Tribocorrosion readily removes the protective corrosion product, creates new reactive corrosion sites and thus accelerates material loss in metallic materials. This is evidenced by a pronounced or gradual decline in open circuit potential (OCP) during tribocorrosion assessments. Here we report that grain refinement can not only enhance wear resistance in dry conditions, but also induce an anomalously stable OCP variation and fortify tribocorrosion resistance in ultrahigh-purity magnesium during tribocorrosion. The tribocorrosion tests revealed that the fine-grained Mg (FG-Mg) sample exhibited a wear rate (4.56 × 10−4 mm3/(N m)) approximately half that of the coarse-grained Mg (CG-Mg) sample (7.87 × 10−4 mm3/(N m)). CG-Mg showed a gradual OCP decrease, associated with a thin, unprotective tribocorrosion layer, even thinner than that resulting from dry sliding. Conversely, FG-Mg exhibited stable OCP evolution and quasi-linear tribocorrosion kinetics over time, attributed to a thick, protective tribocorrosion layer. Transmission electron microscopy data suggest that high-diffusivity pathways for oxygen along grain boundaries at the early tribocorrosion stages facilitate the formation of a continuous, protective MgO layer and an adjacent oxidized layer with a depth-dependent oxygen content gradient, enhancing tribocorrosion resistance in FG-Mg. Our findings offer valuable insights for strategically tailoring tribocorrosion resistance by modulating the OCP variation of highly active metals and alloys.

中文翻译：

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晶粒尺寸对超高纯镁摩擦腐蚀动力学的影响


摩擦腐蚀很容易去除保护性腐蚀产物，产生新的反应性腐蚀位点，从而加速金属材料中的材料损失。在摩擦腐蚀评估期间，开路电位 （OCP） 明显或逐渐下降证明了这一点。在这里，我们报道了晶粒细化不仅可以增强干燥条件下的耐磨性，还可以诱导异常稳定的 OCP 变化，并在摩擦腐蚀过程中增强超高纯镁的抗摩擦腐蚀能力。摩擦腐蚀测试表明，细晶粒 Mg （FG-Mg） 样品表现出磨损率 （4.56 × 10−4 mm3/（N m）），大约是粗晶 Mg （CG-Mg） 样品 （7.87 × 10−4 mm3/（N m）） 的一半。CG-Mg 显示 OCP 逐渐降低，这与薄的、无保护性的摩擦腐蚀层有关，甚至比干滑产生的更薄。相反，FG-Mg 表现出稳定的 OCP 演变和随时间推移的准线性摩擦腐蚀动力学，这归因于厚的保护性摩擦腐蚀层。透射电子显微镜数据表明，在早期摩擦腐蚀阶段，氧沿晶界的高扩散率途径有助于形成连续的保护性 MgO 层和相邻的氧化层，其氧含量梯度与深度有关，增强了 FG-Mg 的抗摩擦腐蚀能力。我们的研究结果为通过调节高活性金属和合金的 OCP 变化来战略性地定制抗摩擦腐蚀能力提供了宝贵的见解。