Fatigue Behavior and Fracture Mechanism of High Strength Ultralight Mg alloys with LPSO Phase

• Project/Area Number: 16K06775
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Kyushu University
• Principal Investigator: CHEN QIANG 九州大学, 工学研究院, 教授 (30264451)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000); Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2017: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2016: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
• Keywords: 疲労 / マグネシウム合金 / き裂発生 / き裂伝ぱ / LPSO相 / 破壊 / 高サイクル / Ultrasonic Fatigue / Very High Cycle Fatigue / Magnesium Alloy / LPSO Phase / Crack Initiation / Crack Propagation / Fracture / Microstructure / き裂 / 微小き裂 / LPSO / 超高サイクル

Outline of Final Research Achievements

Ultrasonic fatigue testing was carried out on a rare earth-containing Mg alloy (Mg-Gd-Y-Zr) to investigate its small crack initiation and propagation. Most of fatigue life in the Mg alloys was consumed in nucleating and propagating small cracks. Fatigue cracks initiated along slip bands and EBSD analysis revealed that basal slipping was the predominant deformation.
On the other hand, atomic deformation and fracture mechanism involved were investigated, including the structural and chemical evolution in Mg-LPSO alloys after plastic deformation. Static plastic deformation induced kink boundaries and associated atomic segregation in Mg-Zn-Y alloys. Solute atoms segregated along deformation-induced interfaces in Mg-LPSO alloys. The fatigue crack site was detected to be along basal plane, other than twin boundary observed in single-phase Mg-RE alloy.

Academic Significance and Societal Importance of the Research Achievements

本研究は、溶質原子濃度変調と結晶構造変調が同期した、新奇な長周期積層構造（Long-Period Stacking Ordered: LPSO）を強化相とする軽量高強度マグネシウム合金の超高サイクル疲労破壊機構の解明が目的であり、LPSO型Mg合金の疲労信頼性の飛躍的な向上に貢献できるだけではなく、LPSO型Mg二相合金の強化機構の解明と疲労に強い超高強度LPSO型Mg合金の開発に繋がる。

Research Products

• [Int'l Joint Research] Shanghai Jiao Tong University/Sichuan Univesity/Chinese Academy of Sciences(中国)
• [Int'l Joint Research] 四川大学(中国)
• [Journal Article] Small crack initiation and early propagation in an as-extruded Mg-10Gd-3Y-0.5Zr alloy in high cycle fatigue regime (2019)
  • Author(s): He Chao、Shao Xiaohong、Yuan Shucheng、Peng Liming、Wu Yujuan、Wang Qingyuan、Chen Qiang
  • Journal Title: Materials Science and Engineering: A Volume: 744 Pages: 716-723
  • DOI: 10.1016/j.msea.2018.10.015
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Segregation of solute atoms along deformation-induced boundaries in an Mg-Zn-Y alloy containing long period stacking ordered phase (2019)
  • Author(s): Shao X.H.、Jin Q.Q.、Zhou Y.T.、Yang H.J.、Zheng S.J.、Zhang B.、Chen Q.、Ma X.L.
  • Journal Title: Materialia Volume: 6 Pages: 100287-100287
  • DOI: 10.1016/j.mtla.2019.100287
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Unravelling the local ring-like atomic pattern of twin boundary in an Mg-Zn-Y alloy (2018)
  • Author(s): Shao X. H.、Peng Z. Z.、Jin Q. Q.、Zhou Y. T.、Zhang B.、Zheng S. J.、Chen Q.、Ma X. L.
  • Journal Title: Philosophical Magazine Volume: 99 Issue: 3 Pages: 306-317
  • DOI: 10.1080/14786435.2018.1539262
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Very-high-cycle fatigue crack initiation and propagation behaviours of magnesium alloy ZK60 (2017)
  • Author(s): He Chao、Liu Yongjie、Li Jiukai、Yang Kun、Wang Qingyuan、Chen Qiang
  • Journal Title: Materials Science and Technology Volume: 34 Issue: 6 Pages: 639-647
  • DOI: 10.1080/02670836.2017.1407556
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Very High Cycle Fatigue Crack Initiation Mechanism in Nugget Zone of AA 7075 Friction Stir Welded Joint (2017)
  • Author(s): He Chao、Kitamura Kazuhiro、Yang Kun、Liu Yong-jie、Wang Qing-yuan、Chen Qiang
  • Journal Title: Advances in Materials Science and Engineering Volume: 2017 Pages: 1-10
  • DOI: 10.1155/2017/7189369
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Deformation-induced redistribution of solute atoms in an Mg-Zn-Y alloy (2018)
  • Author(s): Xiaohong Shao, Qiang Chen, Zhen-Zhen Peng, Kazuhiro Kitamura, Xiu-Liang Ma
  • Organizer: THERMEC’ 2018
  • Int'l Joint Research / Invited
• [Presentation] Small crack behavior of extruded Mg-Gd-Y-Zr alloy under high cycle fatigue (2018)
  • Author(s): Chao HE, Xiaohong SHAO, Yoshihiro FUKUSHIMA, Kaneaki TSUZAKI, Qingyuan WANG, Ning SU, Xiangwen HENG, Qian ZHAO, Liming PENGc, Yujuan WU, Qiang CHEN
  • Organizer: 日本機械学会 九州支部 第71期 総会・講演会
• [Presentation] Atomic-scale characterization of segregations at symmetrical kink boundaries in an Mg-Zn-Y alloy (2017)
  • Author(s): Xiaohong Shao, Qiang Chen, Xiuliang Ma
  • Organizer: The 6th International Conference on Magnesium
  • Int'l Joint Research
• [Presentation] 溶接継手の超高サイクル疲労強度と破壊機構 (2017)
  • Author(s): 何 超、王 清遠、陳 強
  • Organizer: JSME九州支部第70期総会・講演会
  • Place of Presentation: 佐賀大学理工学部（佐賀市）