Microstructural study of galvanized coatings formed in pure as well as commercial grade zinc baths

This investigation is an effort to have a better understanding of the growth kinetics and morphology of the coating formed during the galvanizing process in pure as well as commercial grade zinc baths. The protective coating that is formed during hot dip galvanizing, normally between 450 and 480°C, consists of a series of Fe-Zn intermetallic layers, which have been identified as gamma (Γ), delta (δ), zeta (ξ) and an outer eta (η) layer, highly rich in zinc. There is apparently no delay in the formation of ξ or δ phases in both pure as well as the commercial grade zinc baths. The gamma (Γ) phase is formed after an incubation time of about 30 s at a bath temperature of 470°C in the pure zinc bath. Its formation is further delayed in the commercial grade zinc bath. The last morphological feature is the formation of a second ξ layer at the ξ/δ interface in the pure zinc bath. In the commercial grade zinc bath two different morphologies of ξ phase are seen starting from the lowest dipping time, and also the overall coating is considerably thicker due to formation of several iron-zinc intermetallics which degrade its ductility and outward appearance. Commercial grade zinc also enhances the dross formation in the bath and deteriorates the quality of the coating. Presence of transverse cracks as well as entrapment of dross particles in the coating is attributed to the less compact coating that is formed in the commercial grade zinc bath.     

纯镁渗锌处理表面合金化机制研究

对纯镁进行了表面渗锌处理，研究了扩渗温度及扩渗时间对于合金化渗层组织、相结构及反应层连续性的影响。结果表明：扩渗温度的选择有一个合适的范围，温度过低，扩渗速度太慢甚至Zn元素原子的能量达不到其激活能，不能产生活性原子，扩渗过程无法进行。温度过高虽然有利于形成合金化渗层，但会使基体晶粒粗化，甚至改变整个基体，而且，温度过高不利于反应层（金属间化合物区）的稳定：扩渗时间的延长会促使Zn的进入量和金属间化合物的生成量增加，并削弱晶界扩散优势的影响，最终使固溶层和反应层趋于均匀化。要形成连续的反应层，扩渗温度应控制在400℃～420℃，相应的扩渗时间为8h以上。     

The kinetics of diffusion of hydrogen in niobium

The kinetics of hydrogen diffusion in niobium were studied in the temperature ranges of 200° to 300°C and 600° to 700°C by gas-metal absorption experiments. The hardness profile was correlated with the concentration of hydrogen on specimens of various grain sizes. It was found that the diffusion kinetics of both temperature ranges could be represented by a single Arrhenius-type rate equation. The activation energy and the preexponential factor were found to be 10.000±320 cal per mole, and 1.8±1.0×10⁻² cq cm per sec., respectively. No observable effect of grain size was found on the diffusivity.     

镍基高温合金液相扩散焊接头组织及性能

镍基高温合金GH4413在高温下具有较为优异的高温持久强度和抗蠕变性能,在航空发动机和各种工业燃气轮机中得到广泛应用。以BNi 2作为填充合金材料使用液相扩散焊对GH4413合金进行了连接,研究了在焊接温度分别为1 030和1 080 ℃、保温时间分别为30和60 min等不同焊接参数下GH4413镍基高温合金的接头微观组织、成分分布和显微硬度。扫描电镜(SEM)以及能谱分析结果表明,当焊接温度为1 080 ℃、保温时间为60 min 时,钎缝组织中形成了性能良好的固溶体,且随着焊接温度的升高和保温时间的延长,钎缝的宽度增加,钎料元素向母材中的扩散深度逐渐增加,在母材近缝区形成了金属间化合物。     

金属陶瓷复合塑料切粒刀的研制及应用

研究了ＴｉＣ－ＮｉＣｒ金属陶瓷在塑料切粒刀上的应用。这种切粒刀结构特点是金属陶瓷刀刃与钢刀体通过高温真空扩散焊复合为一体。结果表明这种金属陶瓷复合切粒刀性能比钢结硬质合金切粒刀更好。     

