摘要本文研究了挤压态稀土镁合金的低周疲劳性能，并且与常规的挤压态AZ31镁合金进行比较。通过观察GW102K和AZ31镁合金疲劳后的微观结构和表面形貌特征，发现GW102K镁合金含有大量的沉淀颗粒和相对较弱的织构，这使得其屈服不对称性增大。不同与AZ31镁合金，GW102K镁合金拥有近对称的应力-应变滞回线和边界循环硬化现象。这种对称性显著降低了在低周疲劳过程中的拉伸平均应力。由于存在小尺寸的反向塑性区，GW102K镁合金在疲劳裂纹扩展区断裂表面是粗糙的，GW102K镁合金的低周疲劳寿命要比被AZ31镁合金高。68042

毕业论文关键词  镁合金 织构 孪晶 疲劳 

毕业设计说明书（论文）外文摘要

Title  Low-cycle  fatigue  bahavior  of  extruded  GW102K   Magnesium  alloys                          

Abstract

The low-cycle fatigue properties of extruded Mg-10Gd-2Y-0.5Zr (GW102K) magnesium alloy have been studied and compared to those of conventional extruded AZ31 magnesium alloy. Typical post-fatigue microstructure and surface morphology features are presented for both the GW102Kand AZ31 alloy. It is found that GW102Kalloy contains a large amount of precipitated particles and possesses a relatively weak basal texture, which gives rise to near symmetric yield asymmetry. Different from AZ31 alloy, the GW102Kalloy shows near-symmetric stress-strain hysteresis loops and marginal cyclic hardening. This symmetry significantly reduces tensile mean stress during low-cycle fatigue process. Due to the small reversible plastic zone size, the GW102Kalloy shows rough faceted fracture surfaces in the fatigue crack propagation zone. Accordingly, the low-cycle fatigue life of GW102Kalloy is found to be longer than that of AZ31 alloy. 

Keywords  Magnesium alloys  Twinning  Texture  Fatigue

目  次

1 引言 1

1.1 镁合金塑性变形特征 2

1.2 镁合金塑性变形的机制 2

1.2.1 镁合金塑性变形的滑移机制 2

1.2.2 镁合金塑性变形的孪生机制 3

1.2.3 镁合金塑性变形的晶界滑动机制 3

1.3稀土镁合金的特点、应用及现状 4

1.3.1稀土在镁合金中的作用机理 4

1.3.2稀土镁合金的发展历史及应用现状 4

1.4 低周疲劳 5

2 实验方案与内容 7

2.1 实验方案思路 7

2.2实验内容 7

2.2.1实验材料与试样制备 7

2.2.2 静态力学实验 8

2.2.3 应变控制下的低周疲劳试验 8

2.3 断口金相组织观察 8

2.4 断口扫描电镜（SEM）分析 9

3 结果与讨论 10

3.1 显微组织与织构 10

3.2 力学性能 11

3.3 低周疲劳性能 12

3.4 断口形貌分析 14

结论