V-10Cr-5Ti合金热变形行为及动态再结晶组织演化模拟

发布时间：2019-06-19 16:04

【摘要】：热加工作为一种常用的塑性成形方法,广泛地应用于铝、铁、钛等合金零件的制备。而动态再结晶(Dynamic recrystallization,DRX)作为热加工中重要的晶粒细化和软化机制,对于材料变形组织控制、塑性成形能力改善和成形工艺(如锻造、挤压、冲压等)优化具有重要的工程应用价值。传统采用的理论与实验的研究方法无法实时定量地获得材料微观组织的演化信息,元胞自动机(Cellular Automaton,CA)因具有作用规则简单,计算高效以及具有真实的物理意义,故被广泛地应用于金属材料动态再结晶过程的组织演化模拟中。V-10Cr-5Ti合金具有良好的抗辐照性能、抗氢脆性、耐热性、可加工性,同时具有强度高和热膨胀性低等优良性能,是核聚变反应堆的候选材料。本研究采用元胞自动机法研究V-10Cr-5Ti合金热变形过程的微观组织演化,探究其DRX行为及工艺参数对显微组织演变规律的影响。通过V-10Cr-5Ti合金的等温热压缩实验获得变形温度950~1350℃、应变速率0.01~10s-1范围内的流动应力曲线,研究了其热塑性流动特点。建立了包含应变的双曲正弦Arrhenius模型,并对模型预测的效果开展了评估,结果表明所建立的本构模型具有良好的预测精度,适用于CA法模拟微观组织演化的研究。构建了CA法基础模型并耦合了材料物理过程的内在规则作用模型,如:热激活原则、晶界迁移、曲率驱动和能量耗散。开发与调试初始化组织程序,生成初始化组织。初始化模拟结果与实验对比,结果发现两者具有较好的一致性,验证所建立的CA模型的准确性与适用性,同时也为后续V-10Cr-5Ti合金DRX研究开展奠定了理论基础。构建了V-10Cr-5Ti合金热塑性变形过程中的拓扑学模型,对试样的不同变形区进行了验证,结果显示两者吻合良好,同时对不同变形区晶粒的形态学开展了分析。在所建立的位错密度模型、再结晶形核模型、晶粒长大模型和临界位错密度模型的基础上,开发了基于元胞自动机的V-10Cr-5Ti合金DRX过程组织模拟演化的核心程序。利用所建立的模型,实现了对不同工艺参数下显微组织演变的数值模拟,结合显微组织观察,结果表明模拟与实验数据误差较小,说明所建立的CA模型能够较好地适用于V-10Cr-5Ti合金DRX过程组织演化的预测。此外,基于此模型,研究了不同初始晶粒尺寸、变形温度、应变速率以及应变量等参数对V-10Cr-5Ti合金DRX过程的影响,阐明了DRX过程中工艺对组织演化的内在机理。
[Abstract]:As a common plastic forming method, hot working is widely applied to the preparation of alloy parts such as aluminum, iron, titanium and the like. Dynamic Recrystallization (DRX), as an important grain refining and softening mechanism in hot working, has important engineering application value for the optimization of material deformation tissue, the improvement of the plastic forming ability and the optimization of the forming process (such as forging, extrusion, stamping, etc.). The traditional theory and experimental research method can not quantitatively obtain the evolution information of the micro-structure of the material in real time, and the cellular automaton (CA) has the advantages of simple rule, high calculation efficiency and real physical significance. And is widely applied to the tissue evolution simulation of the dynamic recrystallization process of the metal material. The V-10Cr-5Ti alloy has good anti-irradiation property, hydrogen embrittlement resistance, heat resistance and processability, and has excellent properties such as high strength and thermal expansion, and is a candidate material for nuclear fusion reactor. The microstructure evolution of the thermal deformation of V-10Cr-5Ti alloy is studied by the cellular automaton method, and the influence of the DRX behavior and process parameters on the evolution of the microstructure is investigated. The flow stress curves in the range of 950 to 1350.degree. C. and the strain rate of 0.01 to 10 s-1 were obtained by isothermal compression experiments of V-10Cr-5Ti alloy, and the characteristics of the thermoplastic flow were studied. The hyperbolic sine Arrhenius model with strain is established, and the effect of the model prediction is evaluated. The results show that the established constitutive model has good prediction precision and is suitable for the research of the simulation of microstructure evolution by the CA method. The basic model of CA method is built and the internal regular function model of material physical process is coupled, such as thermal activation principle, grain boundary migration, curvature driving and energy dissipation. Develop and debug the initialization organization program to generate the initialization organization. The simulation results are compared with the experiment, and the result shows that the two have good consistency, and the accuracy and the applicability of the established CA model are verified, and the theoretical basis for the follow-up V-10Cr-5Ti alloy DRX research is also established. In this paper, the mechanical model of V-10Cr-5Ti alloy is constructed, and the different deformation areas of the sample are verified. The results show that the two are in good agreement with each other, and the morphology of the grains in different deformation areas is analyzed. On the basis of the established dislocation density model, the recrystallization nucleation model, the grain growth model and the critical dislocation density model, the core program for the simulation and evolution of the V-10Cr-5Ti alloy DRX process based on the cellular automaton was developed. The numerical simulation of microstructure evolution under different process parameters is realized by using the established model, and the results show that the simulation and experimental data error are small, and the established CA model can be well applied to the prediction of the evolution of the V-10Cr-5Ti alloy DRX process. In addition, on the basis of this model, the influence of different initial grain size, deformation temperature, strain rate and the corresponding variable on the DRX process of V-10Cr-5Ti alloy is studied, and the internal mechanism of the process to the evolution of the structure in the DRX process is clarified.
【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】：2017
【分类号】：TG146.413;TG306

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