【摘要】：隨著鈦合金在航空航天領(lǐng)域的廣泛應(yīng)用,鈦合金薄壁整體結(jié)構(gòu)件的需求日益迫切,液壓成形因其成形溫度低難以滿足鈦合金構(gòu)件的成形要求,而傳統(tǒng)的超塑性成形又因其成形溫度高,成形效率低,且對(duì)晶粒尺寸要求嚴(yán)格等因素極大地限制了鈦合金零件的生產(chǎn)應(yīng)用。為了解決鈦合金整體構(gòu)件成形難題,同時(shí)提高生產(chǎn)效率,提出熱態(tài)氣壓成形技術(shù),采用感應(yīng)加熱線圈快速加熱,以高壓氣體作為傳力介質(zhì),材料在高溫、內(nèi)部氣壓、管件端部沿軸向的壓力和模具內(nèi)壁共同作用下氣脹成形。熱態(tài)氣壓成形的鈦合金構(gòu)件具有回彈小、成形精度高、整體性好和可靠性高等優(yōu)點(diǎn)。因此,鈦合金熱態(tài)氣壓成形研究日漸成為鈦合金零件成形領(lǐng)域的前沿課題。TA15鈦合金在航空航天中應(yīng)用廣泛,高安全性和特殊的工作環(huán)境要求其構(gòu)件具有優(yōu)良的力學(xué)性能。TA15作為一種雙相多晶材料,其組織的多樣性導(dǎo)致了性能的不確定性,因此,研究其兩相、多晶之間相互協(xié)調(diào)變形機(jī)制與微觀組織演化機(jī)理,對(duì)于充分發(fā)揮其兩相多晶材料的優(yōu)點(diǎn),提高其綜合力學(xué)性能和改善塑性加工成形能力有重要的科學(xué)及工程意義。本課題通過系統(tǒng)研究不同熱處理制度下TA15的微觀組織,主要針對(duì)雙重退火后的雙態(tài)組織深入分析其熱變形機(jī)制和微觀組織演化機(jī)理,在此基礎(chǔ)上建立一套能夠預(yù)測(cè)微觀組織演變的統(tǒng)一粘塑性本構(gòu)模型,通過有限元及其二次開發(fā)技術(shù)實(shí)現(xiàn)TA15鈦合金管材熱態(tài)氣壓成形與微觀組織演變的模擬及預(yù)測(cè)。首先采用熱處理實(shí)驗(yàn)對(duì)不同熱處理制度下TA15的微觀組織進(jìn)行研究,分析了TA15在普通退火、再結(jié)晶退火與雙重退火三種退火制度下的力學(xué)性能、微觀組織以及拉伸斷口形貌,并定量研究了熱處理制度對(duì)相比例、成分及其形態(tài)的影響規(guī)律。研究得出TA15板材(950℃/2h/AC+600℃/2h/AC)雙重退火后獲得了良好的綜合力學(xué)性能。利用高溫拉伸實(shí)驗(yàn)研究了雙重退火后TA15的高溫變形行為,并通過求解熱激活方程分析了其熱變形機(jī)制。獲得了TA15的高溫流變曲線,分析表明其高溫拉伸變形是加工硬化、動(dòng)態(tài)軟化和塑性損傷之間相互影響共同作用的過程；研究了變形條件對(duì)峰值應(yīng)力、斷裂應(yīng)變與流變軟化的影響規(guī)律,為熱態(tài)氣壓成形工藝制定和工藝參數(shù)選擇提供實(shí)驗(yàn)依據(jù)和理論指導(dǎo)。采用掃描電鏡(SEM)、電子背散射衍射(EBSD)和透射電鏡(TEM)等微觀檢測(cè)技術(shù)觀察分析了雙態(tài)組織TA15鈦合金熱變形過程中的微觀組織演化規(guī)律和機(jī)理,定量研究了變形條件對(duì)片狀α相球化百分?jǐn)?shù)的影響規(guī)律。觀察分析了不同變形條件下TA15的晶體形貌與晶界-亞晶界組織分布,研究了變形條件對(duì)晶體形貌和晶界組織分布的影響規(guī)律；揭示了雙態(tài)組織的TA15熱變形微觀組織演化機(jī)理是由位錯(cuò)遷移和片狀α相的球化兩種機(jī)制共同決定的。基于統(tǒng)一粘塑性本構(gòu)理論,結(jié)合TA15熱變形微觀組織演化機(jī)理,考慮位錯(cuò)密度在熱變形中的演化規(guī)律、片狀α相球化規(guī)律以及兩相協(xié)調(diào)變形特征,建立了TA15熱變形本構(gòu)模型。通過遺傳算法優(yōu)化求解了模型材料常數(shù),實(shí)現(xiàn)了TA15高溫真應(yīng)力-應(yīng)變曲線和微觀組織演變的預(yù)測(cè)。該模型定量地描述了微觀組織與變形參數(shù)(應(yīng)力、應(yīng)變率、變形溫度等)之間的內(nèi)在關(guān)系,能夠反映TA15高溫變形本質(zhì)規(guī)律。采用應(yīng)力更新算法編寫了基于球化機(jī)理的統(tǒng)一粘塑性本構(gòu)模型VUMAT子程序；利用開發(fā)的VUMAT子程序,進(jìn)行TA15高溫拉伸有限元模擬分析,利用實(shí)驗(yàn)數(shù)據(jù)驗(yàn)證了有限元計(jì)算的真應(yīng)力-應(yīng)變曲線和片狀α相的球化曲線,證明了本構(gòu)模型有限元二次開發(fā)的有效性；利用二次開發(fā)的有限元模擬TA15管材熱態(tài)氣壓成形過程,分析了管材成形過程的應(yīng)力場(chǎng)、應(yīng)變場(chǎng)、厚度分布和球化程度,并摸索了工藝參數(shù)對(duì)TA15熱態(tài)氣壓成形與微觀組織的影響；最后進(jìn)行了TA15管材熱態(tài)氣壓成形實(shí)驗(yàn),對(duì)比驗(yàn)證了模型對(duì)熱態(tài)氣壓成形中厚度分布和球化程度的預(yù)測(cè)效果。通過有限元模擬及相關(guān)驗(yàn)證,說明所建立的基于球化機(jī)理的統(tǒng)一粘塑性本構(gòu)模型對(duì)熱態(tài)氣壓成形與微觀組織演變計(jì)算的準(zhǔn)確性和有效性,能夠把該模型運(yùn)用至鈦合金實(shí)際零件熱態(tài)氣壓成形與微觀組織的數(shù)值模擬過程中。本課題采用實(shí)驗(yàn)分析與建模仿真相結(jié)合的方法,研究揭示了兩相多晶材料TA15鈦合金的高溫變形行為與微觀組織演化機(jī)理,在此基礎(chǔ)上重點(diǎn)研究其熱態(tài)氣壓成形的本構(gòu)建模與微觀組織演化模擬,對(duì)TA15熱態(tài)氣壓成形工藝?yán)碚撗芯颗c實(shí)際生產(chǎn)有重要的科學(xué)及工程意義。
[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，

本文編號(hào)：2350917