高铬白口铸铁复合孕育的作用及动力学效应

采用V 渣 Ti Zn对高铬白口铸铁进行复合孕育.在炉内、炉外实行"二步法"处理并按孕育合金异质形核的生核能大小设计分级处理的顺序,起到了控制碳化物的析出量和改善析出形态,净化铁液,净化晶界,细化晶粒等良好的孕育效果.这些变化主要是复合孕育所产生的动力学效应对其影响的结果.     

用于小型薄壁灰铸铁铸件的复合孕育方法

介绍了在中频炉熔炼及废钢+增碳剂+回炉料配料条件下,生产小型薄壁灰铸铁件的复合孕育方法.该孕育方法将SiSr孕育剂与SiFe复合使用,能有效确保A型石墨析出、改善断面组织的均匀性、减少白口倾向,因而既能强化孕育效果,又能降低生产成本.     

高铬白口铸铁复合变质的作用及动力学效应

采用Re-A l-B i-Mg对高铬白口铸铁进行复合变质。在炉内、炉外实行"二步法"处理并按变质合金异质形核的生核能大小设计分级处理的顺序,起到了控制碳化物的析出量和改善析出形态,净化铁液,净化晶界,细化晶粒等良好的变质效果。这些变化主要是复合变质所产生的动力学效应对其影响的结果。     

高铬白口铸铁复合变质的作用

采用RE-A1-Bi-Mg对高铬白口铸铁进行复合变质。在炉内、炉外实行“二步法”处理并按变质合金异质形核的生核能大小设计分级处理的顺序，起到了控制碳化物的析出量和改善析出形态，净化铁液，净化晶界，细化晶粒等良好的变质效果。这些变化主要是复合变质所产生的动力学效应对其影响的结果。这种变质作用受制于复合变质在冶金处理过程中所应具备的相关的动力学条件。     

高锰钢复合变质的作用及动力学条件

采用RE-Ca-Ti-Al对高锰钢进行复合变质.在炉内、炉外实行"二步法"处理并按变质合金异质形核的生核能大小设计分级处理的顺序,起到了控制碳化物的析出量和改善析出形态,净化钢液,净化晶界,细化晶粒等良好的变质效果.这些变化主要是复合变质所产生的动力学效应对其影响的结果.这种变质作用受制于复合变质在冶金处理过程中所应具备的相关的动力学条件.     

复合变质对低铬白口铸铁的作用

采用Re-Al-Bi—Mg对低铬白口铸铁进行复合变质。在炉内、炉外实行“二步法”处理并按变质合金异质形核的生核能大小设计分级处理的顺序,起到了控制碳化物的析出量和改善析出形态、净化铁液、净化晶界、细化晶粒等良好的变质效果。这些变化主要是复合变质所产生的动力学效应对其影响的结果。这种变质作用受制于复合变质在冶金处理过程中所应具备的相关的动力学条件。     

孕育与变质处理对高Ni-Cr铸铁的影响

研究了75SiFe孕育和REMg变质对金属型铸造高Ni-Cr铸铁铸态和回火态的组织与硬度的影响。结果表明,75SiFe孕育处理使石墨析出数量增多,增加了奥氏体+石墨的共晶体数量,石墨片长度增加,而板条状碳化物数量减少。REMg变质促进点球状石墨析出,石墨析出数量减少,碳化物转变为断网分布,即呈岛状和骨骼状,高冷却速度弱化REMg的变质作用。75SiFe孕育回火处理促进奥氏体分解,回火后残余奥氏体较多。75SiFe孕育降低高Ni-Cr铸铁的铸态和回火态硬度,而REMg变质可略提高高Ni-Cr铸铁的铸态和回火态硬度。     

固溶后冷却方式对Inconel X-750合金组织和性能的影响

采用SEM、TEM、EDAX和相分析等分析手段,研究Inconel X-750合金固溶后不同冷却方式下组织和性能的变化。结果显示:水冷和油冷抑制合金中γ′相的析出,时效后均析出球形的γ′相。炉冷后合金中析出一次立方体形γ′相和二次球形γ′相,时效后再次析出球形γ′相;水冷和油冷后晶界上无碳化物析出,时效后晶界上均析出细小针状M₂₃C₆。炉冷后合金晶界上析出块状M₂₃C₆,时效后碳化物尺寸略微长大,形状基本不变;炉冷+时效后合金的强度最高,水冷+时效后合金的冲击性能最好。     

高强灰铸铁孕育覆盖剂的研究

生产高强度灰铸铁一般要经孕育处理和加稻草灰覆盖操作.本文提出的孕育覆盖剂主要由孕育元素、助溶剂和覆盖材料三部分的碎粒混合组成.其处理工艺是一种把孕育处理和其他炉外处理技术——熔渣处理、过滤处理和铁水的覆盖保温工艺结合起来的综合炉外处理工艺.即在出铁槽上把一定量的孕育覆盖剂撒到流动的铁水上将孕育和覆盖两个处理工序一次完成.经孕育覆盖剂处理的机床铸铁件在生产中试用,证明具有如下效果;1.简化炉前操作,改善工作环境.2.孕育效果良好,并延长衰退时间.3.提高铁水流动性,并使铸造内应力显著降低.     

