Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： Lanthanum nitrate conversion coating was prepared on a hot-dip Galfan steel by dipping in a passivation solution of La(NO3)3. The surface morphology, chemical composition and structure of the coating were characterized by scanning electron microscopy (SEM) with X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The corrosion resistance of the conversion film coated steel was assessed by neutral salt spray tests (NSS), electrochemical polarization curve and electrochemical impedance spectroscopy (EIS). The results showed that the conversion coating was not uniform, which had grown preferentially on grain- and phase-boundaries as well as other active sites. The thickness of the coating increased, while cracks in the coating expanded gradually with the increasing dipping- time. The coating spall off after dipping for more than 30 min, and therewith the protective performance of the coating degraded. In comparison with the blank Galfan steel, the corrosion rate of the conversion film coated Galfan steel lowered down significantly.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： With the development of electronic products towards further miniaturization, multifunction and high- reliability, the packaging density has been increasing and the dimension of solder joints has been scaling down. In electronic packaging, during the soldering process of Sn/Cu system, an intermetallic compound (IMC) layer is formed at the interface between the molten solder and pad (substrate), the interfacial microstructure plays an important role in the reliability of solder interconnects. Generally, during the reflow soldering and subsequent aging process, a large number of Kirkendall voids may form at the Cu/Cu3Sn interface and in the Cu3Sn layer. The existence of Kirkendall voids may increase the potential for brittle interfacial fracture of solder interconnects and reduce the thermal conductivity. Thus, characterization of formation and growth of Kirkendall voids is very important for the evaluation of performance and reliability of solder interconnects. In this work, the formation and growth of Kirkendall voids at the Cu/Cu3Sn interface and in the Cu3Sn layer of Sn/Cu solder system have been investigated by means of phase field crystal modeling. The growth mechanism of Kirkendall voids was analyzed. The effects of thickness of Cu3Sn layer and impurity particles in the Cu3Sn layer on the growth of Kirkendall voids were discussed. Phase field simulation results show that the growth of Kirkendall voids exhibits four stages during the thermal aging, including the formation of atomic mismatch areas at the Cu/Cu3Sn interface, the rapid growth of the atomic mismatch areas leading to the formation of Kirkendall voids, the growth of Kirkendall voids and the subsequent coalescence of Kirkendall voids. Kirkendall voids nucleate preferentially at the Cu/Cu3Sn interface and their sizes increase with the aging time, and the coalescence of the voids can be observed obviously in the later stage of thermal aging. It has also been shown that the increase of the Cu3Sn layer thickness and the amount of impurity particles lead to an increase in both number and size of Kirkendall voids, as well as an increased growth exponent; and the number of Kirkendall voids increases initially and then decreases with the aging time.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：在450 ℃镀锌条件下，锌浴中加入质量分数为0.2%的Al，采用扫描电镜（SEM）观察镀层的结构特征，利用能谱仪（EDS）定量分析相的微区成分以及利用其线扫描和面扫描定性分析镀层截面元素变化情况。借助Miedema模型和Toop模型，计算了镀层中各二元Fe-Al、Fe-Zn和三元Fe2Al5Znx（η）金属间化合物（IMC）的热力学值，分析了随镀锌时间的延长，出现Fe2Al5抑制层失稳破坏而产生Fe-Zn反应的根本原因。结果表明，因为Fe-Al IMC比Fe-Zn IMC具有更稳定的热力学性质，钢基体与锌浴界面优先产生连续的Fe2Al5金属间化合物抑制层，抑制Fe-Zn反应，但随镀锌时间的延长，Fe2Al5的失稳破坏丧失对Fe-Zn反应的抑制作用，生成FeZn10（δ）相。 Fe2Al5抑制层的失稳机制有两种：一种是Fe2Al5/锌浴界面处Al的局部贫化导致Zn对Fe2Al5的侵蚀，形成Fe2Al5Znx，造成系统热力学稳定性降低，从而导致Fe2Al5被Zn侵蚀分解，同时在Fe2Al5∕锌浴界面产生FeZn10（δ）相；另一种是Zn通过Fe2Al5晶界向钢基体扩散，直接在Fe2Al5∕钢基体界面产生δ相，并引起Fe2Al5的迸发失稳。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：简述了外场辅助球磨技术的发展及其在材料制备中的应用。介绍了近年来发展的介质阻挡放电等离子体辅助球磨（DBDP-milling）新技术的基本原理和方法，阐述了DBDP球磨利用等离子体的热效应、高能电子轰击效应和球磨机械力效应的协同作用，增强粉体在球磨过程中的组织细化、活性激活、化学反应等效果和机理。在此基础上，简要介绍了该方法在硬质合金、锂离子电池负极材料、储氢材料等制备中的应用。研究结果表明，采用等离子体辅助球磨制备上述材料，不仅极大提高了球磨方法制备材料的效率，而且通过形成独特的结构显著提高了材料的性能；此外，还有可能建立新的材料生产制备工艺。已取得的研究成果表明，等离子体辅助球磨技术在粉末材料细化、材料表面改性、机械合金化、复合材料制备和气固反应等方面具有巨大的潜力。
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