Microstructure and XRD analysis in the brazing zone of a new WC-TiC-Co hard alloy

The microstructure and phase constituent near the brazing interface of a new WC-TiC-Co hard alloy was investigated by means of a scanning electron microscope, X-ray diffraction and an electron probe microanalysis. Test results indicated that the brazing joint with the interface combined excellently and can be obtained by using a Cu-Zn-Ni brazing filler alloy and by controlling the technology parameters. The microstructure of the brazing filler alloy is α+β eutectic. The brazing interface consists of WC, TiC, CuZn (α phase), and α-Co phase. There are no micro defects (such as microcracks, inclusions, etc.) near the interface.     

Characterization of electrochemically deposited Cu-Ni black coatings

Electrochemically deposited Cu-Ni black coatings on molybdenum substrate from ethylenediaminetetraacetic acid (EDTA) bath solution are shown to exhibit good optical properties (α=0.94, ε = 0.09). The deposit is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Cu is present in metallic and +2 oxidation states in the as-prepared Cu-Ni black coating, whereas Ni²⁺ as well as Ni³⁺ species are observed in the same coating. Cu and Ni are observed in their metallic state after 10 and 20 min sputtering. X-ray initiated Auger electron spectroscopy (XAES) of Cu and Ni also agrees well with XPS investigations.     

Quantitative analysis of the microstructural homogeneity of zirconia-toughened alumina composites

The Voronoi diagram approach was applied to quantify the level of microstructural homogeneity of ceramic ZTA samples. From SEM pictures of polished cross-sections of ZTA samples a point pattern representing the distribution of the zirconia phase in the composite was generated. This point pattern was converted into a Voronoi diagram. The level of microstructural homogeneity was quantified by statistical analysis of the relevant properties (area, perimeter and number of faces) of the Voronoi polygons. A dimensionless parameter defining the level of microstructural homogeneity was calculated from the different sets of statistical data. The calculated parameters indicated significant differences in homogeneity between the ZTA samples. These differences were in qualitative agreement with previously published wear rates of the same ZTA composites. This illustrates the relevance of microstructural homogeneity for wear performance.     

Effect of liquid-forming additives on the sintering and mechanical properties of Al2O3/3Y-TZP (30 vol.%) composite

Al₂O₃/3Y-TZP (30 vol.%) composite was pressurelessly sintered with addition of TiO₂MnO₂ and/or CaOAl₂O₃SiO₂ glass. It was found that TiO₂MnO₂ addition greatly enhanced the densification of the composite by the formation of a low-viscosity liquid at sintering temperature. In contrast, the high-viscosity liquid formed by CaOAl₂O₃SiO₂ glass improved mechanical properties because of its repressing effect on grain growth. The composite could be obtained at a temperature as low as 1400°C by co-doping with TiO₂MnO₂ and CAS glass. Bending strength of 552±64 MPa and fracture toughness of 6.03±0.22 MPa m^1/2 were obtained with a doping level of 2 wt.% TiO₂MnO₂ and 2 wt.% CAS glass.     

电子束辐照下富氢镜质体生烃标志

IntroductionThetransfOrmatiOnfrOmorganicmaterialincoalseamtohydrocarbonmainlyoccursunderthethermaldegradationeffectoforganicmatters.TheabilityOfcoaltoformliquidhydrocarbonanditsconstitutionfeaturesiscloselyrelatedwiththecOntentofliptinite(includinghydrOge…     

Abrasive wear micromechanisms of oriented polymers

For successful use in textile applications, synthetic fibres must have an excellent wear resistance. This paper analyses the wear micromechanisms of polymeric fibres as a function of microstructural parameters such as molecular orientation and degree of crystallinity. A series of poly(amide) 6 fibres differing in their molecular weight has been studied under abrasive wear conditions. From an examination of the wear kinetics, it was concluded that the nature of wear macromechanisms is independent of the experimental conditions and fibre molecular weight. By means of wide angle X-ray scattering, it was shown that the level of molecular orientation within the amorphous phase was correlated to the wear damage resistance. From these observations, an interpretation of the wear micromechanisms is proposed. It relies upon the localised cavitation of microvoids within the interfibrillar amorphous domains of the microfibrillar structure under the abrasive action of the sliding micro-asperities. The coalescence of these microvoids activates relative displacements between microfibrils, which eventually leads to the splitting of clusters of microfibrils and wear losses. A combination of this material loss with creep results in fibre failure. The observed micromechanism emphasises the role of the molecular orientation on wear resistance.     

A simple semiempiric model for NMR relaxometry data of hydrating cement pastes

In this contribution, results from NMR relaxometry experiments on hydrating white cement pastes are presented. Nonexponential effects are discussed and quantified by stretched-exponential analysis. From the magnetization decay curves in transverse relaxation experiments, the degree of hydration is estimated and a semiempiric model is proposed describing the relationship between the microstructure development in the hydrating cement and the degree of hydration.     

激光快速成形过程熔池行为的实时观察研究

通过建立近距离连续拍摄系统实现了对激光快速成形过程中熔池行为的实时观察,并采用图像分割算法获得了熔池侧视形态,结合熔覆试样的定量金相法获得的熔池前视形态,对熔池进行了定量表征。结果发现,熔池的长度和宽度与光束直径相当,熔池自由表面呈圆弧形并向外凸起,最大熔深处熔池自由表面法向和激光束轴线之间存在夹角,表明熔池向激光束轴线方向倾斜,而熔池在液态存在时间较短,例如光束直径为4mm,光束扫描速度为5mm/s时,熔池在液态存在时间小于1秒。激光熔覆区的高速摄影实验结果发现,随金属粉末的射入,熔池的几何尺寸逐渐减小,熔池后沿不断抬高,最大熔深处熔池自由表面法向和激光束轴线之间的夹角由1度左右逐渐增大到25度左右,导致熔池中局部凝固条件发生改变,从而影响到局部熔覆层的微观组织。     

The application of information entropy to the estimation of three-dimensional grain or particle size distributions from materialographic sections

Information entropy was applied to size class selection for the unfolding of grain size distributions and the results were compared with traditional forward and inverse methods using arbitrarily selected size classes. This comparison shows that information entropy provides a better representation of the data.