铸铁孕育不良缺陷的形成机制及防止措施

对高镍奥氏体球墨铸铁碎块状石墨和灰铁D型石墨的形态进行研究分析,认为铸铁孕育不良缺陷与凝固过程中奥氏体和石墨的析出时机有直接关系:当奥氏体大量析出,而石墨析出严重滞后,易形成异常组织;当石墨优先析出的倾向增大,则易形成正常组织。球墨铸铁孕育不良会使石墨析出严重滞后,奥氏体析出时机提前,从而形成碎块状石墨、spiking枝晶、反白口、白口等缺陷组织。在生产实践中,根据缺陷类型的不同,改变孕育量、孕育剂类型、孕育剂粒度、孕育方式、孕育温度或采用特殊孕育剂等强化孕育措施可有效防止缺陷的形成。     

Protective ability of cerium-containing conversion films on aluminium

The options for electroless deposition of conversion films of lanthanum group metal oxides, in particular cerium, as an alternative to chromate conversion films (containing Cr⁶⁺) have been studied on aluminium. The main task of the study was to establish the influence of copper ions as a component of electrolytes for conversion treatment on the processes of formation and on the corrosion protective ability of cerium oxide films.

It has been ascertained that the electrochemical activation of the aluminium surface in the presence of Cu²⁺ in the electrolyte, leads to formation of oxide layers richer in cerium and possessing a better protective ability.

The presence of active cathodic sections of electroless, contact-deposited Cu has been shown to promote the corrosion activity of the system, due to the possibility of the appearance of micro-galvanic couples Al/Cu. A model experiment has been carried out to establish the inclination of the system to pitting corrosion. It has been shown that at the studied concentration of Cu²⁺ in the electrolyte the character of the corrosion does not change observably but there is a catalysing effect of the copper ions in the working electrolyte. The copper islands on the Al surface also have a catalysing effect, which is dominating in the processes of cerium oxide film formation. The chemical state and the composition of the conversion films have been defined by XPS measurements.     

30CrMnSi钢过热组织超细化工艺对比研究

对30CrMnSi钢过热组织采用多种热处理工艺进行了超细化处理,运用定量金相分析技术对处理结果进行了对比和评价,并讨论了每种工艺的晶粒细化机制。结果表明：“两次正火＋淬火”工艺对该钢的过热组织超细化效果显著;当循环次数为2－3次时,“奥氏体单相循环淬火”工艺也有较好的效果。     

Influence of niobium additions on high-temperature-oxidation behavior of Ti3Al alloys and coatings

In this study, the oxidation properties of Ti₃Al+Nb bulk alloys, as well as IMI 829 alloy, coated with a Ti₃Al+Nb layer, have been considered. Model alloys have been prepared, with 5–25 at.% niobium contents; 50-m-thick Ti₃Al+10 at.% Nb coatings have also been deposited on IMI 829 by triode sputtering. Bulk alloys and coated substrates have been exposed to cyclic and isothermal oxidation in air between 700 and 800°C. Niobium additions generally caused the oxidation rate of Ti₃Al to decrease significantly. In all cases rutile is the main oxide formed. It is believed that the ability of niobium to dissolve in the rutile lattice, and therefore to lower the oxygen diffusion rate through the oxide layer, is a contribution to the observed oxidation resistance enhancement. The formation of niobium oxide has also been envisaged for this matter.     

Role of cadmium on corrosion resistance of Zn-Ni alloy coatings

Cadmium (Cd) catalyzed Zn-Ni alloy plating has been accomplished galvanostatically on mild steel (MS) using gelatin and glycerol as additives. The effect of addition of Cd into Zn-Ni bath has been examined in terms of nickel (Ni) content and corrosion resistance of Zn-Ni-Cd ternary alloy coatings. The process and product of electrolysis under different concentrations of additives and Cd have been investigated by cyclic voltammetry (CV). The effects of current density (c.d.) on Ni content of the alloy have been studied by spectrophotometric method, supported by EDX analysis. The deposition has been carried out under different concentrations of Cd ranging from 0.004 to 0.1 M. The corrosion rates (CR) of Zn-Ni alloy coatings have been found to decrease drastically with addition of Cd. It has been also revealed that the CR of binary Zn-Ni alloy coatings decreased with the increase of Cd concentration only up to a certain optimal concentration, i.e., up to 0.02 M, and then remained unchanged. An effort to change the anomalous type of codeposition into normal one by changing the molar ratios of the metal ions, i.e. [Cd²⁺]/[Ni²⁺] as 0.01, 0.05 and 0.25 has remained futile. CV study demonstrated an important role of Cd in mutual depositions of Zn²⁺ and Ni²⁺ ions by its preferential adsorption, thus leading to the increased Ni content of the alloy. The bath composition and operating parameters have been optimized for deposition of bright and uniform Zn-Ni-Cd alloy coatings. Changes in the surface morphology and phase structure of Zn-Ni alloy coatings due to addition of Cd has been confirmed by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) study respectively. Experimental investigations so as to identify the role of Cd in codeposition Zn-Ni alloy coatings have been carried out and the results are discussed.     

