镁合金论文

I AZ91粉末状镁合金的氢化处理

及组织演变

摘 要

镁合金是目前最轻的金属结构材料具有比强度高、比刚度高、耐腐蚀、切削加工性能好、易于回收利用等一系列的优点，因而有着极其重要的应用价值与广阔的应用前景。但是，现有镁合金常温下的塑性变形能力和塑性加工性能仍然较低，限制了其应用。因此，提高各类镁合金的强度，改善其塑性，是拓展镁合金应用领域推动镁合金发展的关键。通过细化晶粒制备纳米晶镁合金，能够提高现有各类镁合金材料的强度和塑性，是发展镁合金的有效途径。

当镁合金粉末经氢化—歧化—脱氢—重组工艺处理后，粉末的微观组织被大幅度细化到纳米级。进一步研究发现，当粉末经脱氢重组后，其晶粒虽有所长大，但仍可保持在纳米级，这一过程被称为HDDR处理。本文主要研究粉末状镁合金的氢化过程及温度、氢压对氢化过程的影响。

本研究选择应用广泛的AZ91镁合金。采用“镁合金氩气中磨制成粉末→氢化处理→真空脱氢→组织性能分析测试”的工艺路线，来研究粉末状镁合金的氢化脱氢过程，对其微观结构，相组成的变化进行研究。利用X射线衍射(XRD)和扫描电子显微镜（SEM）对镁中MgH2的体积分数和表面形貌的变化进行分析。 II 由于实验仪器出了故障，本次试验需先将仪器修理完善。

关键词：AZ91镁合金，HDDR处理，氢化反应，晶粒细化，纳米晶材料

III HYDROGEN PROCESSING AND MICROSTRUCTURE

EVOLUTION OF AZ91 MAGNESIUM ALLOY

ABSTRACT

Magnesium alloys is the lightest metallic structural material. Due to the

unique properties, such as high specific strength and rigidity, easy to recycle

and so on, they have great potential for structural applications. However,

because of the plastic deformability of magnesium alloys is quite poor at

room-temperature, which is an intrinsic drawback to limit their applications. So,

enhancing the strength and deformability of magnesium alloy is the key to

expand their applications and promote the development of magnesium alloy

industry. Grain refinement is the effectual way to enhancing the strength and

deformability of Mg alloy.

When the magnesium alloy material was treated by hydrogenation-

disproportionation-dehydrogenation-restructuring process, the microstructure of

the material has been substantially refined to the nanoscale. Further studies

shows that the material has been treated by dehydrogenation and restructuring

process, its grains would grow up, but still remained at the nanoscale, which is

called HDDR processing. The paper mainly studies how the surface of block

magnesium alloy is hydrogenated and how the temperature and hydrogen IV pressure effect to the hydrogenation.

In this study, AZ91 has been used, which is currently the most popular

magnesium alloy. We study the hydrogenation and dehydrogenation process of

the block magnesium alloys, its microstructure, phase composition and surface

morphology by “magnesium alloy ingotslices polishing–hydrogenated–vacuum

dehydrogenation–organizations performance analysis test” process. The volume

fraction of MgH2 in Mg and changes of the surface topography were analyzed

using X-ray diffraction and scanning electronmicroscopy analysis, respectively.

KEY WORDS: AZ91 magnesium alloy, HDDR processing, hydrogenation,

grain refinement, nanocrystalline materials

V 目 录

第一章 绪 论 ......................................................................................................................... 1

1.1 引言 ............................................................................................................................. 1

1.2 镁及镁合金的概述 ..................................................................................................... 1

1.2.1 镁合金的优异性能 ........................................................................................... 3

1.3 镁合金的发展及应用 ................................................................................................. 4

1.3.1 镁合金的发展 ................................................................................................... 4

1.3.2 镁合金在国防、航空航天工业及汽车中的应用 ........................................... 5

1.4 镁合金材料的分类及研究状况 ................................................................................. 6

1.4.1 细晶镁合金的制备工艺及发展现状 ............................................................... 7

1.4.2 强应变塑性变形晶粒细化技术 ....................................................................... 8

1.4.3 快速凝固粉末冶金细晶工艺技术 ................................................................... 9

1.4.4 氢化处理细晶强化镁合金工艺技术 ............................................................. 10

1.5 本课题的目的及意义 ............................................................................................... 11

1.6 本文的研究内容 ....................................................................................................... 12

第二章 实验材料、设备及方法 ........................................................................................... 13

2.1 实验材料 ................................................................................................................... 13

2.2 实验主要设备 ........................................................................................................... 14

2.3 试样的制备 ............................................................................................................... 15

2.4 组织结构分析 ........................................................................................................... 15