Novel Corrosion Control of Mg Alloys in Structural Lightweight Multi-Materials Assemblies

通过使用坚固的轻质材料来减少运输车辆的总质量，可以说是提高燃料效率并从而减少有害排放的最佳手段。具有高比强度、高硬度和温成型性的锻造锌(锌-锆-稀土)镁合金为实现这一目标提供了作为轻质多材料结构组件组成部分的机会。阻碍镁合金成分广泛应用的一个关键技术问题是在水环境中的高溶解(腐蚀)速度。这在很大程度上是由镁(工业工程金属中最低的标准还原电位)固有的反应性、主导阴极过程的高析氢反应以及自然氧化物表面膜破裂的趋势所驱动的，并被厚度大得多且保护性差得多的腐蚀产物膜所取代。我的研究计划的长期目标是开发一个基本的知识库，使结构轻质多材料组件的制造成为可能，这些组件由新兴的先进材料和工艺(连接和表面处理)组成，具有更高的耐用性(腐蚀和疲劳)，从而刺激加拿大制造的独创性，以支持全球运输业。一个综合目标是提供一个包容性的多学科(电化学、表面科学和物理冶金)研究环境，教育和培训加拿大的下一代HQP，他们将推动开发和实施针对高强度轻质材料的创新腐蚀控制解决方案。在我最近的研究进展的基础上，下一个研究计划的里程碑是开发一个使能知识库，该知识库将支持ZE镁合金在轻型多材料组件中的成功部署，使用改进腐蚀控制的新方法。具体的短期目标包括：(I)开发一种由Li2CO3转化涂层(前处理)组成的新型电涂层方案，该方案能够密封修复缺陷部位；(Ii)开发一种新型的重新填充摩擦搅拌点焊连接技术，该技术机械地加入无毒的阴极动力学抑制剂来控制焊缝的腐蚀；以及(Iii)展示通过结合这两项创新而实现的更好的腐蚀控制：强大的轻质涂层ZE镁合金接头，具有与涂层铝合金相似的腐蚀控制程度。本研究计划将对三名HQP进行教育和培训：两名博士生和一名MASC级学生。

Reducing the overall mass of transportation vehicles by the use of strong lightweight materials is arguably the best enabling means to improve fuel efficiency and, thus reduce harmful emissions. Wrought ZE (Zn-Zr-rare earth) Mg alloys with high specific strength, stiffness and warm formability provide enabling opportunities as an integral part of lightweight multi-material structural assemblies to achieve this goal. One key technical issue preventing widespread implementation of Mg alloy components is the high rate of dissolution (corrosion) in aqueous environments. This is driven in large part by the inherent reactivity of Mg (lowest standard reduction potential among industrial engineering metals), the high rate of the hydrogen evolution reaction that dominates the cathodic process and the tendency of the native oxide surface film to breakdown and be replaced with a significantly thicker and much less protective corrosion product film. The long-term goal of my research program is to develop a fundamental knowledge base that enables fabrication of structural lightweight multi-materials assemblies comprised of emerging advanced materials and processes (joining and surface treatment) with improved durability (corrosion and fatigue) that spurs a made-in-Canadian ingenuity to support the global transportation industry. An integrated goal is to provide an inclusive multi-disciplinary (electrochemistry, surface science and physical metallurgy) research habitat that will educate and train Canada's next generation HQP whom will drive development and implementation of innovative corrosion control solutions for strong lightweight materials. Building upon my recent research progress, the next research program milestone is to develop an enabling knowledge base that will underpin successful deployment of ZE Mg alloy in lightweight multi-material assemblies using novel approaches for improved corrosion control. Specific short-term goals include: (i) develop a novel electro-coat coating scheme comprised of a Li2CO3 conversion coating (pre-treatment) that is capable of seal-healing defects sites, (ii) develop a novel refill friction stir spot welding joining technology that mechanically incorporates a non-toxic cathode kinetics inhibitor to control corrosion of the weld and (iii) demonstrate the improved corrosion control achieved through combination of the two proposed innovations: strong lightweight coated ZE Mg alloy joints with a similar extent of corrosion control exhibited by coated Al alloys. Three HQP will be educated and trained in this research proposal: two PhD level students and one MASc level student.