Corrosion properties of magnesium alloys with various microstructure by severe plastic deformation

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14836
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Structural/Functional materials
• Research Institution: Doshisha University
• Principal Investigator: YUASA Motohiro 同志社大学, 理工学部, 准教授 (70635309)
• Research Collaborator: MIYAMOTO Hiroyki ; FURUKAWA Ryo ; MAJIMA Masasige ; MAULIDI Muhammad Lutfi ; SARR Mouhamadou Moustapha
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: マグネシウム合金 / 腐食 / 強ひずみ加工

Outline of Final Research Achievements

Corrosion resistance of ZK60 alloy and pure Mg processed by equal channel angular pressing (ECAP) was investigated using immersion tests in 5 wt% NaCl aqueous solution. The corrosion rates of ECAPed ZK60 alloys increased by increasing number of ECAP passes. Potentiodynamic polarization curves suggested that cathodic reaction was activated, and a passive film formed during immersion tests was weakened by increasing ECAP passes. This can be due to increasing intermetallic compounds and dislocation density during ECAP process. After heat treatment at 623 K for 1.5 h, the corrosion rates were significantly reduced by the heat treatment.
In contrast, the corrosion rate of pure Mg decreased after 1 pass ECAP and gradually increased after 2 pass ECAP. The grain size of ECAPed pure Mg was smaller than that of no-ECAPed pure Mg. Increasing the pass number, the grain size increased. After heat treatment, the corrosion rates increased. This can be due to the grain growth by heat treatment.

Free Research Field

金属材料学

Academic Significance and Societal Importance of the Research Achievements

マグネシウム合金は、輸送機器用の軽量材料として高いポテンシャルを有している一方で、腐食しやすいことが問題となっている。本研究では、強ひずみ加工により、マグネシウム合金の組織を制御することにより、その耐食性を組織の観点から制御できる可能性を見出した。強度や加工性といった機械的性質と耐食性をバランスできる加工技術へと展開でき、輸送機器の軽量化による安心安全社会と低炭素社会の実現へとつなげたい。