Corrosion mechanism of Mg alloys involving elongated long-period stacking ordered phase and intragranular lamellar structure
Corrosion mechanism of Mg alloys involving elongated long-period stacking ordered phase and intragranular lamellar structure
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长周期堆垛有序相和晶内层状结构镁合金腐蚀机制
DOI：
10.1016/j.jmst.2023.01.005
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发表时间：
2023-02
影响因子：
10.9
通讯作者：
Ruizhi Wu
中科院分区：
文献类型：
--
作者：
Jinshu Xie;Jinghuai Zhang;Zhi Zhang;Zijian Yu;Zhihao Xu;Ru Wang;Daqing Fang;Xiaobo Zhang;Xiaoru Zhang;Ruizhi Wu
如何在保证镁合金强度的同时进一步提高镁合金的耐腐蚀性是一个长期的挑战。揭示电位波动对微电偶腐蚀及后续成膜的影响对于理解具有多强化相/结构的镁合金的腐蚀机理具有重要意义。在此，我们制备了高强度Mg-14.4Er-1.44Zn-0.3Zr（wt.%）含有混合结构的合金，即，拉长的长周期堆垛有序（LPSO）块+晶内堆垛层错（SF）/LPSO层错。具有细长LPSO块和晶内LPSO薄片的镁合金（EZ-500合金）获得良好的耐腐蚀性（2.2 mm y-1），而含有细长LPSO块和晶内SF的镁合金（EZ-400合金）显示出显著更高的腐蚀速率（6.9 mm y-1）。扫描Kelvin探针力显微镜（SKPFM）的结果表明，细长的LPSO块体作为阴极相（EZ-400合金为87 mV），SF作为弱阳极相（EZ-400合金为30 mV），导致EZ-400合金的电位波动较大。而EZ-500合金中的细长块体和晶内片层均为阴极LPSO相（67-69 mV），电位波动较小。准原位原子力显微镜（AFM）观察表明，高电位波动会引起强烈的微电偶腐蚀，导致腐蚀膜不能快速形成，最终形成疏松多孔的膜层;而相对较低的电位波动会使腐蚀模式更加均匀，有利于保护膜的快速形成。因此，我们提出通过控制电位波动形成“均匀电位”强化组织是开发高强度耐蚀镁合金的有效途径。
It is a long-term challenge to further improve the corrosion resistance while ensuring the strength of magnesium (Mg) alloys. Revealing the effect of potential fluctuation on the micro-galvanic corrosion and the subsequent film formation is important for understanding the corrosion mechanism of Mg alloys with multiple strengthening phases/structures. Here, we prepared the high-strength Mg-14.4Er-1.44Zn-0.3Zr (wt.%) alloys containing hybrid structures, i.e., elongated long-period stacking ordered (LPSO) blocks + intragranular stacking faults (SFs)/LPSO lamellae. The Mg alloy with elongated LPSO blocks and intragranular LPSO lamellae (EZ-500 alloy) obtains good corrosion resistance (2.2 mm y–1), while the Mg alloy containing elongated LPSO blocks and intragranular SFs (EZ-400 alloy) shows a significantly higher corrosion rate (6.9 mm y–1). The results of scanning Kelvin probe force microscopy (SKPFM) show the elongated LPSO blocks act as cathode phase (87 mV in EZ-400 alloy), and the SFs serve as the weak anode (30 mV in EZ-400 alloy), resulting in high potential fluctuation in EZ-400 alloy. On the contrary, both elongated blocks and intragranular lamellae are cathodic LPSO phase (67–69 mV) in EZ-500 alloy, leading to a lower potential fluctuation. Quasi in-situ atomic force microscope (AFM) observation indicates that high potential fluctuation would cause strong micro-galvanic corrosion, and subsequently leads to the failure in rapid formation of corrosion film, finally forming a loose and porous film, while relatively low potential fluctuation could result in more uniform corrosion mode and facilitate the rapid formation of protective film. Therefore, we propose that it is an effective way to develop high-strength corrosion-resistant Mg alloys by controlling the potential fluctuation to form a “uniform potential” strengthening microstructure.
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