本文關(guān)鍵詞： 鈦合金 微觀組織 力學(xué)性能 定量關(guān)系 有限元模型　出處：《西北工業(yè)大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：鈦合金高性能輕量化復(fù)雜整體構(gòu)件精確塑性成形成性一體化制造,是航空、航天等領(lǐng)域高端裝備發(fā)展越來越迫切的重要需求。如何精確描述鈦合金復(fù)雜的組織形態(tài)、分布及性能與宏觀性能的定量關(guān)系,從而對構(gòu)件組織和性能進(jìn)行有效調(diào)控,是其中的關(guān)鍵和挑戰(zhàn)性難題。為此,本文采用組織形態(tài)與分布定量表征、相組分本構(gòu)建模和基于真實(shí)組織的有限元建模仿真相結(jié)合的方法,以TA15鈦合金為對象,對其熱加工組織與性能精確定量關(guān)系進(jìn)行了系統(tǒng)深入的研究,主要研究內(nèi)容和結(jié)果如下:針對鈦合金微觀組織中等軸α相和片層α相之間復(fù)雜粘連難以定量表征的問題,采用凹點(diǎn)指示粘連位置、標(biāo)志圓和方向圓確定凹點(diǎn)配對的方法,并提出了確定正確分割線的準(zhǔn)則,從而建立了鈦合金復(fù)雜粘連組織自動分割的算法,分割正確率達(dá)85%以上。進(jìn)而提出了聯(lián)合采用體積分?jǐn)?shù)和軸比的自動識別等軸α相和片層α相的方法,識別正確率達(dá)95%以上。發(fā)展了鈦合金組織形態(tài)和分布的定量表征方法,提出采用面積法、平均截線法和橢圓擬合法分別定量表征組織的體積分?jǐn)?shù)、等軸α相尺寸和片層α相厚度;建立了行掃描和線段掃描算法,實(shí)現(xiàn)了線性路徑函數(shù)和兩點(diǎn)關(guān)系函數(shù)對組織形態(tài)和分布的高效定量表征,計(jì)算效率提高30倍。揭示了TA15鈦合金組織演化與熱加工參數(shù)的定量關(guān)系,發(fā)現(xiàn)兩步熱處理和等溫壓縮促使片層α相厚度增加,兩步熱處理以及等溫壓縮+低于變形溫度10℃和25℃熱處理促使三次α相析出;等溫壓縮后等軸α相和片層α相分別在0°(垂直于壓縮方向)和45°方向集中分布;熱處理后等軸α相各向分布均勻,而片層α相各向分布不均勻。定量揭示了熱加工過程中特征組織性能的變化規(guī)律及其對TA15鈦合金宏觀性的影響規(guī)律,發(fā)現(xiàn)等溫壓縮后轉(zhuǎn)變β基體硬度從雙態(tài)組織到三態(tài)組織增加0.1-0.4GPa,等軸α相的硬度變化不大;β基體對TA15合金硬度的貢獻(xiàn)大于55%,等軸α-β基體界面的貢獻(xiàn)小于8%,等軸α相和片層α相-殘余β相界面的貢獻(xiàn)在8%-40%之間;雙態(tài)和三態(tài)組織中細(xì)片層α相變形不均勻,合金的延伸率較低;三態(tài)組織中粗、細(xì)片層α相混合組織變形相對均勻,合金的延伸率較高。發(fā)展了基于TA15鈦合金微觀結(jié)構(gòu)的有限元幾何建模方法,考慮位錯(cuò)強(qiáng)化和固溶強(qiáng)化以及對納米壓痕曲線進(jìn)行逆向分析,分別建立了等軸α相和轉(zhuǎn)變β基體的本構(gòu)關(guān)系。從而建立了基于TA15鈦合金真實(shí)微觀組織的有限元模型。通過應(yīng)力-應(yīng)變曲線以及微觀組織變形特征驗(yàn)證了模型的可靠性。研究了組織參數(shù)對TA15鈦合金宏觀性能的影響規(guī)律,發(fā)現(xiàn)等軸α相含量減少40%,合金抗拉強(qiáng)度提高18%;沿等軸α相定向分布方向合金抗拉強(qiáng)度高;等軸α相屈服強(qiáng)度提高12%,合金抗拉強(qiáng)度提高較小,失效應(yīng)變提高25%;轉(zhuǎn)變β基體屈服強(qiáng)度增加18%,由于應(yīng)變集中程度增加,TA15合金的抗拉強(qiáng)度提高10%,失效應(yīng)變降低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 偽 phase and lamellar 偽 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 偽 phase and lamellar 偽 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 偽 phase size and lamellar 偽 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 偽 phase. Two-step heat treatment and isothermal compression below the deformation temperature of 10 鈩，

本文編號：1460033