摘要：作为一种具有高比强度和比刚度的轻质金属材料，镁合金因其质量轻、比强度高，在汽车工业中的应用越来越广泛，因此如何安全使用镁合金己受到人们的普遍关注。疲劳是各种工程构件服役期间的主要失效形式之一，对于镁合金结构件亦不例外，同时，镁合金由于其独特的密排六方的晶粒结构在性能上具有明显的各向异性。因此，研究镁合金的疲劳变形和断裂行为不仅具有理论意义，同时也具有一定的实用价值。本文对AZ31镁合金在循环应力作用下其低周疲劳力学行为的影响进行了研究，初步了解了镁合金疲劳裂纹扩展的各向异性。并用光学显微镜和电子显微镜观察试样的疲劳断口组织及表面形貌特征。   67166

 实验结果表明：①在相同的总应力、应变幅下，ED试样的疲劳裂纹扩展速率较大，疲劳寿命较短；②ED试样的屈服强度高于TD；③镁合金适用于Pairs公式；

毕业论文关键词：AZ31，镁合金，低周疲劳，各向异性

毕业设计说明书（论文）外文摘要

Title   The anisotropy of fatigue crack propagation of AZ31magnesium alloy                                                      

Abstract As a kind of high strength and light metal material stiffness，because of light weight, high strength，Therefore, how to safely use the magnesium alloy has received the widespread attention of people.Fatigue is a main failure form of engineering components in service period,For the magnesium alloy structural parts is no exception,at the same time,Magnesium alloy has the unique structure of close-packed six party structure,has obvious anisotropy,therefore,Fatigue deformation and fracture behavior of magnesium alloy has not only theoretical significance, but also has a certain practical value.This article studied AZ31 in the cyclic strain low cycle fatigue loads,and Anisotropy of fatigue crack extension of the magnesium alloy,Observation of fatigue fracture tissue samples and surface morphology by optical microscopy and electron microscopy.

The experimental results show that:At the same stress and strain conditions;The fatigue crack propagation rate of ET samples,the fatigue life is short;The yield strength of ED samples of more than TD specimens;Magnesium alloy is applicable for the Paris equation.

Keywords:  AZ31, magnesium alloy, low-cycle fatigue, anisotropy

目   录

1  绪论 1

1.1  引言 1

1.2  镁及镁合金 1

1.3  镁合金的研究现状 2

1.4  镁合金的组织及性能 2

1.5  变形镁合金 3

1.5.1  概述 3

1.5.2  变形镁合金的力学性能 3

1.6  镁合金的疲劳 3

1.6.1  疲劳概述 3

1.6.2  金属疲劳过程以及机制 6

1.7  镁合金的各向异性 7

1.7.1  各向异性