扩散连接Ti2AlNb/GH4169反应动力学研究

Study on Reaction Kinetics in Diffusion Bonding of Ti2AlNb and GH4169 with Nb+Ni Foils as Interlayer

摘要:

研究了Ni+Nb为中间层对Ti2AlNb与GH4169真空扩散连接反应动力学过程。结果发现：主要影响接头剪切强度的Ni6Nb7层厚度存在一个最佳值，通过最小二乘法拟合得最佳厚度为3.36 μm。根据修正的有效生成热理论和有效吉布斯自由能理论均预测Ni6Nb7为Ni-Nb固-固界面反应的初生相，因此在连接过程中Ni6Nb7相的出现是不可避免的。由于Ni6Nb7的生长速度低于Ni3Nb，因此可以通过优化工艺参数来控制Ni6Nb7层的厚度来提高接头的力学性能。通过Ni6Nb7层最佳厚度和生长速率计算可得知最佳保温时间约为49.5 min，实验结果表明，连接温度1050 ℃，压力20 MPa，保温时间为49.5 min时，Ni6Nb7厚度为3.37 μm，接头剪切强度达到468.2 MPa。

Abstract:

The process of reaction kinetics was investigated for vacuum diffusion bonding of Ti2AlNb and GH4169 by inserting metal foils of Ni+Nb as interlayer. The results show that there is an optimum thickness (about 3.36 μm) for the reaction layer Ni6Nb7, which is the main factor that influences the joint’s shear strength. The modified effective heat of formation (MEHF) theory and the effective Gibbs free energy theory were applied to predict that Ni6Nb7 is the primary phase formed during Ni-Nb interface reaction, i.e., Ni6Nb7 phase inevitably forms during the bonding process. The growth rate of Ni6Nb7 layer is lower than that of Ni3Nb layer. Thus it is possible to control the thickness of Ni6Nb7 layer by optimizing the processing parameters so as to improve the mechanical properties of the joints. The optimized duration time for the samples bonded at 1050 oC under 20 MPa is 49.5 min. This condition issues experimental shear strength of the joint as 468.2 MPa.