20钢双金属的液相扩散连接

Liquid Phase Diffusion Bonding of CuW/20 Steel Bimetals

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-2%Cr(质量分数)夹层,在1200~1380℃的范围内制备了铜钨/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基体包围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145 MPa。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。

The direct diffusion bonding of CuW alloy and 20 steel was investigated.Results show that the thin layer with brittle Fe2W intermetallic compound is produced at the interface of CuW/20 steel integral material near the CuW alloy side,which deteriorates the joint bonding quality.In order to solve this problem,Cu-2wt%Cr interlayer was introduced to into the CuW alloy/20 steel integral materials at the temperature of 1200~1380℃.After adding the interlayer,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 generated during liquid phase diffusion bonding.OM observation results show that the interface transition layers are composed of a dark vermicular structure surrounded by a light matrix.XRD and EDS analysis results show that the light colored matrix is copper matrix,and the black vermicular structure is iron-rich phase.With increasing the diffusion bonding temperature,the dark vermicular structure in the interface transition layer extends from one side of 20 steel to the copper matrix and continues to grow.When diffusion bonding occurs at 1250ºC,the dark vermicular tissue is evenly distributed throughout the transition layer.The mechanical properties of CuW alloy/20 steel bimetals prepared at different temperatures were tested at room temperature.It is found that the interfacial strength reaches maximum value 145 MPa at 1250ºC.SEM tensile fracture morphologies show that the overall interface is flat without dimples,and it consists of ductile tearing edges of copper phase and flat rich-iron phase areas.