本文選題：枝晶 + 相場(chǎng)模型�。� 參考：《中北大學(xué)》2017年碩士論文

【摘要】：枝晶作為金屬晶體中的最基本結(jié)構(gòu),枝晶的生長(zhǎng)過程對(duì)于金屬鑄件凝固組織的形成具有決定性作用。微觀組織數(shù)值模擬作為一個(gè)新興科學(xué),由于其在金屬枝晶生長(zhǎng)及鑄件成形過程模擬上擁有的獨(dú)特優(yōu)勢(shì)而備受關(guān)注,它不僅能夠有效地補(bǔ)充、完善金屬凝固理論,而且能夠指導(dǎo)實(shí)際生產(chǎn)從而降低工藝改進(jìn)的成本。本文利用改進(jìn)的相場(chǎng)模型對(duì)Fe-C合金進(jìn)行了以下幾個(gè)方面的研究。(1)利用改進(jìn)的相場(chǎng)模型進(jìn)行了枝晶生長(zhǎng)過程的三維模擬。在相場(chǎng)理論的基礎(chǔ)上,研究了相場(chǎng)模型參數(shù)(包括界面厚度、弛豫時(shí)間等)對(duì)于枝晶生長(zhǎng)過程及最終形貌的影響,并確定合適的相場(chǎng)模型參數(shù)。(2)對(duì)等軸枝晶生長(zhǎng)過程中枝晶尖端參數(shù)進(jìn)行了分析,模擬結(jié)果與現(xiàn)有枝晶生長(zhǎng)理論以及實(shí)驗(yàn)結(jié)果相一致。同時(shí)通過控制枝晶尖端過飽和度實(shí)現(xiàn)了成分過冷對(duì)枝晶尖端參數(shù)影響的定量化分析研究。(3)對(duì)等溫凝固過程中等軸枝晶的生長(zhǎng)過程進(jìn)行三維模擬。利用耦合界面能各向異性的相場(chǎng)模型,研究了界面能各向異性對(duì)于枝晶生長(zhǎng)過程的影響,并成功地模擬出Fe-C合金等軸晶生長(zhǎng)過程中所存在的枝晶取向轉(zhuǎn)變過程。(4)對(duì)定向凝固過程中枝晶的生長(zhǎng)過程進(jìn)行了分析,主要研究了推進(jìn)速度、溫度梯度對(duì)定向凝固過程的影響。通過調(diào)整定向凝固模擬過程中合金界面能各向異性系數(shù)實(shí)現(xiàn)對(duì)于不同含量的Fe-C合金定向凝固過程研究,成功模擬出定向凝固過程中所形成的的液相通道以及對(duì)應(yīng)的溶質(zhì)偏析現(xiàn)象,并系統(tǒng)的研究了定向凝固過程參數(shù)對(duì)于液相通道的形成以及整體枝晶形貌的影響。
[Abstract]:Dendrite is the most basic structure in metal crystals, and the growth process of dendrite plays a decisive role in the formation of solidification structure of metal castings. As a new science, numerical simulation of microstructure has attracted much attention because of its unique advantages in metal dendrite growth and simulation of casting forming process. It can not only effectively complement and perfect the theory of metal solidification. And can guide the actual production to reduce the cost of process improvement. In this paper, the improved phase field model is used to study the Fe-C alloy in the following aspects. 1) Three-dimensional simulation of dendritic growth process is carried out using the improved phase field model. Based on the phase field theory, the effects of phase field model parameters (including interface thickness, relaxation time, etc.) on the dendritic growth process and final morphology are studied. The parameters of dendritic tip in the process of iso-axial dendritic growth are analyzed. The simulation results are in agreement with the existing dendritic growth theory and experimental results. At the same time, by controlling the supersaturation of dendritic tip, the quantitative analysis of the effect of component undercooling on the dendritic tip parameters is carried out. The three-dimensional simulation of isometric dendritic growth during isothermal solidification is carried out. The effect of interfacial energy anisotropy on dendritic growth is studied by using the phase field model of coupling interface energy anisotropy. The dendritic orientation transformation process of Fe-C alloy during equiaxed crystal growth was successfully simulated. The dendritic growth process during directional solidification was analyzed. The effects of advancing speed and temperature gradient on the directional solidification process were studied. By adjusting the anisotropy coefficient of interface energy in the simulation of directional solidification, the directional solidification process of Fe-C alloy with different content is studied. The liquid channel formed during directional solidification and the corresponding solute segregation were successfully simulated, and the effects of directional solidification parameters on the formation of liquid channel and the morphology of dendrite were systematically studied.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG111.4

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