Corrosion Mechanisms in Amorphous Alloys: Critical Compositional and Structural Defects for Local Corrosion

技术：非晶态金属材料优异的局部耐腐蚀性和优异的钝化性能通常归因于消除了微观结构的不均一性。然而，缺乏对确切的管理关键缺陷的识别，存在相互矛盾的解释。无论是在传统的玻璃材料中，还是在较新的块体金属玻璃合金中，关于优异耐腐蚀性的根本来源的这个普遍问题仍然没有解决。只要机理尚不清楚，就无法预测部分玻璃化对腐蚀的影响。在这方面，有许多悬而未决的问题，存在着通过仔细选择模型合金来澄清这些问题的机会，这些模型合金能够拒绝或接受关于耐蚀性的每一种假设。对于临界缺陷尺寸，选定的非晶态合金可以通过初级晶化部分析出玻璃，以在剩余的富溶质非晶基质中形成孤立的富溶质和/或贫溶质晶体，作为模型材料，能够探索一系列不均匀。当非均匀度低于临界尺寸时，耐腐蚀性良好的机理将在补充的多学科研究中确定。本课程将探讨非晶态基质中细小非均匀相具有良好耐腐蚀性的几个可测试假设。关于将结构不均匀与成分不均匀的作用分开的必要性，有机会通过选择在成分不变的情况下发生脱玻璃化的合金来探讨这一问题。例如，某些Fe-B、Co-B、Cu-Zr和Al-Sm非晶态合金可以通过多晶态晶化来形成相同成分的晶态固溶体。此外，还将重点研究非晶相的结构和成分松弛在腐蚀溶解引起的纳米级粗化中的作用(S)。非技术性：更广泛的影响包括人力资源开发。CESE培训腐蚀、材料科学/工程和表面科学等多学科领域的学生，是向美国工业、政府和学术界提供具有腐蚀知识的材料专业人员的主要供应商。代表性不足的性别和族裔学生一直是并将继续是这项补助金综合培训和研究工作的重点。在弗吉尼亚大学，通过国家科学基金会资助的论文/学位活动的研究和外部出版、演示和知识创造/传播的双重作用，实现了研究和教育的整合。学生和PI在广泛的兴趣论文、专业论文、会议和K-12学生的实验室参观/演示中传播成果。

TECHNICAL: The outstanding local corrosion resistance and excellent passivity of amorphous metallic materials is often attributed to the elimination of microstructural heterogeneity. However, identification of the exact governing critical defect is lacking and competing explanations exist. In both traditional glass materials as well as newer bulk metallic glass alloys, this generic question concerning the fundamental origins of excellent corrosion resistance remain unresolved. As long as the mechanism is unclear, the impacts of partial devitrification on corrosion cannot be forecast. In this regard, there are a number of unresolved issues and he opportunity exists to clarify these issues through careful selection of model alloys that enable rejection or acceptance of each hypothesis for corrosion resistance. Regarding the critical flaw size, selected amorphous alloys can be partially devitrified by primary crystallization to form isolated solute rich and/or solute lean crystals in a remaining solute rich amorphous matrix which serve as model materials that enable exploration of a range of non-uniformities. The mechanism for good corrosion resistance when a non-uniformity is below the critical size will be determined in complimentary multidisciplinary studies. Several testable hypotheses for the good corrosion resistance of small nonuniformities in an amorphous matrix will be explored. Regarding the need to separate the roles of structural from compositional non-uniformities, the opportunity exists to explore this issue through selection of alloys which undergo devitrification without change in composition. For example, certain Fe- B, Co-B, Cu-Zr and Al-Sm amorphous alloys can devitrify by polymorphous crystallization to form crystalline solid solutions of the same composition. In addition, , origins of corrosion of the heat-treated amorphous matrix will be studied focusing on the role(s) of structural and compositional relaxation of the amorphous phase in nano-scale roughening by corrosive dissolution. NON-TECHNICAL: Broader implications include human resource development. The CESE trains students in the multidisciplinary area of corrosion, materials science/engineering and surface science and is a major supplier of materials professionals with corrosion knowledge to US industry, government and academia. Under represented gender and ethnic students have and will continue to be a focus of integrated training and research endeavor on this grant. Integration of research and education is accomplished at UVA through dual role of research from NSF supported activities in both theses/degrees and for external publication, presentation and knowledge creation/dissemination. Students, as well as the PI, disseminate results in broad interest papers, specialty papers, conferences, and lab tours/demos for K-12 students.