Formation of TiC via interface reaction between diamond grits and Sn-Ti alloys at relatively low temperatures

In this paper, interfacial reaction between diamond grit and Sn-6Ti alloy was systematically studied at brazing temperatures from 600 to 1030 °C. A thin and uniform layer of scallop-like nano-sized TiC grains was formed after brazing for 30 min at 600 °C, and interfacial TiC grains subsequently coarsened as brazing temperature increased to 740 and 880 °C. Strip-like columnar TiC grains in a bilayer structure was further grown as brazing temperature increased to 930 °C. After brazing at 1030 °C, a dense layer of columnar TiC grains were formed. Based on the TEM micrographs of interfacial TiC, the formation and evolution of the growth morphologies of interfacial TiC was believed to be controlled by the diffusion of C flux from diamond grits, which is dependent on the brazing temperatures.     

Inter-diffusion Based Analytical Model for Growth Kinetics of IMC Layers at Roll Bonded Cu/Al Interface During Annealing Process

Metals and Materials International - A model based on inter-diffusion theory was established to predict growth kinetics of the intermetallic compounds (IMCs) formed in roll bonded Al/Cu sheets...     

钼圆片表面腐蚀亮点的成因浅析

以钼粉生产过程中存在的一些现象和数据为依据,在钼粉成形、烧结及钼坯后加工工艺不变的前提下,认为钼粉中Fe、Ni等杂质元素是钼圆片表面产生腐蚀亮点的原因。     

Phase Equilibria for the Aluminum-Rich Region of the Al-Cu-Co System at 883?K

The 883 K isothermal section of aluminum-rich region of the Al-Cu-Co ternary system was determined experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, x-ray powder diffraction and differential scanning calorimetry. Ten three-phase regions have been confirmed experimentally. The influence of Cu and Co content on the lattice parameters of ternary M ((Al,Cu)₁₃Co₄) and H (Al₃(Cu,Co)₂) phases, respectively were defined.     

Direct Formation of Titanium Carbide via In Situ Carbothermal Reduction of TiO2/Carbon Cladding for Coating Application

Protection of Metals and Physical Chemistry of Surfaces - In situ direct formation of titanium carbide (TiC) was realized via tungsten inert gas (TIG) arc surface cladding using titanium dioxide...     

高碳钢热轧盘条焊接区的热磷化工艺研究

针对77B高碳钢热轧盘条在线生产对其焊接区磷化质量的要求,开发了一种实用性强的锌系热磷化工艺,探讨了磷化液中各组分及操作条件对磷化膜质量的影响,并对磷化膜有关性能进行了测试.结果表明,该锌系磷化液具有稳定性高、快速、少渣、使用寿命长和生产成本低等特点;经80℃×(10～15)min喷淋处理后,盘条焊接区可获得膜重＞10 g/m2的优质磷化膜,其外观呈均匀黑色,结晶细致,附着牢固,抗蚀性好,能顺利拉拔,满足了当前高强度PC钢绞线原料--77B高碳盘条在线生产所提出的焊接头磷化质量及工艺操作要求.     

Analysis of Pore Formation at Oxide–Alloy Interfaces—II: Theoretical Treatment of Vacancy Condensation for Immobile Interfaces

Void generation at scale–alloy interfaces during the oxidation of binary alloys as a result of matter transport through the scale and of diffusion of the metal components in the alloy is examined under a number of simplifying assumptions. In particular, it is assumed that the scale–alloy interface does not displace with time and that all the metal vacancies at this interface condense there to form voids, which amounts to calculating the maximum rate of interface void production. The analysis is developed both for the case of the parabolic rate law and for a general kinetics behavior, using the experimental information concerning the kinetics of weight gain. Application of this treatment to the oxidation of FeAl at 1000°C, taking into account the gradual transformation of the initial form of alumina into the stable alpha form, predicts the presence of a maximum in the overall void volume, in qualitative agreement with experimental observations. However, the overall volume of voids measured is much smaller than the values calculated under various conditions, suggesting that an effective mechanism of vacancy annihilation must be present at the scale–alloy interface.     

Use of the Method of Acoustic Emission for Studying the Laws of Formation of Secondary Structures at Friction of Nicotrated Steels

The processes of structure formation on the surface of nicotrated steel 30KhN2MFA at friction under the conditions of life lubrication of a “brad – disk” couple are studied in a special installation, which makes it possible to continuously measure the force of friction, the temperature in the contact zone, and the signals of acoustic emission during the test. The structures formed on the surface of nicotrated steel during friction are analyzed qualitatively and quantitatively with the help of a local friction factor f _loc that characterizes friction on individual local areas. A comparative analysis of temperature dependences of the parameter f _loc and of the phase composition of the dissipative layer (“third body”) formed on the surface of the carbonitride layer during friction is performed. An empirical equation relating these two characteristics is suggested.     

A Possible Mechanism for Protrusions Formation at the Metal/Oxide Interface During Short Time Oxidation of Ferritic Stainless Steel

High temperature oxidation of ferritic stainless steel for short durations leads to the formation of an original morphology at the metal/oxide interface. This interface is composed of metallic protrusions localized in a chromium-rich oxide layer through a discontinuous silica film. In this paper we propose a mechanism based on preferential diffusion paths for the oxygen through the oxide that are governed by the distribution of the hydrostatic pressure in this layer. We point out that the mechanical contrast between the oxide and the metal subjected to creep can be critical for the hydrostatic pressure gradient magnitude inside the oxide layer. This observation is likely to promote the formation of protrusions for specific conditions of temperature and time of exposure to oxidation.     

EQCN study of anodic dissolution and surface oxide film formation at Au in the presence of Cl or Br ions: A model process for corrosion studies

The anodic dissolution of an Au electrode and associated thin-layer oxide film formation in aq. H₂SO₄ in the presence of Cl⁻ or Br⁻ ions at various concentrations provides a model process for metal corrosion. In the present work such processes were investigated using cyclic voltammetry and chronoamperometry, with complementary nanogravimetry measurements using the EQCN. The results clearly indicate that in 0.5 M H₂SO₄ electrolyte, containing 1 mM Br⁻ or Cl⁻, Au dissolves over the potential range 1.0 - 1.45 V(RHE) through a 3e oxidation process involving Au complex-ion formation that can be followed in situ by means of UV spectroscopy. The linear relationship between mass changes and reciprocal square-root of sweep-rate and between anodic currents in cyclic voltammetry at ca. 1.20 V for Br⁻ (1.39 V for Cl⁻) and square-root of sweep-rate/or electrode rotation rate indicated quantitatively that the dissolution process is diffusion-controlled. It was interesting to find that electrode rotation in the presence of Cl⁻ ions has little effect on the anodic formation of surface oxide, while, on the contrary, with Br⁻ ions present, currents for oxide film reduction are not observed at rotation rates > ca. 400 rpm.