2004 Fiscal Year Final Research Report Summary
Development of High Strength Wrought Magnesium Alloy by Multidirectional Forging under Decreasing Temperature Conditions
| Project/Area Number |
15560623
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
YANG Xuyue The University of Electro-Communications, Faculty of Electro-Communications, Research Associate, 電気通信学部, 助手 (20293128)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAI Taku The University of Electro-Communications, Faculty of Electro-Communications, Professor, 電気通信学部, 教授 (40017364)
MIURA Hiromi The University of Electro-Communications, Faculty of Electro-Communications, Associate Professor, 電気通信学部, 助教授 (30219589)
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| Project Period (FY) |
2003 – 2004
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| Keywords | multi-directional forging(MDF) / fine grain / kink band / continuous dynamic recrystallization / texture / annealing / grain growth / Mg alloy AZ31 |
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| Research Abstract |
The research falls roughly into the following two heads.
(1)Strain-Induced Grain Refinement in Mg Alloy during Hot Forging
Grain refinement of a magnesium alloy AZ31 was studied in multi-directional forging(MDF) with decreasing temperature from 623K to 423K. The MDF was carried out up to cumulative strains of around 5 with changing the loading direction during decreasing temperature from pass to pass. The structural changes can be characterized by the evolution of many mutually crossing kink bands at low strains followed by increase in their number and misorientation, finally resulting in a fully developed fine-grains at high strains. MDF with decreasing temperature can accelerate the evolution of much finer grains and the improvement of plastic workability. An average grain size of 0.3 μm is formed at an accumulative strain of 4.8 and at 423K. It is concluded that grain refinement under MDF conditions occurs by a series of deformation-induced continuous reactions; that is essentially similar to continuous dynamic recrystallization(cDRX).
(2)Isochronal Annealing Behaviors of Mg Alloy After Hot Deformation
Temperature dependence of the average grain size (D)is categorized into three temperature regions, i.e. (a)incubation period of grain growth at<450 K, (b)rapid grain coarsening at 473-523 K, and (c)normal grain growth at T>550 K. The number of fine grains per unit area, however, is reduced remarkably even in region (a). It is concluded, therefore, that grain growth takes place continuously in the whole regions. While, deformation texture scarcely changes even after annealing at high temperatures. It is concluded that the annealing processes operating in the hot deformed magnesium alloy is mainly controlled by grain growth accompanied with recovery, that is continuous static recrystallization(cSRX).
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