摘要镁合金作为一种轻质的工程结构材料，在航空航天、国防军工、汽车、电子通讯等领域具有极其重要的应用价值和广阔的应用前景，是继钢铁和铝合金之后发展起来的第三类金属结构材料。但镁合金力学性能、塑性较差、拉断强度和疲劳强度也比铝低，使其应用范围受到很大限制。本次实验探索出变面轧制工艺，即多次转动样品，改变轧制面，制备超细晶镁合金，观察超细晶镁合金样品的织构和微观组织形貌，并将样品在应变控制模式下进行疲劳试验，得到滞后环曲线和疲劳曲线并分析。了解多面轧制对镁合金微观组织、力学性能和疲劳性能的影响。

实验结果表明：①经8道次变面轧制的AZ31，晶粒小至9.6µm，其屈服强度和抗拉强度也达到270MPa和310MPa，实现了AZ31合金的组织细化和力学性能的改善。②经8道次变面轧制的AZ31，疲劳循环周次也由8000多增至18146。67167

毕业论文关键词：超细晶 镁合金 变面轧制 疲劳性能

毕业设计说明书（论文）外文摘要

Title  Research on the low-cycle fatigue behavior of ultrafine-grained AZ31 magnesium alloy

Abstract：

Magnesium alloy is the lightest metal structure material, in recent years，it has been gradually applied to aerospace, national defense war industry, automobile, electronic communications and other fields. But the mechanical properties of magnesium alloy is poor, tensile strength and fatigue strength than aluminum is low, making it a very limited range of applications.This experiment explored polyhedral rolling technology to preparation the ultrafine-grain AZ31 magnesium alloy, and observed its microstructure morphology.The sample of the fatigue test is carried out under the strain control pattern, hysteresis loop curves and fatigue curve and analysis. Develop a better understanding of the mechanical properties and microstructural stability of ultrafine-grain AZ31 magnesium alloy

Experimental results indicates that:① The result of this study is to develop a better understanding of the mechanical properties and microstructural stability of ultrafine-grain AZ31 magnesium alloy made by polyhedral rolling technology.After eight times more surface rolling AZ31, small grain size 9.6μm, the yield strength and tensile strength of 270MPa and reached 310MPa.②The fatigue property of AZ31 has significantly increased.The fatigue cycle number is also increased to 18,146 .

Keywords：ultrafine crystalline ，magnesium alloy , polyhedral rolling , fatigue performance 

目 录

1绪论 1

1.1前言 1

1.2 AZ31 镁合金的组织及性能 1

1.3 AZ31 镁合金的晶粒细化 2

1.4 变形镁合金的变形机制及疲劳 3

1.5 本课题的研究背景及意义 6

2 实验方案与实验内容 7

2.1 实验方案思路 7

2.2 实验内容 7

2.3 断口金相组织观察 10

2.4 断口扫描电镜（SEM）分析 10

3 实验结果与分析 11

  3.1变面循环轧制工艺 11

  3.2 静态力学性能 12

  3.3 低周疲劳行为 13

  3.4 断口形貌观察结果及分析