非晶态结构及微组元与金属玻璃腐蚀行为的关联性研究

IMR OpenIR

	非晶态结构及微组元与金属玻璃腐蚀行为的关联性研究
	王子明
学位类型	博士
导师	卢柯 ; 王建强
	2010
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	金属玻璃腐蚀机理少量元素非晶态结构
摘要	"金属玻璃被誉为继钢铁和塑料后材料领域的第三次革命，随着该类材料工程化应用的推进，对腐蚀问题的关注显得尤为重要。金属玻璃具有单相均匀的结构特征及成分设计的灵活可控性,这些为深入认识腐蚀问题提供了全新的视角。目前,少量元素添加是强玻璃形成能力体系的一个重要特征，但其对腐蚀行为的影响尚不清楚；另外，非晶态结构自身对腐蚀行为的作用机制等也值得关注。本论文选取几种典型的金属玻璃模型体系，澄清了非晶态结构自身对腐蚀的作用机制并系统地研究了少量元素添加对金属玻璃选择性溶解和表面钝化膜稳定性的影响，揭示了与金属玻璃结构和成分相关的腐蚀行为的一些本征特性。本研究对合金腐蚀基本问题的理解、高耐蚀金属玻璃体系的设计有重要的指导意义。主要研究结果总结如下：（1）依据Ni50Nb50金属玻璃多晶型晶化的特点，首次澄清了非晶态结构自身特性对腐蚀行为的作用机制。研究发现非晶态结构能够抑制纳米尺度蚀点的萌生，该特性源于与材料结构密切相关的钝化膜/金属界面缺陷。同时，对亚稳蚀点的统计分析表明，非晶态结构可以有效促进初期蚀点的再钝化，而蚀点的进一步长大则主要依赖于合金成分。（2）详细研究少量Y元素添加对Fe基块体金属玻璃腐蚀行为的影响，确定了钝化膜稳定性与其半导体特性的关联性，并阐述了钝化膜的半导体掺杂效应。Fe基金属玻璃表面钝化膜为双层膜结构，外层膜为高价（Mo6+和Cr6+）离子组成，决定膜的过钝化溶解，内层膜为高度掺杂的Fe的氧化物，控制膜的半导体特性；Y3+离子通过对内层膜的半导体掺杂实现对外层膜稳定性的控制。该工作为设计或控制金属玻璃耐蚀性能提供了一条新的途径。（3）突破了合金选择性溶解的传统观念，在CuZr(Al)体系金属玻璃中通过少量元素（如Ni）添加实现了合金组元溶解倾向的反转，并证实了局域化学键合在合金溶解中的决定性作用。在此基础上，提出了局域原子相互作用模型，定量地理解了少量元素添加对金属玻璃溶解的作用机制，即Ni原子的引入改变了其周围Cu和Zr原子的化学作用环境，使得不同团簇内Cu与Zr原子溶解倾向发生改变，最终表现为电化学行为和表面形貌的巨大差异。"
其他摘要	"Metallic glass is recognized as the third revolution of engineering materials after the discovery of iron and plastic materials. As the attractive attentions paid on applications of metallic glasses, corrosion-related issues must be considered in advance. Further, the characteristics of homogeneity as well as the unique structure and compositional design of metallic glasses present us new opportunities to understand the intrinsic corrosion mechanisms. It has been noted that minor alloying is an effective approach for designing the glassy alloys. However, the role of minor alloying in corrosion is less certain. Also, the question concerning the effect of amorphous structure itself on corrosion behavior is highly needed to be clarified. In this thesis, several model metallic glasses were selected to clarify how amorphous structure impacts corrosion, and to elucidate the role of minor alloying elements in influencing the selective dissolution behavior and the stability of passive film, from which some intrinsic corrosion characteristics of metallic glass associated with amorphous structure and alloying were revealed. The present study would advance the understanding of metallic corrosion and guide the design of high corrosion-resistant alloys as well as promote the potential applications of metallic glasses. The main results are summarized as follows: (1) A model metallic glass, Ni50Nb50, which would undergo a polymorphous transformation during devitrification，was selected to clarify the correlation of amorphous structure with corrosion. It was firstly found that the pit initiation is inhibited greatly on amorphous sample relative to the crystallized one. The origin is thought to be related to the defective interface beneath passive film that inhibits the formation of pitting precursors in corrosion. Statistical analysis on the metastable pits suggests that amorphous structure can repassivate corrosion pits at an earlier stage, however, further growth of pits is relevant to the compositional effects. (2) The stability of passive films on Fe-based bulk metallic glasses was very sensitive to minor yttrium addition. Such effects are argued to be associated with the variations of semiconductor properties of passive film (i.e. defects concentration and band structure of passive film), induced by minor yttrium doping. It was shown that there exhibits a bi-layer structure of passive film on Fe-based bulk metallic glasses. The outer layer with high valence cations is responsible for the transpassive dissolution behavior of passive film, whereas the inner layer with doped oxides connects with the semiconductor properties. This result presents us an important hint that the corrosion resistance of amorphous alloys can be improved by elaborately tailoring the defect structure of passive film via the proper additions of minor alloying elements. (3) The dissolution selectivity of alloying components in CuZr-based metallic glasses can be switched by minor alloying of third elements, such as Ni. A local atomic interaction model was proposed to quantitatively explain the minor-alloying-switched susceptibility to dissolve. With such atomic interactions control, the more reactive components decline to dissolve but enrich on the surface, compelling the nobler components to dissolve away. This also leads to remarkable changes in electrochemical responses and surface corroded morphologies. The results expose an insight into the thermodynamic nature of alloy dissolution, i.e. a competition between local atomic interaction and electrochemical activity, emerging a new guidance for corrosion control."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64180
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	王子明. 非晶态结构及微组元与金属玻璃腐蚀行为的关联性研究[D]. 北京. 中国科学院金属研究所,2010.