Effect of Al/Mn ratio on corrosion behavior of lean Mg-Zn-Ca-Al-Mn alloy processed by twin-roll casting

• Published in: Corrosion science Vol. 212; p. 110938
• Main Authors: Wang, Bing-Yu, Li, Mei-Xuan, Li, Yi-Jia, Wang, Yu-Fei, Gao, Yipeng, Wang, Hui-Yuan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2023
• Subjects: A. Alloy; A. intermetallics; A. Magnesium; C. passive films; C. Pitting corrosion; A. Magnesium; C. passive films; A. Alloy; C. Pitting corrosion; A. intermetallics
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2022.110938

Adopting twin-roll casting (TRC) technique, lean Mg-1.2Zn-0.3Ca-0.3Al-xMn (x = 0.25, 0.38, 0.5 wt%) alloys with different Al/Mn ratio were prepared. The stoichiometric ratio of Al8Mn5 is taken as dividing line. Under Al/Mn>1.6, rhombohedral Al8Mn5 is formed, while under Al/Mn≤1.6, cubic β-Mn is generated. Because of lower Volta potential of Al8Mn5 than β-Mn, the alloy with Al/Mn>1.6 shows the lowest average corrosion rate (4.55 mm y−1). The formation of fine rather than coarse Al8Mn5 weakens micro-galvanic corrosion and relieves stress concentration, thus simultaneously endowing the alloy (Al/Mn>1.6) with admirable corrosion resistance and mechanical properties (UTS:∼266 MPa, YS:∼193 MPa, EF:∼20 %). [Display omitted] •Effect of Al/Mn atomic ratio on corrosion behavior of Mg-Zn-Ca-Al-Mn alloy is studied.•Rhombohedral Al8Mn5 is formed (Al/Mn>1.6), while cubic β-Mn is formed (Al/Mn≤1.6).•Fine Al-Mn phase are obtained by twin-roll casting and multi-pass rolling.•β-Mn is nobler than Al8Mn5 and larger Al/Mn ratio leads to less film breakdown.•Alloy with Al/Mn> 1.6 shows good corrosion resistance and mechanical property synergy.