预扩散处理对原位生成TiC_p/Fe基粉末冶金复合材料组织与性能的影响

将水雾化Fe粉与Ni粉、Mo粉、Ti粉混合均匀,然后在800℃、50%H2+50%Ar(体积分数)气氛保护下进行预扩散处理,将预扩散粉与电解Cu粉和石墨粉混合,通过压制与烧结,制备Ti C颗粒增强Fe基复合材料。通过X射线衍射分析、扫描电镜及能谱分析和力学性能测试等手段,研究预扩散处理对原位生成Ti Cp/Fe基粉末冶金材料组织与性能的影响。结果表明:Fe-Ni-Mo-Ti混合粉在800℃下预扩散处理后形成表面粗糙的团球状预扩散粉末颗粒,但合金元素在Fe粉颗粒内分布不均匀。与用混合粉制成的Ti Cp/Fe基复合材料相比,用预扩散粉制备的材料孔隙率略有增加。随预扩散时间延长,材料中富Ti区的尺寸减小,组织明显细化,珠光体分布更均匀,同时形成大量弥散分布的粒径在0.1~0.5μm的Ti C颗粒。材料的硬度和抗弯强度都随原料粉预扩散时间延长而提高,用60 min预扩散粉制成的Ti Cp/Fe基复合材料的硬度HRB和抗弯强度分别达到63.6和613.7 MPa,比用混合粉制成的Ti Cp/Fe基复合材料分别提高11.8%和38.3%。用预扩散粉末制备的Fe基复合材料的断裂形式为具有一定韧性断裂特征的脆性断裂。     

Effect of technological factors on the diffusion kinetics in the copper-aluminum composite

An investigation is performed on the effect of thermal treatment conditions, furnace atmosphere, and technological protective coatings of various compositions on the formation of the phase composition of diffusion layers in welding zones of a layered intermetallic composite of the Cu-Al system produced by complex technology.     

MnS夹杂对钢中氢扩散行为的影响

通过实验和有限元计算研究了MnS夹杂对钢中氢扩散行为的影响.结果表明:当MnS夹杂长度取向与氢渗透方向平行时,氢在钢中的表观扩散系数随MnS含量的增加而增加;当MnS夹杂长度取向与氢渗透方向垂直时,氢在钢中的表观扩散系数随MnS含量的增加而降低.对于具有扩散通道效应和陷阱效应的第二相,它对氢扩散的影响取决于扩散通道效应和陷阱效应的强弱以及第二相的形状、数量和取向.     

The synergy between powder metallurgy processes and welding of metallic alloy: a review

ABSTRACT

Powder metallurgy (PM) technology is an ideal manufacturing process to produce near net shape parts i.e. part that requires little or no machining, examples of PM processes are spark plasma sintering, isostatic pressing and additive manufacturing. PM allows maximisation of materials and produces part with optimised mechanical and physical properties. Also, PM process provides the possibility to further increase the industrial use of PM parts by fabricating it into complex geometrical shapes via joining. Joining is the most important mechanical process necessary for PM parts to perform in actual service conditions expected in automobile parts and structural parts. Despite apparent advantages of PM processes, joining PM parts has been a tedious process, due to challenges associated with inherent characteristics, like porosity, chemical composition and impurities like oil or grease, which tend to impair the weldments property. In this document, a review of PM process is presented, focusing on different welding methods that can be used to effectively join PM components.     

The kinetics of atomic diffusion to stacking faults and the related special problems in cold-worked alpha brasses

The diffusion kinetics of solute atoms to the stacking fault layers were investigated by the Laplace transformation method in binary homogeneous alloys. The room temperature annealing kinetics of stacking faults in cold-worked alpha brasses, which were studied by an X-ray diffraction technique, were analyzed in terms of the present theoretical findings. The chemical diffusivities in cold-worked (filings) Cu−10Zn and Cu−22.7Zn alpha brasses were determined as equal to 1.7×10⁻²¹ and 1.5×10⁻¹⁹ cm²/s at room temperature (300 K), respectively. Finally, the concentration of athermal monovacancies was estimated in plastically deformed Cu−10Zn (the particle size 20 μm) and Cu−22.7Zn (the particle size 75 μm) alloys and was found to be about 2.0×10¹⁹ and 3.0×10¹⁹ cm⁻³, respectively.     

