Choi Kwangmin, Shin Jaehyuck, Kang Heon
Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro Seodaemungu, Seoul 03722, Korea.
Materials Technology R&D Division, Korea Automotive Technology Institute (KATECH), 303 Pungse-ro Pungse-myeon, Cheonan-si 31214, Korea.
Materials (Basel). 2022 Feb 8;15(3):1259. doi: 10.3390/ma15031259.
To increase the utilization of die-cast Mg alloys with various shapes in a variety of environments, the corrosion behaviors of commercial die-cast Mg alloys with different thicknesses were investigated in neutral and alkali solutions at ambient temperature. A decrease in the thickness of a specimen leads to an increase in cooling and solidification rates, which, in turn, decreases the size of the eutectic β phases and the interphase distance, thus improving the hardness of the specimen. Specimens with relatively large β phases were more corroded under neutral conditions due to severe galvanic corrosion at the interface between α-Mg and the β phases, whereas they were protected by passivation films formed on the substrate in the alkaline solution. However, in the case of the alloy with thin thickness and high solidification rate, the fine β phases improved corrosion resistance by forming a net structure that acted as a barrier to corrosion propagation of the α matrix. These results suggest that the size and distribution of the eutectic phases should be appropriately controlled, depending on the environment.
为提高各种形状的压铸镁合金在多种环境中的利用率，研究了不同厚度的商用压铸镁合金在中性和碱性溶液中、室温下的腐蚀行为。试样厚度减小会导致冷却和凝固速率增加，进而减小共晶β相的尺寸和相间距离，从而提高试样的硬度。β相相对较大的试样在中性条件下腐蚀更严重，这是由于α-Mg与β相界面处的严重电偶腐蚀，而在碱性溶液中，它们受到在基体上形成的钝化膜的保护。然而，对于厚度薄且凝固速率高的合金，细小的β相通过形成网状结构提高了耐腐蚀性，该网状结构起到了阻碍α基体腐蚀扩展的作用。这些结果表明，应根据环境适当控制共晶相的尺寸和分布。
