SiC陶瓷与Ti合金的(Ag-Cu-Ti)-W复合钎焊接头组织结构研究

Research of Microstructure of Composite-brazing Joints of SiC Ceramics and Ti Alloy by Using (Ag-Cu-Ti)-W as Bonding Material

研究了在Ag,Cu,Ti粉末中加入W粉连接钛合金和SiC陶瓷的接头组织结构和接头状况。结果表明W颗粒均匀分布在钎缝的Ag相中,且未与Ag-Cu-Ti合金基体发生冶金反应,W颗粒的大小和形状基本上与加入前的粉末相当。在较低的钎焊温度和较短的钎焊时间下,能形成组织结构均匀、连接良好的复合接头,钎缝内Cu-Ti相较少,钎缝与钛合金界面形成了多层Ti含量呈梯度变化的Cu-Ti扩散反应层组成的扩散带。W的加入降低了接头热应力。而较高的钎焊温度和较长的钎焊时间,容易在近缝区的陶瓷中产生裂纹。由于扩散进入钎缝Ti量的增多,使得钎缝内形成很多长条形CuTi相组织,提高了与钎缝相邻的Cu-Ti扩散反应层的Ti浓度,并且钎缝内钛合金界面附近形成了没有W相的带状区域。

Situation and microstructure of the joints of SiC ceramics and Ti alloy brazed by the mixed powder of Ag, Cu, Ti and W were investigated. Experimental results demonstrate that W particles, remaining almost the same size and shape as primary W powder, evenly distribute in the Ag-phase of the bonding layer in the joint and do not react with Ag-Cu-Ti matrix. At suitable brazing temperature and holding time, a strong composite-joint possessing homogeneous microstructure can be acquired. In the joint, there are small amount of Cu-Ti phases in its bonding layer and the interfacial Cu-Ti multi-layers with Ti contents in gradient change through reactive diffusion between Ti-alloy and the bonding layer; the existence of W particles debases the thermal stress of the joint. Whereas, with further increasing the brazing temperature and the time, flaws will appear in the SiC ceramics near bonding layer; meanwhile, a great deal of Ti diffuse into the bonding layer, causing the elevation of the Ti content of the Cu-Ti interracial layer neighboring the bonding layer and the formation of many strips of CuTi phase in the bonding layer and the generation of the zone without W in the bonding layer adjacent to the interfacial layers.