SiCp表面化学镀镍合金层的成分与形貌研究

SiCp因其高强度,高模量、耐热、耐磨等优良性能而被作为颗粒增强体制备金属基复合材料。采用优化后的SiCp表面化学镀镍工艺,获得了镍合金包覆SiCp,并对镀镍合金层进行了X－ray衍射成分分析以及镀覆层形貌的SEM考察。结果表明,镀覆层主要为部分非晶态的镍与镍磷合金以及Ni2P的化合物夹杂;粒子的分散很好,结团较少。     

Thermodynamic Analysis of In As Sb C H System and Design of MOVPE Process for In(As,Sb) Semiconductor

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镁合金AZ91表面化学镀镍层的制备及性能研究

为了优化镁合金表面化学镀镍工艺,降低施镀过程中的污染,研究了AZ91镁合金表面直接化学镀镍工艺,并应用SEM对镀层表面形貌进行观察,通过EDS及XRD对镀层成分及物相进行了分析,采用划线划格法、静态浸泡法分别对镀层与镁合金基体的结合力、镀层的防腐蚀性能进行了分析.研究结果表明:AZ91镁合金表面可通过直接化学镀镍获得结合力良好、表面硬度较高的镍镀层.镀层的成分分析显示:由于NaH2PO2发生自身氧化还原反应,镀层中存在少量P.在3.5%NaCl溶液中的静态腐蚀试验结果表明:镀层的耐腐蚀性能良好,对合金基体可以起到较好的防护作用.     

AZ91D镁合金化学镀镍前处理工艺及腐蚀行为研究

为了改进传统的镁合金化学镀镍前处理工艺和确定以硫酸镍为主盐的镁合金化学镀镍的最佳工艺.采用碱性焦磷酸盐进行浸蚀代替铬酸浸蚀,去除合金表面的油污和氧化物;然后用氢氟酸溶液进行活化.通过正交试验确定了化学镀镍的最佳工艺.结果表明:采用碱性焦磷酸盐浸蚀的前处理工艺、在最佳施镀条件下镀2h,镀层厚度达到20μm,与基体结合良好;镀层为Ni-P微晶,表面平整、致密,磷的质量分数达11.7%.在质量分数为3.5%的NaCl溶液中的动电位极化测试结果表明,镀层可对AZ91D镁合金起到良好的防护作用.     

In situ measurement of corrosion on the nanoscale

Measurement of the electrochemical properties phase-by-phase on the nanoscale in real (commercial) alloys is critical to understanding the microstructure-corrosion relationship and subsequently controlling it. This work presents a novel AFM based in situ corrosion probing methodology (for the first time) that is capable of resolving the electrochemical activity (impedance response) into the nanometer range; the method subsequently having major ramifications in the study of aluminium alloy corrosion, the interpretation of corrosion propagation, and the subsequent development of corrosion resistant aluminium alloys.     

In situ observations and crystallographic analysis of martensitic transformation in steel

The development of a martensitic structure in a low-carbon and low-alloy steel was characterized using in situ confocal laser microscopy, high-speed photography and crystallographic analysis, including the nature of variant selection. The initial stage of transformation involves the partitioning of the austenite grain into packets, after which the rate of transformation is gradual. The crystallographic orientation of the plates that form is not random, but involves selection determined by the relationship between the shape deformation direction and the free surface. The vicinity of austenite grain and twin boundaries, and martensite/austenite interfaces also affect variant selection.     

棒状共晶界面成分分布及对平界面生长的影响

用定向凝固法揭示了MnSb/Sb棒状共晶 (纤维复合材料 )平界面生长条件。基于成分过冷理论 ,推导了棒状共晶组元耦合扩散边界层内浓度梯度要求的GL/V条件。并从二元共晶界面不稳定性的类型和溶质分布形式的角度 ,分析了造成界面不稳定的原因和现有判据的局限性     

In situ electrochemical wet cell transmission electron microscopy characterization of solid-liquid interactions between Ni and aqueous NiCl2

Electrodeposition and electropolishing of nanograined nickel has been observed using an in situ electrochemical wet cell developed for transmission electron microscopy. The cell employs two thin film nickel electrodes in a 0.1 M aqueous NiCl₂ electrolyte, which were biased at ±1 V. Anisotropic electrodeposition was observed in which growth of the nickel film across the substrate occurred much more rapidly than growth perpendicular to the substrate. The anisotropic behavior results from relatively equiaxed nanograins nucleating at the growth front with little subsequent coarsening. Grains were observed to nucleate ahead of the growth front, suggesting a new mechanism for electrochemically driven growth across a substrate which depends on ionic surface adsorption ahead of the growth front. During electropolishing the dissolution of nickel tended to occur more isotropically. The film thinned relatively uniformly until certain regions displayed Rayleigh instabilities. At this point the film broke up and some regions coarsened rapidly and/or were subject to electromigration.     

In situ observation and thermodynamic calculation of MnS in 49MnVS3 non-quenched and tempered steel

Based on thermodynamics calculation, the results of the formation temperature of MnS inclusions of non-quenched and tempered steel during heating process were discussed. It is shown that while the solid fraction is 0.9, MnS inclusions began to precipitate in the final stage of solidification. The solidification process of 49MnVS3 non-quenched and tempered steel during heating has been observed in situ using a confocal scanning laser microscope (CSLM), which agrees well with the thermodynamics calculation. MnS particles were coarsening during heating process, which would reduce the pinning effect on the austenite grain boundaries and bring about the sudden growth of some austenite grains in this stage.     

Sensing, Control, and In Situ Measurement of Coating Properties: An Integrated Approach Toward Establishing Process-Property Correlations

Over the last decade there has been an explosion in terms of available tools for sensing the particle spray stream in thermal spray processes. This has led to considerable enhancement in our understanding of process reproducibility and reliability. Despite these advances, the linkage to coating properties has continued to be an enigma. This is partially due to the complex nature of the build-up process and the associated issues with measuring properties of these complex coatings. In this paper, we identify critical issues in processing-structure-property relations particularly with respect to the linkage to particle properties. Our goal is to demonstrate an integrated strategy, one that combines particle state sensing, with process mapping and extracting coating properties in situ through the development of robust and advanced curvature-based techniques. These techniques allow estimation of coating modulus, residual stress and, non-linear response of thermal sprayed ceramic coatings all within minutes of the deposition process. Finally, the integrated strategy examines the role of process maps for control of the spray stream as well as tailoring properties of thermal spray coatings. Examples of such studies for yttria-stabilized zirconia thermal barrier coatings are discussed.