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

2018 Fiscal Year Final Research Report

• 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
• 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

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.

Free Research Field

構造・機能材料

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。