基于球化机理TA15钛合金热态气压成形微观组织建模仿真
发布时间：2018-11-23 08:29
【摘要】：随着钛合金在航空航天领域的广泛应用,钛合金薄壁整体结构件的需求日益迫切,液压成形因其成形温度低难以满足钛合金构件的成形要求,而传统的超塑性成形又因其成形温度高,成形效率低,且对晶粒尺寸要求严格等因素极大地限制了钛合金零件的生产应用。为了解决钛合金整体构件成形难题,同时提高生产效率,提出热态气压成形技术,采用感应加热线圈快速加热,以高压气体作为传力介质,材料在高温、内部气压、管件端部沿轴向的压力和模具内壁共同作用下气胀成形。热态气压成形的钛合金构件具有回弹小、成形精度高、整体性好和可靠性高等优点。因此,钛合金热态气压成形研究日渐成为钛合金零件成形领域的前沿课题。TA15钛合金在航空航天中应用广泛,高安全性和特殊的工作环境要求其构件具有优良的力学性能。TA15作为一种双相多晶材料,其组织的多样性导致了性能的不确定性,因此,研究其两相、多晶之间相互协调变形机制与微观组织演化机理,对于充分发挥其两相多晶材料的优点,提高其综合力学性能和改善塑性加工成形能力有重要的科学及工程意义。本课题通过系统研究不同热处理制度下TA15的微观组织,主要针对双重退火后的双态组织深入分析其热变形机制和微观组织演化机理,在此基础上建立一套能够预测微观组织演变的统一粘塑性本构模型,通过有限元及其二次开发技术实现TA15钛合金管材热态气压成形与微观组织演变的模拟及预测。首先采用热处理实验对不同热处理制度下TA15的微观组织进行研究,分析了TA15在普通退火、再结晶退火与双重退火三种退火制度下的力学性能、微观组织以及拉伸断口形貌,并定量研究了热处理制度对相比例、成分及其形态的影响规律。研究得出TA15板材(950℃/2h/AC+600℃/2h/AC)双重退火后获得了良好的综合力学性能。利用高温拉伸实验研究了双重退火后TA15的高温变形行为,并通过求解热激活方程分析了其热变形机制。获得了TA15的高温流变曲线,分析表明其高温拉伸变形是加工硬化、动态软化和塑性损伤之间相互影响共同作用的过程；研究了变形条件对峰值应力、断裂应变与流变软化的影响规律,为热态气压成形工艺制定和工艺参数选择提供实验依据和理论指导。采用扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM)等微观检测技术观察分析了双态组织TA15钛合金热变形过程中的微观组织演化规律和机理,定量研究了变形条件对片状α相球化百分数的影响规律。观察分析了不同变形条件下TA15的晶体形貌与晶界-亚晶界组织分布,研究了变形条件对晶体形貌和晶界组织分布的影响规律；揭示了双态组织的TA15热变形微观组织演化机理是由位错迁移和片状α相的球化两种机制共同决定的。基于统一粘塑性本构理论,结合TA15热变形微观组织演化机理,考虑位错密度在热变形中的演化规律、片状α相球化规律以及两相协调变形特征,建立了TA15热变形本构模型。通过遗传算法优化求解了模型材料常数,实现了TA15高温真应力-应变曲线和微观组织演变的预测。该模型定量地描述了微观组织与变形参数(应力、应变率、变形温度等)之间的内在关系,能够反映TA15高温变形本质规律。采用应力更新算法编写了基于球化机理的统一粘塑性本构模型VUMAT子程序；利用开发的VUMAT子程序,进行TA15高温拉伸有限元模拟分析,利用实验数据验证了有限元计算的真应力-应变曲线和片状α相的球化曲线,证明了本构模型有限元二次开发的有效性；利用二次开发的有限元模拟TA15管材热态气压成形过程,分析了管材成形过程的应力场、应变场、厚度分布和球化程度,并摸索了工艺参数对TA15热态气压成形与微观组织的影响；最后进行了TA15管材热态气压成形实验,对比验证了模型对热态气压成形中厚度分布和球化程度的预测效果。通过有限元模拟及相关验证,说明所建立的基于球化机理的统一粘塑性本构模型对热态气压成形与微观组织演变计算的准确性和有效性,能够把该模型运用至钛合金实际零件热态气压成形与微观组织的数值模拟过程中。本课题采用实验分析与建模仿真相结合的方法,研究揭示了两相多晶材料TA15钛合金的高温变形行为与微观组织演化机理,在此基础上重点研究其热态气压成形的本构建模与微观组织演化模拟,对TA15热态气压成形工艺理论研究与实际生产有重要的科学及工程意义。
[Abstract]:With the wide application of the titanium alloy in the field of aeronautics and astronautics, the requirement of the thin-wall integral structure of the titanium alloy is becoming more and more urgent, and the hydraulic forming is difficult to meet the forming requirement of the titanium alloy component due to the low forming temperature of the titanium alloy, and the traditional superplastic forming has the advantages of high forming temperature and low forming efficiency. and the production and application of the titanium alloy parts are greatly limited by the factors such as the strict grain size requirement. in ord to solve that problem of forming the integral component of the titanium alloy, improve the production efficiency, and the end part of the pipe is expanded and formed under the action of the pressure in the axial direction and the inner wall of the die. The hot-state pressure-forming titanium alloy component has the advantages of small rebound, high forming precision, good integrity, high reliability and the like. Therefore, the study of the hot-state pressure forming of the titanium alloy has become a leading topic in the field of the forming of titanium alloy parts. The TA15 titanium alloy has wide application, high safety and special working environment in the aerospace, and its components have excellent mechanical properties. TA15 as a two-phase polycrystalline material, the diversity of its structure leads to the uncertainty of the performance, and therefore, the mechanism of the mutual coordination between the two phases and the polycrystal and the mechanism of the microstructure evolution is studied, and the advantages of the two-phase polycrystalline material can be fully exerted, and has important scientific and engineering significance for improving the comprehensive mechanical property and improving the plastic processing and forming capacity. In this paper, the microstructure of TA15 under different heat treatment system is studied by the system, and the mechanism of thermal deformation and the mechanism of microstructure evolution of the double-state tissue