全身扩散加权成像在恶性淋巴瘤诊断与疗效评估中的价值

Objective:The aim was to evaluate the role of whole body diffusion weighted imaging (WB-DWI) of magnetic resonance in the diagnosis and efficacy evaluation of malignant lymphoma.Methods: The clinical manifestation of whole body diffusion weighted imaging of 47 patients with malignant lymphoma being pathologically proved were carried on by retrospective analysis and to compare with 10 healthy volunteers.There were 8 cases of Hodgkin's lymphoma (HD) patients, of which WB-DWI examination of 5 cases were carried out before and after treatment and 3 cases were done after treatment.There were 39 cases of non-Hodgkin's lymphoma (NHL) patients, of which WB-DWI examination in 19 cases were acted before treatment, 11 cases were done before and after treatment and 9 cases done after treatment.In apparent diffusion coefficient (ADC) diagram the ADC values of lymph nodes in patients with malignant lymphoma and healthy volunteers were measured respectively, among 16 patients the ADC values of parts of lymph node being consistent with the initial inspection were determined again and compared the values before and after, and compared with healthy volunteers.Results: Whole body magnetic resonance diffusion weighted imaging (MR-DWI) showed more sensitive to lymphoma, and 372 lymph nodes greater than 1 cm were detected with MR-DWI.Before treatment, mean ADC value of 35 patients with malignant lymphoma was (0.86 0.21) × 10-3 mm2/s, of which an average ADC values of 28 cases after treatment was (1.22 0.31)× 10-3 mm2/s, before and after treatment difference of the average ADC values of patients was statistically significant (P < 0.05); the average ADC value of cervical lymph nodes of 10 healthy volunteers (1.29 0.12) × 10-3mm2/s and of 30 patients with malignant lymphoma before treatment was statistically significant (P < 0.05), and to compare with 28 patients after treatment difference of the ADC values was not statistically significant (P > 0.05).Conclusion: WB-DWI and ADC values being measured in the clinical diagnosis of malignant lymphoma, staging and evaluation of efficacy of monitoring is a fast and effective technology, with some clinical value.     

Self-esteem and the diffusion of leadership style.

Neither simple imitation, nor motivational coincidence, is adequate either to explain the frequent, superficial absence of similarities in leadership style across hierarchical levels (leadership climate) or to prescribe the best means for changing the style involved when climate does occur. Self-esteem of the lower-level supervisor is investigated as a mediating variable in this problem, in the context of an organization in which no formal human relations training had taken place. Variables were measured by questionnaires submitted to 17 foremen and their 330 male subordinates in a packaging materials plant. Hypotheses, all confirmed by the data, relate supportiveness of the foreman's supervisor to the foreman's behavior toward his subordinates through the attendant consequences of the foreman's self-esteem. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

扩散方程解和烧结材料中合金元素的分布

讨论了扩散微分方程在几种条件下的积分解, 采用辛普生法计算误差函数erf（z）的定积分值, 就2个不同浓度无限源的扩散状况, 进行了数值计算. 描述了计算扩散分布的FORTRAN程序框图, 给出了C、Co、Cr、Mn、Mo、Ni及V等合金元素在Fe中扩散分布的计算结果, 在通常烧结温度1 120～1 150 ℃下, Mo和Ni等元素的扩散距离仅1～3μm. 因此, 若加入合金元素粉末, 其粉末粒度应控制于此值, 以保证扩散的均匀性, 同时还讨论了合金分布均匀性对机械性能的影响.     

碳化对混凝土中氯离子扩散的影响

混凝土与静浆快速碳化0,14,28d后浸泡到3.5%NaCl溶液中650d,测试了混凝土不同深度的自由氯离子、总氯离子含量,计算出混凝土的表观氯离子扩散系数和氯离子结合能力;采用压汞法测试了不同腐蚀制度下静浆表层的孔结构,利用DSC分析了静浆的腐蚀产物.结果表明:混凝土碳化后浸泡到腐蚀溶液中,增加了混凝土中的氯离子含量,提高了混凝土表观氯离子扩散系数,降低了混凝土对氯离子的结合能力;且随碳化时间的增加,变化幅度变大.快速碳化粗化了混凝土的孔结构,其大于30nm的毛细孔数量增加了11%,最可几孔径增加了17nm;降低了混凝土中Friedel'S生成量,以及混凝土对氯离子的化学结合能力.     

钢板中氢扩散的数值模拟

为了加强钢板生产过程中氢的控制,建立了钢板内部氢扩散的数学模型,分析了钢板芯部的氢质量分数与扩散系数、钢板的厚度、氢的初始质量分数和时间之间的关系。随着钢板的厚度增加,氢的扩散效果大幅度降低;随着钢板缓冷开始温度的降低,同一厚度钢板芯部氢的扩散效果也越来越差。采用高温堆垛缓冷或采用保温坑缓冷等工艺可实现高温扩氢,从而避免轧后钢板的氢致缺陷。