2018 Fiscal Year Annual Research Report
Characterization of deformation microstructure of Mg alloys containing LPSO structure via transmission electron microscopy
| Project/Area Number |
17F17732
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| Research Institution | Kyushu University |
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Principal Investigator |
陳 強 九州大学, 工学研究院, 教授 (30264451)
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| Co-Investigator(Kenkyū-buntansha) |
SHAO XIAO-HONG 九州大学, 工学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2017-10-13 – 2020-03-31
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| Keywords | Fatigue mechanism / Characterization / Magnesium alloy / LPSO structure |
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| Outline of Annual Research Achievements |
Magnesium alloys containing long period stacking ordered (LPSO) structure have attracted considerable attention recently due to their excellent mechanical strength and high-temperature properties. One of the important aspects to be as a potential structural material, the fatigue damage mechanisms of Mg-LPSO alloys should be understood, including the fatigue crack initiation mechanisms and crack propagation mechanisms. However, there’s little information about the fatigue mechanisms for Mg-LPSO alloys so far.
Our recent experimental results demonstrated that LPSO structures and solute atoms significantly influence the twin propagation, and plastic deformation induced redistribution and segregation of solute atoms along deformation interfaces during uniaxial compression. This suggests that the LPSO structures and solute atoms in the matrix determines the deformation behavior of Mg-LPSO alloys, which are also expected to affect their fatigue damage behavior.
Meanwhile, we detected fatigue crack along slip bands, LPSO-matrix interface, and grain boundary during ultrahigh fatigue test. That is, the severe strain localization should be closely linked to the LPSO phase and dislocations. The clarification of dominated crack initiation and propagation mechanism would shed new light on improving fatigue damage resistance of the magnesium alloys via designing microstructure.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
1. Twin boundaries are deflected by LPSO structures and solute atoms during compression.
2. Solute atoms segregation along deformation-induced interfaces is detected in Mg-LPSO alloys.
3. The fatigue behavior of Mg-LPSO alloys was characterized after ultrahigh cycle fatigue via FIB and TEM, and fatigue accumulative damage was detected near the LPSO-Mg matrix interfaces, which will be further analyzed in the near future.
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| Strategy for Future Research Activity |
1. In order to understand the fatigue behavior and corresponding mechanism of Mg-LPSO alloy, we will clarify the probable crack nucleation sites and investigate the possible crack evolution mechanisms via OM, SEM and TEM. Slip band, LPSO-Mg interface, grain boundary, and twin boundary would be focused on.
2. To highlight the effect of LPSO phases on fatigue behavior of Mg alloys, we will further systematically investigate the fatigue mechanism (nucleation and propagation) during different deformation process, including low cycle fatigue, high cycle fatigue, and ultrahigh cycle fatigue, for Mg-LPSO alloy.
3. Possible solute atoms redistribution during fatigue test would be expected due to the cyclic load, which will be elucidated based on the microstructural characterization.
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