镍铝高温合金强化相沉淀行为研究
毕业论文关键词：Ni-Al 高温合金，沉淀，相场，微观组织，粗化
Title The precipitation behavior research of Ni-Al superalloys' strengthening phase
Abstract Ni-based superalloys are widely used in the aerospace field owing to their excellent strength, toughness, fatigue performance, oxidation and thermal corrosion performance at high temperatures. The strength of Ni-Al alloy depends on the morphology, size, volume fraction and spatial distribution of strengthening phase（γ′ phase）. Thus, the research of the morphology evolution and the coarsening behavior of γ′ phase are essential for improving performance of alloy. Based on the Phase-field model, by using the periodic boundary conditions, Ginzburg-Landau and Cahn-Hilliard kinetic equation is solved with a semi-implicit fourier-spectral method. With Matlab7.0 programming, We investigated the microstructure evolution at different temperatures and the effects of temperature on the phase component, order parameter, the volume fraction and coarsening behavior of γ′ phase in Ni-Al superalloys. With the decrease of the aging temperature, the γ′ phase morphology changes from separated cuboidal to connected rectangle shape. On the one hand，there is Ostward ripening；on the other hand，the γ′ phase constantly growing up, coarsening and connection. The coarsening rate of γ′ phase decreases. The average particle size of γ′ phase as a function of time follows a cubic growth law of LSEM theory under the elastic interaction. Elastic stress can decelerate the coarsening process of γ′ phase.
Key word: Ni-Al alloys, Precipitation, Phase-field, Microstructure, Coarsening
目 次
1 绪论 1
1.1 研究背景及意义 . 1
1.2 相场法组织模拟 . 1
1.3 镍基高温合金的强化机理 . 2
1.4 本文研究内容 ... 3
2 相场模型 4
2.1 相场模型的理论基础 . 4
2.2 模型法基本原理 . 6
2.3 Ni-Al 合金相场模型的建立 8
2.3.1 相场控制方程 . 8
2.3.2 方程的数值解 11
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