Ti-Al层状金属复合材料的增强增韧机理与力学行为研究

发布时间：2018-04-21 08:02

本文选题：层状复合材料 + 钛多晶　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：层状Ti-Al复合板由交替排列的强度较高的钛层和塑性好的铝层通过热压-轧制而成,这种材料能够结合两种材料的性能优势,弥补单一的金属材料的某些方面的不足,表现出更优良的特性。本课题主要对Ti-Al层状金属复合材料中钛层的力学行为和复合材料的增强增韧机理进行研究。采用塑性细观力学方法编写程序对钛弹塑性变形过程进行数值分析。之后选取合理的韧性破坏准则分析其韧性破坏失效过程和增韧机理。在此基础上引入铝层弹塑性变形的宏观本构关系以及缺陷层理论,分析随着各相层厚比变化,Ti-Al层状金属复合材料的增强增韧机制。本文首先介绍了晶体学基本理论、多晶体塑性变形的基本理论以及金属材料变形的韧性破坏准则。根据钛晶格常数等特点和钛合金塑性变形研究的相关实验得到影响金属钛塑性变形过程的主要变形机制是滑移和孪生,一般数值分析过程重点考虑滑移机制。将林同骅模型进行改进分析推导得到适用于描述多晶体钛的弹塑性变形过程的塑性细观力学模型。在此基础上编写程序对多晶钛的弹塑性变形进行数值分析得到能够体现多晶体钛细观变形特点的应力应变关系。这一塑性细观力学模型可以更好的应用于数值分析密排六方晶体的弹塑性变形过程。之后研究了描述金属材料韧性破坏的断裂准则,通过对实验结果的观察分析得到钛断裂形式为微孔聚集型断裂。选取Rice-Tracey韧性断裂模型使用阀值控制的方法来描述材料韧性破坏行为,合理的描述了多晶钛的失效行为。进一步改变加载过程,对不同应力状态下钛单轴拉伸进行数值分析,使用韧性断裂准则分析不同应力状态后钛单轴拉伸的结果,得到不同应力作用下断裂韧性值C随应变变化关系。发现对应于同一应变量,有外部应力作用与无外部应力相比韧性断裂值C明显减小了,约束状态越强,韧性断裂值C减小越明显,同时韧性断裂值C随着拉伸方向应变不断增大的趋势也减小了。这一分析结果表明在钛薄板拉伸过程中垂直于板面方向一定形式的应力作用对于其整体的拉伸有较好的增韧效果。最后引入铝层弹塑性变形的宏观本构关系和缺陷层模型,得到均匀介质层和考虑缺陷层模型下的不同层厚比的层状金属复合板拉伸的应力应变关系。使用韧性断裂准则分析考虑缺陷层时不同厚度比的层状金属复合板的断裂韧性。发现一定范围内,钛层的含量越高,缺陷层对于钛拉伸破坏的影响减小了,从而解释了随着钛层和铝层厚度比的增大,复合材料的增强增韧机制。
[Abstract]:The laminated Ti-Al composite plate is composed of titanium layer with high strength arranged alternately and aluminum layer with good plasticity by hot-pressing rolling. This material can combine the performance advantages of the two kinds of materials and make up for the deficiency of some aspects of a single metal material. Show better characteristics. In this paper, the mechanical behavior of titanium layer and the reinforcing and toughening mechanism of Ti-Al laminated metal composites are studied. The plastic meso-mechanical method is used to program the elastic plastic deformation of titanium. Then the failure process and toughening mechanism of ductile failure are analyzed by selecting reasonable ductile failure criterion. On the basis of this, the macroscopic constitutive relation of elastoplastic deformation of aluminum layer and the theory of defect layer are introduced, and the reinforcing and toughening mechanism of Ti-Al laminated metal composite is analyzed with the change of the thickness ratio of each phase layer. In this paper, the basic theory of crystallography, the basic theory of polycrystalline plastic deformation and the ductile failure criterion of metal materials are introduced. According to the characteristics of titanium lattice constants and the relevant experiments on the plastic deformation of titanium alloys, the main deformation mechanisms affecting the plastic deformation of titanium alloys are slip and twinning. The general numerical analysis focuses on the slip mechanism. Based on the improved analysis of Lin Tonghua model, a plastic meso-mechanical model suitable for describing the elastoplastic deformation process of polycrystalline titanium is derived. On this basis, a program is written to analyze the elastoplastic deformation of polycrystalline titanium by numerical analysis, and the stress-strain relationship which can reflect the characteristics of meso-deformation of polycrystalline titanium is obtained. This plastic mesomechanical model can be applied to the numerical analysis of elastic-plastic deformation process of dense hexagonal crystals. Then the fracture criterion describing the ductile failure of metallic materials is studied. By observing and analyzing the experimental results, it is found that the fracture form of titanium is microporous aggregate fracture. The Rice-Tracey ductile fracture model is selected to describe the toughness failure behavior of the material by using the threshold control method, and the failure behavior of polycrystalline titanium is described reasonably. Further changing the loading process, the uniaxial tension of titanium under different stress states is numerically analyzed, and the results of uniaxial tension of titanium under different stress states are analyzed by using the ductile fracture criterion. The relationship of fracture toughness C with strain under different stress is obtained. It is found that the ductile fracture value C decreases obviously when the external stress is applied to the same strain, and the stronger the constrained state is, the more obvious the ductile fracture value C decreases. At the same time, the ductile fracture value C decreases with the strain increasing in the tensile direction. The results show that a certain form of stress acting perpendicular to the plate during the tensile process of the titanium sheet has a good toughening effect on the overall tensile strength of the titanium sheet. Finally, the macroscopic constitutive relation and defect layer model of elastic-plastic deformation of aluminum layer are introduced to obtain the stress-strain relationship between uniform medium layer and laminated metal composite plate with different thickness ratios under the model of defect layer. The ductile fracture criterion is used to analyze the fracture toughness of laminated metal clad plates with different thickness ratio when the defect layer is considered. It is found that the higher the content of titanium layer, the less the effect of defect layer on tensile fracture of titanium, which explains the reinforcing and toughening mechanism of composites with the increase of thickness ratio of titanium layer to aluminum layer.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB331

【参考文献】