Abstract

In this study, a systematic investigation on the effect of both aging temperature (250 °C and 330 °C) and time (chosen based on aging curves) on the distribution and volume fraction of the Mg₁₇Al₁₂ precipitates and subsequently on the corrosion behavior of the AZ80 magnesium alloy was carried out by conducting both immersion and dynamic polarization test in a freely aerated 3.5% NaCl solution. The analysis of corrosion products using Raman spectroscopy and X-ray diffraction and investigation of corrosion morphologies using scanning electron microscopy suggested galvanic corrosion of the anodic α-Mg matrix in contact with the cathodic Mg₁₇Al₁₂ precipitates. The higher corrosion resistance of the alloy aged at lower temperature (250 °C) was attributed to the higher number density of the Mg₁₇Al₁₂ precipitates than that at higher temperature (330 °C). In the peak aged condition, the average number densities of precipitates (1/µm²) were measured to be ~ 0.74 and ~ 0.32 and average corrosion rates (mm/y) were measured to be ~ 3.0 and ~ 5.0 at the aging temperatures of 250 °C and 330 °C, respectively. At a particular aging temperature, the corrosion resistance increased to a maximum at peak-aged condition followed by a decline in the over-aged condition and further increase with prolong aging, which was correlated with the number density, size and distribution of the Mg₁₇Al₁₂ precipitates.

Graphic Abstract

中文翻译：

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析出特性对AZ80镁合金腐蚀行为的影响

摘要

在这项研究中，系统地研究了时效温度（250°C和330°C）和时间（根据时效曲线选择）对Mg ₁₇ Al ₁₂析出物的分布和体积分数以及随后对腐蚀的影响AZ80镁合金的行为是通过在自由充气的3.5％NaCl溶液中进行浸没和动态极化测试来进行的。使用拉曼光谱和X射线衍射对腐蚀产物进行分析以及使用扫描电子显微镜对腐蚀形态进行研究表明，与阴极Mg ₁₇ Al ₁₂接触的阳极α-Mg基体的电化腐蚀沉淀。在较低温度（250℃）下时效的合金具有较高的耐腐蚀性，这是由于与较高温度（330℃）相比，Mg ₁₇ Al ₁₂析出物的数量密度较高。在峰值时效条件下，在20°C时效温度下，析出物的平均密度（1 / µm ²）为〜0.74和〜0.32，平均腐蚀速率（mm / y）为〜3.0和〜5.0。分别为250°C和330°C。在特定的时效温度下，耐腐蚀性能在峰值时效条件下达到最大值，然后在过时效条件下下降，并随着时效时间的延长而进一步提高，这与Mg ₁₇的数量密度，尺寸和分布有关铝_12个沉淀物。

图形摘要