控压摩擦焊大变形体系及其非连续性缺陷预测模型系统的热力学研究

Since the discontinuity defects are serious threat to the important structures and components welded by the friction welding carried out by controlling welding pressure, and considering the generally agreed opinion that “a special macro-state of the joint has its own corresponding microstructure”, this study aims to characterize the formation and evolution of the severe plastic deformation of the friction welding (SPD-FW), which is the essential process of the friction welding. Thus the following research is proposed: firstly, based on Onsager-Ziegler Maximum Entropy Production Principle, an analytical model in the thermodynamic framework is planned to build to describe ideal steady state of SPD-FW system. Secondly, according to the thermodynamic principle of the evolution of non-equilibrium system, the history dependence of the SPD-FW system will be analyzed to establish the thermodynamic analytical model of the whole process of friction welding, and then a comprehensive and accurate characterization of SPD-FW system will be obtained. Thirdly, based on this characterization, and referring to the idea and method used by constructing Ziegler’s instability criterion, the model predicting the discontinuity defects will be built to evaluate the stability of the plastic deformation of SPD-FW system. After this, the system in the stable regions (corresponding to the state spaces there are no discontinuity defects in theory) will be analyzed in order to discover and characterize the correlationship between the system’s entropy productions and its corresponding microstructures and mechanical properties. Finally, these characterizations and the discontinuity defects model will be integrated to build to a comprehensive model predicting discontinuity defects.

针对非连续性缺陷对旋转、线性等控压摩擦焊关键零部件的严重威胁，本研究从“接头体系宏观状态和历程与其微观结构相对应”这一基本思想出发，针对“大变形体系形成与演变”这一摩擦焊过程本质开展研究。首先，基于Onsager-Ziegler最大熵产生原理，构建以热力学为基本框架的理想定态大变形体系解析模型；其次，结合非平衡态体系演变热力学原则以及历史相关性分析，建立整个摩擦焊过程的热力学解析模型，获得实际大变形体系的准确表征；而后，基于此表征，针对大变形体系开放、非等温等特征，借鉴Ziegler失稳判据等塑变稳定性模型的构建思想与方法，以大变形体系的塑变稳定性为核心，建立非连续性缺陷预测模型；此后，在稳定区域内（即理论上不存在非连续性缺陷的状态空间），进一步，以熵产生为主要参量，分析组织、性能更为优异的体系特征，并建立相应的预测性表征；最终，将此表征与缺陷预测模型整合为完善的非连续性缺陷预测模型系统。

针对非连续性缺陷对旋转、线性等控压摩擦焊关键零部件的严重威胁，本研究从“接头体系宏观状态和历程与其微观结构相对应”这一基本思想出发，针对“大变形体系形成与演变”这一摩擦焊过程本质开展研究。以旋转摩擦焊为典型方法，构建了包括：C320摩擦焊机、扭矩采集系统、高速摄像机与红外热成像仪的测试系统。首先，抽象了以轴向缩短速率、大变形区宽度为典型响应参量，构建了其与试样材料、尺寸以及焊接参数等输入参量之间的解析模型；基于OZ-MEPP原理，构建了1D、2D、3D条件下，理想定态大变形体系熵产生率的解析模型。其次，将实际摩擦焊阶段性过程抽象为大变形体系孕育产生、扩展稳定、持续阶段，得到了全过程，摩擦阶段(孕育)、塑性变形阶段(扩展)、稳态阶段(持续)的熵产生率模型，建立了大变形体系形成与演变的热力学准则。而后，以熵产生为主要参量，建立了适用于大变形体系的塑性失稳判据，进而以熵产生和应变速率两状态参量为坐标，绘制了大变形的稳定与非稳定区，构建了非连续性缺陷预测模型。此后，在大变形稳定区，构建了基于熵产生的组织预测唯象模型，并根据Hall-Petch关系，建立了性能预测模型。基于焊接参数表征上述非连续性缺陷预测模型系统，最终以焊接参数为坐标，绘制了摩擦焊加工图。最后，采用摩擦焊常用的4类6种材料，铝合金AA1100、AA7075，钛合金TC4、TC17，不锈钢SUS304，高温合金GH4169等不同尺寸试件的共计60组有效的旋转摩擦焊实验，通过响应参量实测值与计算值的系统比较，对具有代表性的多个区域组织以及典型的54组接头力学性能进行表征，验证、优化实际摩擦焊过程OZ-MEPP热力学模型以及非连续性缺陷预测模型系统。研究结果将极大丰富摩擦焊工艺设计理论，对航空发动机、燃气轮机等盘－轴、叶—盘结构的摩擦焊设计与制造具有直接指导意义。