三元混杂增强耐热钛基复合材料的形变损伤及断裂行为

The fracture behavior of metal matrix composite is the most common failure mode and important factor which influences the hot workability of materials. It is always the focus point for scientists to study the damage and fracture behavior of ceramic particles reinforced metal matrix composites. In this project, the plastic forming and damage failure theory will be combined together, and TiB+TiC+La2O3 tri-reinforced high temperature titanium matrix composites were chosen as the investigated subject., the fracture characteristic of titanium matrix composite could be investigated by SEM and TEM dynamic tensile test. And a high speed photography method will be firstly used to study the high temperature fracture process and crack propagation rate. Meanwhile, the fracture characteristics of the reinforcements and the fracture mechanism at room temperature/high temperature could be revealed by combing with the different heat treatment. From the explanation of the effect of fracture mode on the failure behavior, a controllable microstructure defect method was developed for hybrid reinforced titanium matrix composite. This project will provide a solution to obtain a high integration between strength and plasticity for high temperature titanium matrix composite. It also will offer a good theoretical guidance to the damage and fracture behavior of other metal matrix composites.

金属基复合材料的断裂是塑性加工过程中最常见的失效形式，也是影响此类材料热加工性能的重要因素之一。本项目拟结合金属材料塑性加工理论和损伤失效理论，以TiB+TiC+La2O3三元混杂增强耐热钛基复合材料为研究对象，基于SEM和TEM原位观察实验测试材料在低/高应变速率下的室温失效断裂特征，采用高速摄影测量复合材料高温变形断裂过程和扩展速度，并结合不同热处理工艺揭示复合材料的室温和高温断裂机制以及增强体的断裂特征，阐明多元多尺度增强体断裂方式对材料失效的影响机制，建立多尺度钛基复合材料损伤—断裂演化多参数模型，实现难变形三元混杂增强耐热钛基复合材料组织缺陷的控制，为进一步提高耐热钛基复合材料强韧性提供新的思路，并对其它非连续增强金属基复合材料多尺度增强体损伤断裂行为的研究具有很好的借鉴和理论指导意义。

研制和开发具有良好综合性能的耐高温钛基复合材料对满足航空航天等国家重大需求具有重要的科学意义和使用价值。然而，增强体的存在，使得耐高温钛基复合材料的制备和热加工非常困难，材料在承载时内部的微损伤会发生串联和汇合引起材料内部裂纹萌生和扩展，最终导致开裂。因此，本研究以三元混杂和二元混杂增强钛基复合材料为研究对象，结合塑性加工理论和损伤失效理论，研究了三元颗粒增强钛基复合材料损伤-断裂演化规律，实现了难变形三元颗粒混杂增强钛基复合材料组织缺陷的有效控制。研究结果发现，三元混杂增强钛基复合材料损伤失效主要表现为典型的脆性断裂特征，其原因主要源于TiB和TiC增强体中存在的大量缺陷。多元颗粒增强钛基复合材料的断裂行为主要表现为，受载过程中增强体的断裂易于萌生微裂纹在界面处，基体同时出现滑移带，微裂纹和滑移带的相互耦合、贯通并导致最终材料的断裂失效。在塑性变形阶段，高含量增强体的断裂会使微裂纹增多，进而扩展后易于与邻近微裂纹或滑移带相互贯通，从而扩展成为宏观裂纹，降低材料的塑性。增强体含量较低时（0.5%），复合材料内部裂纹路径曲折，裂纹扩展过程中伴随着多条二次裂纹的萌生，穿晶断裂和沿晶断裂共存；高含量增强体会使得裂纹路径曲折度下降，裂纹变得平直，二次裂纹数量减少。因此，耐高温钛基复合材料增强体的断裂和其诱导的缺陷是裂纹扩展的重要因素，主要体现在裂纹扩展方向和二次裂纹的萌生。为实现高性能钛基复合材料的制备与安全加工，有效控制增强体的尺度和基体组织是高性能三元混杂颗粒增强钛基复合材料制备的关键。