镍铝高温合金强化相沉淀行为研究

摘要镍基高温合金具有优异的高温强度、韧性、抗疲劳性能、抗氧化和抗热腐蚀性能，被广泛应用于航空、航天等领域。镍铝高温合金强化相（γ′ 相）的组织形态、尺寸、体积分数和空间的分布状况是影响合金的强化程度主要因素。因此，对于γ′ 相的微观组织以及粗化行为的研究在提高镍铝高温合金性能方面有着重要作用。本文采用相场方法、周期性边界条件和半隐式傅里叶谱算法，在傅里叶空间中对相场方程方程和 Hilliard ahn Landau inzburg   C G进行数值求解，利用 Matlab7.0编程，研究了弹性应力下 Ni-Al 合金γ′ 相不同温度的沉淀过程的微观形貌演变，温度对 Ni-Al合金沉淀过程中γ′ 相成分、序参数、体积分数及其粗化行为的影响规律。随着时效温度的降低，γ′ 相的微观组织形貌由高温时的方块状转变为较低温时的长方块状分布，一方面有奥斯特瓦尔德（Ostward）熟化进行，另一方面块状的颗粒长大粗化并相互连接，γ′ 相的数量不断增多、粗化速率不断减小。另外，γ′ 相在粗化过程中，其颗粒尺寸的立方与时间成正比。弹性应力作用下，γ′ 相的粗化行为符合 LSEM理论，并且弹性应变会阻碍 γ′ 相的粗化过程。 59646
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

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 镍铝高温合金强化相沉淀行为研究:http://www.751com.cn/cailiao/lunwen_64927.html