Search for novel highly corrosion-resistant Mg-Al-X alloy by suppressing Al-rich alpha phase

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K04774
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26050:Material processing and microstructure control-related
• Research Institution: University of Toyama
• Principal Investigator: Hatakeyama Masahiko 富山大学, 学術研究部都市デザイン学系, 准教授 (30375109)
• Co-Investigator(Kenkyū-buntansha): 砂田 聡 富山大学, 学術研究部都市デザイン学系, 特別研究教授 (00206575) ; 佐藤 紘一 鹿児島大学, 理工学域工学系, 教授 (30378971)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: マグネシウム合金 / 腐食特性 / 防食技術 / 電気化学

Outline of Final Research Achievements

Electrochemical measurements were performed on the Mg-Al alloy with the Al concentration systematically changed from 1 to 43 wt%. When the Al concentration is 1 to 8 wt%, the corrosion potential increases as the Al concentration increases, however the corrosion potential decreases from 9 wt%. In addition, the β-phase single-phase (43wt% Al) shows a potential of about -1.4V, which is about the same as 5wt% Al. Since this change in corrosion potential cannot be explained by simple purification by Al concentration, it is said that the difference in the thickness of the magnesium hydroxide film Mg (OH) 2 formed on the surface of each phase has an effect. Conceivable. (X = Zn, Ag) was found as an element that destabilizes the β phase of the Mg-Al-X alloy, and a large number of stabilizing elements (X = Sn, Bi, etc.) were obtained.

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

Mg合金は卑な金属で耐食性が悪く、Alを添加した合金として用いられる。Alを添加することで合金は貴にシフトし、耐食性は向上するものの、Al濃度の高い金属間化合物であるβ-Mg17Al12相や母相であるα相のなかにAl濃度が高い領域（Al-rich-α相）が形成し、それらが耐食性を劣化する。
β相を不安定化する添加元素を探索し、β相の析出を抑え、α相中のAl濃度を高く維持することで耐食性を向上する方法や、β相の析出を逆に促進し、β相の周囲に形成し、腐食の起点となるAl-rich-α相の形成を抑制する手法を開発した。この応用によりモバイル機器等に用いられるマグネシウム合金の寿命向上が期待される。