after double annealing are analyzed, and a unified viscoplastic model for predicting the evolution of microstructure is established. The simulation and prediction of the thermal state pressure forming and microstructure evolution of the TA15 titanium alloy tube are realized by the finite element and the secondary development technology. The microstructure of TA15 under different heat treatment regimes was studied by heat treatment experiment, and the mechanical properties, microstructure and tensile fracture morphology of TA15 under the three annealing conditions of common annealing, recrystallization annealing and double annealing were analyzed. The influence of heat treatment system on the phase proportion, composition and its morphology was studied quantitatively. A good comprehensive mechanical property was obtained after the double annealing of TA15 plate (950 鈩，
本文编号：2350917
[Abstract]:With the wide application of the titanium alloy in the field of aeronautics and astronautics, the requirement of the thin-wall integral structure of the titanium alloy is becoming more and more urgent, and the hydraulic forming is difficult to meet the forming requirement of the titanium alloy component due to the low forming temperature of the titanium alloy, and the traditional superplastic forming has the advantages of high forming temperature and low forming efficiency. and the production and application of the titanium alloy parts are greatly limited by the factors such as the strict grain size requirement. in ord to solve that problem of forming the integral component of the titanium alloy, improve the production efficiency, and the end part of the pipe is expanded and formed under the action of the pressure in the axial direction and the inner wall of the die. The hot-state pressure-forming titanium alloy component has the advantages of small rebound, high forming precision, good integrity, high reliability and the like. Therefore, the study of the hot-state pressure forming of the titanium alloy has become a leading topic in the field of the forming of titanium alloy parts. The TA15 titanium alloy has wide application, high safety and special working environment in the aerospace, and its components have excellent mechanical properties. TA15 as a two-phase polycrystalline material, the diversity of its structure leads to the uncertainty of the performance, and therefore, the mechanism of the mutual coordination between the two phases and the polycrystal and the mechanism of the microstructure evolution is studied, and the advantages of the two-phase polycrystalline material can be fully exerted, and has important scientific and engineering significance for improving the comprehensive mechanical property and improving the plastic processing and forming capacity. In this paper, the microstructure of TA15 under different heat treatment system is studied by the system, and the mechanism of thermal deformation and the mechanism of microstructure evolution of the double-state tissue after double annealing are analyzed, and a unified viscoplastic model for predicting the evolution of microstructure is established. The simulation and prediction of the thermal state pressure forming and microstructure evolution of the TA15 titanium alloy tube are realized by the finite element and the secondary development technology. The microstructure of TA15 under different heat treatment regimes was studied by heat treatment experiment, and the mechanical properties, microstructure and tensile fracture morphology of TA15 under the three annealing conditions of common annealing, recrystallization annealing and double annealing were analyzed. The influence of heat treatment system on the phase proportion, composition and its morphology was studied quantitatively. A good comprehensive mechanical property was obtained after the double annealing of TA15 plate (950 鈩，
本文编号：2350917
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