【摘要】：熱加工作為一種常用的塑性成形方法,廣泛地應(yīng)用于鋁、鐵、鈦等合金零件的制備。而動態(tài)再結(jié)晶(Dynamic recrystallization,DRX)作為熱加工中重要的晶粒細(xì)化和軟化機制,對于材料變形組織控制、塑性成形能力改善和成形工藝(如鍛造、擠壓、沖壓等)優(yōu)化具有重要的工程應(yīng)用價值。傳統(tǒng)采用的理論與實驗的研究方法無法實時定量地獲得材料微觀組織的演化信息,元胞自動機(Cellular Automaton,CA)因具有作用規(guī)則簡單,計算高效以及具有真實的物理意義,故被廣泛地應(yīng)用于金屬材料動態(tài)再結(jié)晶過程的組織演化模擬中。V-10Cr-5Ti合金具有良好的抗輻照性能、抗氫脆性、耐熱性、可加工性,同時具有強度高和熱膨脹性低等優(yōu)良性能,是核聚變反應(yīng)堆的候選材料。本研究采用元胞自動機法研究V-10Cr-5Ti合金熱變形過程的微觀組織演化,探究其DRX行為及工藝參數(shù)對顯微組織演變規(guī)律的影響。通過V-10Cr-5Ti合金的等溫?zé)釅嚎s實驗獲得變形溫度950~1350℃、應(yīng)變速率0.01~10s-1范圍內(nèi)的流動應(yīng)力曲線,研究了其熱塑性流動特點。建立了包含應(yīng)變的雙曲正弦Arrhenius模型,并對模型預(yù)測的效果開展了評估,結(jié)果表明所建立的本構(gòu)模型具有良好的預(yù)測精度,適用于CA法模擬微觀組織演化的研究。構(gòu)建了CA法基礎(chǔ)模型并耦合了材料物理過程的內(nèi)在規(guī)則作用模型,如:熱激活原則、晶界遷移、曲率驅(qū)動和能量耗散。開發(fā)與調(diào)試初始化組織程序,生成初始化組織。初始化模擬結(jié)果與實驗對比,結(jié)果發(fā)現(xiàn)兩者具有較好的一致性,驗證所建立的CA模型的準(zhǔn)確性與適用性,同時也為后續(xù)V-10Cr-5Ti合金DRX研究開展奠定了理論基礎(chǔ)。構(gòu)建了V-10Cr-5Ti合金熱塑性變形過程中的拓?fù)鋵W(xué)模型,對試樣的不同變形區(qū)進行了驗證,結(jié)果顯示兩者吻合良好,同時對不同變形區(qū)晶粒的形態(tài)學(xué)開展了分析。在所建立的位錯密度模型、再結(jié)晶形核模型、晶粒長大模型和臨界位錯密度模型的基礎(chǔ)上,開發(fā)了基于元胞自動機的V-10Cr-5Ti合金DRX過程組織模擬演化的核心程序。利用所建立的模型,實現(xiàn)了對不同工藝參數(shù)下顯微組織演變的數(shù)值模擬,結(jié)合顯微組織觀察,結(jié)果表明模擬與實驗數(shù)據(jù)誤差較小,說明所建立的CA模型能夠較好地適用于V-10Cr-5Ti合金DRX過程組織演化的預(yù)測。此外,基于此模型,研究了不同初始晶粒尺寸、變形溫度、應(yīng)變速率以及應(yīng)變量等參數(shù)對V-10Cr-5Ti合金DRX過程的影響,闡明了DRX過程中工藝對組織演化的內(nèi)在機理。
[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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.413;TG306

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