纳米相的形成对铝基金属玻璃点蚀行为的影响

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	纳米相的形成对铝基金属玻璃点蚀行为的影响
	张锁德
学位类型	硕士
导师	王建强
	2011
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	合金铝金属玻璃极化点蚀钝化纳米晶体相
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。金属玻璃本质上是成分和结构均匀的单相合金，通常具有高的耐局部腐蚀能力。Al-TM-RE（TM =过渡族元素，RE=稀土元素）金属玻璃的耐点蚀能力远高于传统Al合金，因此该体系在作为表面非晶金属涂层方面有很大的应用前景。但是在非晶涂层的制备过程中，各种类型纳米晶体相的析出不可避免，这将大大降低涂层的耐蚀性能。因此，深入理解各种类型纳米晶体相的析出对Al基金属玻璃的点蚀行为的影响对于Al基金属玻璃作为耐蚀非晶涂层的应用非常重要。本论文选取典型的Al-TM-RE体系，通过调整合金成分和控制熔体急冷工艺参数，成功制备出非晶基体复合单一纳米晶体相α-Al、Al-TM和Al-RE的非晶-纳米晶合金（AN），详细研究了三种类型纳米晶体相的析出与Al基金属玻璃点蚀行为的内在联系。结论如下：（1）基于非晶结构形成的相选择理论，选取Al-Ni-Ce三元模型体系，成功制备出非晶基体分别复合单一纳米晶体相α-Al、Al3Ni和Al11Ce3的三种AN合金，相应的合金成分分别为Al88Ni8Ce4、Al83Ni13Ce4和Al83.5Ni9Ce7.5；同时通过改变熔体急冷参数也获得了相应的同成分完全非晶态合金（AM）。（2）对比研究了三种AN合金与相应的同成分AM合金在含氯离子（Clˉ）溶液中的电化学极化行为。纳米晶体相α-Al的析出没有使Al基金属玻璃的高耐点蚀能力变差。然而，纳米晶体相Al3Ni或Al11Ce3的析出则降低了Al基金属玻璃耐点蚀能力，AN(Al3Ni) 和AN(Al11Ce3)合金的点蚀电位与相应的同成分AM合金相比分别降低了48.8 mV和77.4 mV。三类纳米晶体相的析出致使Al基金属玻璃耐点蚀能力的降低程度大小依次为：α-Al ＜ Al3Ni ＜ Al11Ce3。纳米晶体相的析出对Al基金属玻璃点蚀行为的影响主要体现在蚀点萌生和蚀点早期长大阶段。（3）非晶态样品和晶态样品纯Al、Al3Ni及Al11Ce3的钝化膜厚度无明显差别而钝化膜的组成及其抵抗Clˉ的能力明显不同。非晶态样品的钝化膜含有很少量的Ni2+和Ce3+，纯Al样品的钝化膜只含有Al3+，它们的结构都比较均匀，在NaCl溶液中浸泡24小时的样品表面只有少量低结合能的吸附态的氯化物。但是Al3Ni和Al11Ce3样品钝化膜分别含有少量的Ni2+掺杂和大量的对Ce3+掺杂，钝化膜的均匀性和稳定性较差，Clˉ不仅大量吸附于钝化膜表面，而且渗透到钝化膜内部和钝化膜/基体界面，从而促进了蚀点的萌生。"
其他摘要	"Metallic glass is recognized as the third revolution of engineering materials after the discovery of iron and plastic materials. Metallic glass is intrinsically single phase alloys with homogeneous structure and components, which is expected to possess high resistance to localized corrosion. Al-TM-RE (TM: Transition Metal; RE: Rare Earth element) metallic glass has much higher resistance to pitting corrosion than that of traditional Al alloys, and therefore it is very promising for its applications as amorphous metallic coatings. However, the precipitation of nanocrystalline phases would occur unavoidably in the process of preparing the amorphous metallic coatings, which can deteriorate their corrosion resistance. Thus, identifying and understanding the role of varied types of nanocrystals in pitting corrosion is of great interest for the application of metallic glasses as amorphous metallic coatings. In this thesis, three types of amorphous-nanocrystalline alloys (AN) with a single nanocrystal (α-Al, Al-TM or Al-RE intermetallics) embedded in Al-TM-RE glassy matrix were obtained directly by melt quenching. The correlation of the three types of nanoscale precipitates with pitting corrosion of the Al-based metallic glasses has been studied. The conclusions were summarized as follows: 1. On the basis of the phase selection theory, three types of AN alloys, with a single nanocrystal α-Al、Al3Ni or Al11Ce3 precipitated in amorphous matrix, were obtained directly by melt quenching, and the corresponding alloy composition is Al88Ni8Ce4, Al83Ni13Ce and Al83.5Ni9Ce7.5 respectively. Fully amorphous alloys (AM) for each alloy composition were also obtained by controlling cooling rates during the quenching. 2. The pitting corrosion resistance of three types of AN alloys in chloride-containing solutions was investigated compared to their AM alloys. The high resistance of Al-based metallic glasses to pitting corrosion is not deteriorated by nanoscale α-Al precipitation. However, when nanoscale Al3Ni or Al11Ce3 intermetallics precipitated in the amorphous matrix, the good pitting corrosion resistance is markedly lost, and the Epit of AN(Al3Ni) and AN(Al11Ce3) alloys remarkably decreased with an average value of 48.8 mVSCE and 77.4 mVSCE to corresponding AM alloys respectively. The deterioration of pitting corrosion resistance for three types of nanocrystals is in the order α-Al < Al3Ni < Al11Ce3. The effects of the precipitated nanocrystals on the pitting corrosion behavior of Al-based metallic glass are mainly related to the pit initiation and its early growth stages. 3.There is no clear difference for the passive film thickness of both amorphous and crystalline alloys, but the components and the resistance to Cl− incorporation of the passive film are rather different. The passive film of AM alloy contains significantly-depleted Ni cations and Ce cations and the passive film of pure Al contains only cationic Al, thus they both are compositionally uniform. Only the adsorptive chloride species with a lower binding energy were detected on the surface of the these two samples after 24h-immersion in NaCl solution. However, the passive film contains a few Ni cations and is enriched in Ce cations for Al3Ni and Al11Ce3 samples respectively, therefore they are structurally nonuniform and instable. Chloride ions not only adsorb on the surface but also incorporate into the passive film and the oxide/metal interface, which facilitates the pit initiation."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64367
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	张锁德. 纳米相的形成对铝基金属玻璃点蚀行为的影响[D]. 北京. 中国科学院金属研究所,2011.