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摘要镍基高温合金是高温合金中应用最广、高温强度最高的一类合金，其中镍铝高温合金具有很好的耐腐蚀、耐磨损和耐气蚀性能，展示出了极好的应用前景。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。
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本文运用相场方法、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Ginzburg-Landau方程和Cahn-Hilliard相场方程进行数值求解，利用Matlab7.0进行编程，研究了体扩散下扩散系数对Ni-Al合金沉淀过程中γ′ 相微观形貌、平均粒径、粗化动力学、成分的影响规律。
结果表明，在形核阶段，随着扩散速率的增加，γ′ 相形核所需的孕育时间减小，形核率减小、形核数量减少。随着时效的进行，γ′ 相相邻颗粒相互连接，发生合并，聚集在一起形成较大的颗粒。该阶段相分解的驱动力为过饱和度的减小。在粗化阶段，大颗粒通过吸收临近的小的颗粒而长大，发生Ostwald熟化。该阶段相分解的驱动力为析出相界面能的减小。粗化速率随着扩散速率的增加而变大。γ′ 相平衡时刻的平均半径随着扩散速率的增加而变大。19256
关键词 Ni-Al合金，相场，微观组织，粗化，扩散系数
毕业设计说明书（论文）外文摘要
Title The effects of Ni-Al alloy precipitation in the bulk-diffusion
Abstract
Nickel based superalloy is the most widely used highest high temperature strength alloys. Ni-Al superalloy shows excellent application prospect because of its good resistance to corrosion and wear and cavitation performance. The main factors that influence the nickel base alloy performance are the organizational form,size,volume fraction and spatial distribution of the strengthening phase of superalloy. Thus, the study on the microstructure and coarsening can be particularly important for improving the performance of the Ni-Al superalloy .
In this article, we use the phase field method, the periodic boundary condition and the semi implicit fourier algorithm to calculate the Ginzburg-Landau equation and Cahn-Hilliard phase equation, and programming by using Matlab 7.0. We research the law of γ′ phase′ s micro morphology, average particle size, the coarsening kinetics, composition
under the effect of bulk-diffusion’s diffusivity.
The result indicate that at nucleation stage, when diffusivity increase , the incubation time of γ′ decrease, nucleation rate and nucleation number reduce as well. With the time going, adjacent particles connect with each other, start to merge and accumulate into a large one. In this stage, the power of phase decomposition is the decrease of supersaturation. At coarsening stage, larger particles get bigger by absorb nearby small ones and have Ostwald Ripening. At this stage, the decrease of interfacial energy of precipitated phase is the power of phase decomposition.Coaring rate increase with the raise of diffusion rate. The average radius of γ′ at equilibrium moment increase with the raise of diffusion rate as well.
Keywords Ni-Al alloys, Phase-field, Microstructure, Coarsening, Diffusivity
目 次
摘 要 I
Abstract II
1 引言 1
1.1 沉淀相形貌 1
1.2 第二相强化机制 2
1.3 计算机模拟 4
1.3.1 计算机在材料中的应用 4
1.3.2 相场模拟 4
1.3.2.1 相场模拟的基本原理 5
1.3.2.2 相场模拟的基本方程 5