基于建模的TA15钛合金组织—性能定量关系研究

发布时间：2018-01-24 12:19

  本文关键词： 钛合金 微观组织 力学性能 定量关系 有限元模型　出处：《西北工业大学》2015年博士论文　论文类型：学位论文

【摘要】：钛合金高性能轻量化复杂整体构件精确塑性成形成性一体化制造,是航空、航天等领域高端装备发展越来越迫切的重要需求。如何精确描述钛合金复杂的组织形态、分布及性能与宏观性能的定量关系,从而对构件组织和性能进行有效调控,是其中的关键和挑战性难题。为此,本文采用组织形态与分布定量表征、相组分本构建模和基于真实组织的有限元建模仿真相结合的方法,以TA15钛合金为对象,对其热加工组织与性能精确定量关系进行了系统深入的研究,主要研究内容和结果如下:针对钛合金微观组织中等轴α相和片层α相之间复杂粘连难以定量表征的问题,采用凹点指示粘连位置、标志圆和方向圆确定凹点配对的方法,并提出了确定正确分割线的准则,从而建立了钛合金复杂粘连组织自动分割的算法,分割正确率达85%以上。进而提出了联合采用体积分数和轴比的自动识别等轴α相和片层α相的方法,识别正确率达95%以上。发展了钛合金组织形态和分布的定量表征方法,提出采用面积法、平均截线法和椭圆拟合法分别定量表征组织的体积分数、等轴α相尺寸和片层α相厚度;建立了行扫描和线段扫描算法,实现了线性路径函数和两点关系函数对组织形态和分布的高效定量表征,计算效率提高30倍。揭示了TA15钛合金组织演化与热加工参数的定量关系,发现两步热处理和等温压缩促使片层α相厚度增加,两步热处理以及等温压缩+低于变形温度10℃和25℃热处理促使三次α相析出;等温压缩后等轴α相和片层α相分别在0°(垂直于压缩方向)和45°方向集中分布;热处理后等轴α相各向分布均匀,而片层α相各向分布不均匀。定量揭示了热加工过程中特征组织性能的变化规律及其对TA15钛合金宏观性的影响规律,发现等温压缩后转变β基体硬度从双态组织到三态组织增加0.1-0.4GPa,等轴α相的硬度变化不大;β基体对TA15合金硬度的贡献大于55%,等轴α-β基体界面的贡献小于8%,等轴α相和片层α相-残余β相界面的贡献在8%-40%之间;双态和三态组织中细片层α相变形不均匀,合金的延伸率较低;三态组织中粗、细片层α相混合组织变形相对均匀,合金的延伸率较高。发展了基于TA15钛合金微观结构的有限元几何建模方法,考虑位错强化和固溶强化以及对纳米压痕曲线进行逆向分析,分别建立了等轴α相和转变β基体的本构关系。从而建立了基于TA15钛合金真实微观组织的有限元模型。通过应力-应变曲线以及微观组织变形特征验证了模型的可靠性。研究了组织参数对TA15钛合金宏观性能的影响规律,发现等轴α相含量减少40%,合金抗拉强度提高18%;沿等轴α相定向分布方向合金抗拉强度高;等轴α相屈服强度提高12%,合金抗拉强度提高较小,失效应变提高25%;转变β基体屈服强度增加18%,由于应变集中程度增加,TA15合金的抗拉强度提高10%,失效应变降低36%。
[Abstract]:Titanium alloy high performance lightweight complex integral component precise plastic formative integration manufacturing is aviation. The development of high-end equipment in aerospace is becoming more and more urgent. How to accurately describe the complex microstructure, distribution and properties of titanium alloys and the quantitative relationship between the properties and macroscopic properties. In order to effectively regulate the structure and performance of components, it is a key and challenging problem. Therefore, the quantitative characterization of organizational morphology and distribution is adopted in this paper. Based on the combination of phase component modeling and finite element modeling and simulation, the accurate quantitative relationship between hot working microstructure and properties of TA15 titanium alloy was studied systematically and deeply. The main contents and results are as follows: aiming at the problem that the complex adhesion between 伪 phase and lamellar 伪 phase of titanium alloy microstructure is difficult to be quantitatively characterized, the concave point is used to indicate the adhesion position. The marking circle and direction circle are used to determine the concave point pairing, and the criterion of determining the correct split-line is put forward, thus the automatic segmentation algorithm of complex adhesion tissue of titanium alloy is established. The segmentation accuracy is more than 85%. A method of automatic recognition of equiaxed 伪 phase and lamellar 伪 phase by volume fraction and axial ratio is proposed. The recognition accuracy is more than 95%. The quantitative characterization method of microstructure morphology and distribution of titanium alloy has been developed. The area method, the average truncation method and the elliptical fitting method have been used to quantitatively characterize the volume fraction of the tissue, respectively. Equiaxed 伪 phase size and lamellar 伪 phase thickness; The algorithms of line scanning and line segment scanning are established, and the linear path function and two point relation function are used to describe the shape and distribution of the tissue. The quantitative relationship between microstructure evolution and hot working parameters of TA15 titanium alloy is revealed. It is found that two-step heat treatment and isothermal compression increase the thickness of 伪 phase. Two-step heat treatment and isothermal compression below the deformation temperature of 10 鈩，

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