表面微加工对陶瓷/金属钎焊接头组织及应力分布的影响机理

This project introduces a new method which optimises the residual stress distribution in the ceramic/ metal joint via surface micromachining to fulfil the requirement of the new airspace engine, to achieve reliable brazing joints between SiBCN ceramic and the metals and to reduce the residual stress in the joint. A method to measure the residual stress distribution in the joint is developed as well. In this project, to measure and control the residual stress distribution in the joint, the micromachining pattern on ceramics is designed, and the effect of the micromachining process on the microstructure and the mechanical properties of the joint are investigated. The brazing parameters are optimised and the microstructure evolution of the joint is observed. The physical model of the joining process is set up. An image based model based on the observed microstructure of the joint is developed to predict the relationship between the residual stress distribution and the microstructure features. The residual stress distribution as a function of depth is measured and the effect of the micromachining process on the residual stress distribution is demonstrated. The joining mechanism is revealed. The aims of this project are to extend the application of micromachining in joining, to develop new methods to measure the residual stress distribution in brazing joint and to promote the development of ceramic/ metal joining theories and techniques.

本项目基于新型号航天发动机产品需求，针对SiBCN陶瓷与金属的高质量连接及接头应力控制难题，拟通过陶瓷表面微加工调控并优化接头内残余应力分布，提升陶瓷/金属连接质量，探索可行的残余应力分布无损测量方法。本项目以接头内残余应力的测量和调控为研究切入点，设计并优化陶瓷表面微加工图案，研究陶瓷表面微加工对接头组织及性能的影响，优化钎焊工艺参数并揭示接头组织的演化规律，建立界面反应模型，考虑界面反应产物特征建立接头的有限元模型，分析接头微观组织与微加工对残余应力分布的影响，实测验证接头内残余应力在深度方向上的分布，揭示陶瓷表面微加工对接头残余应力分布的影响机制，阐明接头的连接机理。本项目旨在推广表面微加工在连接领域的应用，突破陶瓷/金属接头应力无损测量的技术瓶颈，促进陶瓷/金属连接基础理论与应用技术的发展。

实现陶瓷与金属的可靠连接是突破新型号航天发动机研制瓶颈的关键，然而由于陶瓷与金属的线膨胀系数等物理性质不匹配，冷却过程中易在接头内产生较大的残余应力，降低接头的力学性能，甚至直接导致接头的开裂。本项目以残余应力的调控与测量为研究切入点，实现了SiBCN、AlON、Al2O3、石墨、YSZ等陶瓷与不锈钢以及TC4钛合金的连接，揭示了钎焊工艺参数对接头组织与力学性能的影响规律，提出了表面飞秒激光加工优化YSZ陶瓷/金属钎焊接头残余应力分布的新思路，开发了添加负膨胀系数增强相的复合钎料与纳米颗粒增强的网状中间层，缓解了多种陶瓷/金属钎焊接头的残余应力。基于拉曼光谱与X射线衍射技术开发了陶瓷/金属钎焊接头残余应力在深度方向上分布的测量方法，阐明了蓝宝石/TC4钛合金接头残余应力在深度方向上的分布特征，发现蓝宝石中的平面内应力为压应力，从表面到界面逐渐升高，离面应力在表面为拉应力随着深度的增加逐渐变为压应力，之后压应力值逐渐减小又变为拉应力，测量了使用不同含量增强相复合钎料获得的AlON/Ti2AlNb的残余应力，揭示了增强相含量对接头残余应力的影响机制，利用XRD技术阐明了中间层材料对石墨/铜接头残余应力分布的影响规律，揭示了接头的断裂机理，开发了陶瓷/金属接头残余应力原位测量装置，揭示了Al2O3陶瓷/不锈钢残余应力分布随温度的变化规律，发现了Al2O3陶瓷/不锈钢空气反应钎焊接头残余应力的非线性分布规律，观察了陶瓷/金属接头的二维与三维微观组织，并基于观察到的微观组织建立了有限元模型，阐明了表面飞秒激光加工对YSZ陶瓷/TC4钛合金接头残余应力分布的影响机理，揭示了Al2O3陶瓷/不锈钢空气反应钎焊接头组织特征对接头残余应力分布的影响机制，解明了接头残余应力非线性分布的机理。本项目为陶瓷金属接头残余应力环节提供了新思路，为陶瓷金属接头残余应力测量以及接头失效机理分析提供了参考。