论文总字数：19453字

摘 要

镁合金不仅是最轻质的金属结构材料，同时还具有储量丰富易回收、高阻尼、电磁屏蔽能力强、生物相容性好等诸多优点，因此广泛应用于航空航天、工业制造、军工生产、生物医疗等领域。其中稀土型镁合金以优异的高强度和高温抗蠕变性引起广泛重视，并在稀土对镁合金的强化机制进行了较为深入的研究，但仍不十分明确。元素扩散与合金中的相变、固溶等物理过程密不可分，因此研究元素在镁合金中不同条件下的扩散行为对镁合金的基础研究具有重要意义。

为此本课题利用扩散偶法设计制备了多组镁钪纯二元扩散偶，并设计不同扩散条件，以研究镁钪之间的扩散行为，并取得以下实验结论和进一步的研究设想。

⑴利用电子探针（EPMA）获取了773K、823K和873K条件下的多相扩散元素浓度分布曲线，得到较宽的β_bcc相扩散层。

⑵计算得到β_bcc相不同温度下的生长常数k：773K为6.34×10^-14、823K为44.81×10^-14、873K为189.83×10^-14，且生长常数与温度符合指数关系。

⑶计算得到β_bcc相中的互扩散系数数量级在10^-13~10^-12之间，其对数形式的数值随Sc增加而降低，且呈线性关系。

⑷基于麦克劳林展开外推Mg、Sc两种元素在β_bcc相中的杂质扩散系数，结果与温度均符合Arrhenius关系。

关键词：镁钪合金 多相扩散 扩散系数

ABSTRACT

Magnesium alloy is not only the lightest metal structure material, but also has many advantages, such as rich reserves, easy recovery, high damping, strong electromagnetic shielding ability, good biocompatibility, etc., so it is widely used in aerospace, industrial manufacturing, military production, biomedical and other fields. Among them, rare earth type magnesium alloy has attracted extensive attention due to its excellent high strength and high temperature creep resistance, and the strengthening mechanism of rare earth type magnesium alloy has been studied in depth, but it is still unclear. The diffusion of elements is closely related to the physical processes such as phase transformation and solid solution.

In order to study the diffusion behavior between Mg and SC, different diffusion conditions were designed, and the following experimental conclusions and further research ideas were obtained.

（1）The concentration distribution curves of multiphase diffused elements under 773K, 823K and 873K conditions were obtained by means of EPMA, and a wider phase diffused layer of pv _bcc was obtained.

（2）The growth constant k was calculated as follows: 773K was 6.34×10-14; 823K was 44.81×10-14; 873K was 189.83×10-14; and the growth constant was in an exponential relationship with the temperature.

（3）It is calculated that the order of magnitude of the mutual diffusion coefficient in the pv _bcc phase is between 10-13 and 10-12, and the value of its logarithmic form decreases with the increase of Sc, and the relationship is linear.

（4）Based on McLaughlin extrapolation Mg, Sc, the impurity in the two kinds of elements in the β_bcc phase diffusion coefficient, the results conform to the Arrhenius relationship with temperature

KEYWORD：Magnesium scandium alloy、Multiphase diffusion、Diffusion coefficient

目 录

摘 要 Ⅰ

ABSTRACT Ⅱ

第一章 绪 论 1

1.1选题背景 1

1.2镁及镁合金简介 1

1.3稀土镁合金研究现状 2

1.4扩散理论概述 3

1.4.1扩散基本理论 4

1.4.2扩散系数简介 4

1.4.3互扩散系数计算方法 5

1.4.4杂质扩散系数计算方法 7

1.5 Mg-RE多相扩散研究现状^[13] 7

1.6课题研究意义及主要内容 9

第二章 实验部分 10

2.1 实验材料与设备 10

2.2研究路线及实验方案设计 10

2.3样品制备及流程 12

2.4样品表征 15

2.4.1扫描电镜（SEM）显微组织表征 15

2.4.2 电子探针（EPMA）测定成分浓度分布曲线 15

第三章 前期结果分析与讨论 16

3.1 多相扩散浓度分布曲线 16

3.2 β_bcc相扩散系数测定 18

第四章 结论与展望 21

4.1结论 21

4.2展望 21

参考文献 22

第一章 绪 论

1.1选题背景

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