2016 Fiscal Year Annual Research Report
ＬＰＳＯ相を有する高強度Ｍｇ－Ｚｎ－Ｙ合金の超高サイクル疲労破壊機構の解明
| Project/Area Number |
16F16809
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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) |
HE CHAO 九州大学, 工学研究院, 外国人特別研究員
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| Project Period (FY) |
2016-11-07 – 2019-03-31
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| Keywords | Ultrasonic Fatigue / Magnesium Alloy / LPSO Phase / Crack Initiation / Crack Propagation / Very High Cycle Fatigue |
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| Outline of Annual Research Achievements |
Magnesium alloys containing long period stacking ordered (LPSO) structure received considerable concerns in the last decade due to their good combined properties of mechanical strength and corrosion resistance. This research work aims to investigate high cycle fatigue (HCF) and very high cycle fatigue (VHCF) behaviors of LPSO phase containing Mg alloys, including (1)HCF and VHCF strength of Mg alloys with LPSO phase; (2)cyclic deformation mechanisms of matrix Mg and LPSO phase; (3)fatigue crack initiation mechanisms and the effect of LPSO phase on the fatigue behaviors.
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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. Carried out pre-experiments on a commercial magnesium alloy (ZK60) using ultrasonic fatigue system.
2. Designed three different ultrasonic fatigue specimens for fatigue crack initiation, propagation and strength investigations, respectively.
3. Submitted a manuscript to the 70th General Meeting held by Japan Society of Mechanical Engineers Kyushu Branch and gave a presentation entitled "Very high cycle fatigue strength and failure mechanisms of welded joints" in Saga University.
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| Strategy for Future Research Activity |
1. Observation on the fatigue crack initiation process. Fatigue damage mechanism at a stress well below the bulk yield strength will be investigated in LPSO containing Mg alloys with different microstructures using scanning electron microscopy, electron back-scattering diffraction (EBSD) and transmission electron microscopy (TEM). Changes in surface microstructure at different stages of fatigue life will be measured with an in-situ optical microscope (OM) in order to determine the fatigue damage mechanisms that govern the cyclic deformation and fatigue failure.
2. The interaction between crack growth and microstructure. Using plate specimen with a small notch, the fatigue crack propagation rate and the effect of LPSO on the crack growth rate and crack path will be investigated.
3. VHCF strength and failure mechanism. Samples taken from the gauge sections of fatigued specimens as well as from materials unaffected by cyclic loading will be used for TEM investigation in order to characterize the morphology of basal dislocation arrangements. The deformation kink band and the deformation twin caused by cyclic loading will be discussed, and their effect on the fatigue crack initiation will be addressed.
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Research Products
(2 results)