On the layer sequence and morphology in solid-state displacement reactions

In displacement reactions of the type pA+B_qXqB+A_pX, two main forms of the layer sequence have been found in the reaction layer, namely, A/A_pX/B/B_qX and A/B/A_pX/B_qX. In this paper it is argued that the thermodynamics of the system, more specifically the dependence of the activity of element X on the mole ratio between the elements A and B, determines the initial layer sequence. Various morphological variants of the two basic types may develop because of the kinetics. The prediction of the layer sequence and morphology made on the basis of this theory has been verified on a number of oxidic and sulfidic systems. It is, however, pointed out that these predictions also can be applied to purely metallic ternary systems and to other types of reactions.     

Phase and structural transformations in the alloy on the basis of the orthorhombic titanium aluminide

Phase and structural transformations in the Ti-24.3 Al-24.8 Nb-1.0 Zr-1.4 V-0.6 Mo-0.3 Si (at %) alloy that take place during heating in the temperature range of 700–1050°C have been investigated. The temperature ranges of existence of the O + β, O + β + α₂, β + α₂, and β phase fields have been established. A scheme of the relationships between the volume fractions of the O, β, and α₂ phases depending on the temperature of heating of the alloy have been investigated. The formation of an ordered incommensurate ω (V _ω) phase has been revealed in the alloy during quenching from 900°C. The existence of a correlation between the hardness properties and changes in the phase composition and morphology of particles precipitating in the alloy has been shown.     

Influence of cations and anions on the formation of β-FeOOH

In the presence of cations such as Cr³⁺, Cu²⁺ and Ni²⁺, and anions such as and , precipitation of β-FeOOH from Fe³⁺-solution containing Cl⁻ by hydrolysis have been investigated by means of X-ray diffraction technique (XRD), Mössbauer spectroscopy (MS) and transmission electron microscopy (TEM). XRD peaks of β-FeOOH were broadened when the cations were added as sulfates, and this tendency for Cr³⁺ was significantly observed. When the cations were added as nitrates, there was no significant change in XRD peaks. Inductively coupled plasma (ICP) analysis showed that only Cr added as sulfate was contained in β-FeOOH. Ni and Cu added as sulfates, and any cations added as nitrates were not contained in it. When β-FeOOH was synthesized with Na₂SO₄, the XRD peaks were broadened. XRD-peak broadening was mainly caused by the coexistence of ion. The incorporation of cations in β-FeOOH is affected by coexistent anions, and the XRD-peak broadening is caused by not only cations but also anions. This behavior has been discussed in association with the stability of Fe³⁺-complexes in the solution.     

中国铝加工业发展的成就与趋势及问题

经过半个多世纪的发展,中国铝加工业取得了举世公认的辉煌成就。特别是改革开放以来的持续高速发展,使中国已经成为世界铝加工的大国,并向铝加工强国迈进。较详细地介绍了中国铝加工业在产能、产量、装备技术、产品质量、外贸出口等方面所取得的成就,阐述了中国铝加工业发展的趋势,并指出了中国铝加工业发展中的问题。     

High stress abrasive wear behavior of sillimanite-reinforced Al-alloy matrix composite: A factorial design approach

An attempt has been made to explore the possibility of using a natural mineral, namely sillimanite, as dispersoid for synthesizing aluminum alloy composite by solidification technique. The abrasive wear behavior of this composite has been studied through factorial design of experiments. The wear behavior of the composite (Y _composite) and the alloy (Y _alloy) is expressed in terms of the coded values of different experimental parameters like applied load (x ₁), abrasive size (x ₂), and sliding distance (x ₃) by the following linear regression equations:

Electrochemical behaviour of iron in methanol and dimethylformamide solutions

The electrochemical behaviour of pure iron in methanol solutions has been investigated. The build-up and stability of a passive state has been evaluated by varying the water content and the concentration of Cl^? ions. The water content turns out to be the determining factor for passivity; the presence of Cl^? does not allow the build-up and maintenance of the passive state. Iron is always found in solution as Fe²⁺. Further experiments have been carried out in dimethylformamide, in order to determine the influence of variations in dielectric constant and in dipole moment of the medium.