Key Engineering Materials Vols. 280-283

Abstract: A universal model for describing the wetting kinetics at solid/liquid interfaces, where interfacial chemical reaction occurs, is proposed, whereby four distinct stages separated from each other by transition points are anticipated. The stages are described by means of comparing the dimensions of the base of the liquid sessile drop with the evolution of the reaction product forming on the solid/liquid interface, over time.

Abstract: A new approach was developed for surface modification of metallic surface. By treating nano-zirconia particles and metal surface in different charge state, nano-zirconia particles can be dispersedly inlaid in metal surface owing to electrostatic and nanometer effects. By using this method, metal components of complex shapes, especially those having inside surfaces, might be easily improved, i.e., enhanced surface hardness and wear rate.

Abstract: To solve the difficult problem of selecting processing parameters of plasma arc cutting ceramic (PACC), the heat conduction model of PACC has been established and the calculating formulations of temperature field have been derived. Then, the distributions and influence factors, such as arc power, cutting speed and workpiece thickness, of temperature field of the ceramic plate and the anode plate have been studied. Based on the work above, the required arc power can be calculated. Moreover, the relation between thickness of ceramic plate and anode plate can be determined, which provides a helpful reference for selecting the thickness of additional anode plate.

Abstract: A novel technology of metal-ceramic parts with special functions formed by plasma spraying has become an important research trend. In this paper, the technical characteristics and spray parameters have been analyzed in detail based on the experiments of metal-ceramic near net forming, and some important techniques such as spray mould fabricating, backing and demoulding have been researched and summarized. Furthermore, the microstructure and property have been analyzed to forecast the quality of spray-formed parts. The research results show that plasma spraying is suitable for the production of metal-ceramic parts of any size with special mechanical and thermomechanical properties, which can realize the contemporary integration of forming and machining. Therefore, this technology with simple process and low cost is a method of metal-ceramic fabrication with a broad and brilliant prospect.

Abstract: Pores in ceramics have their peculiarity different from common porous materials, so the existing characterization methods should be re-recognized. In the present work, thermal shrinkage curves adequately characterize the dynamic process of porosity evolution in ceramics, and the results are checked by Archimedes method. In order to detect pore-size distribution quantitatively, gas adsorption (BET method), mercury penetration and a new Scanning Acoustic Microscope (SAM) technique are used on Alumina ceramics with large and median pores. The results acquired by these three methods are discussed in detail and unified by the introduction of effective pore-size coefficient t. It shows that a complete characterization system adapt to pores in ceramics should be established.

Abstract: The Self-propagating High-temperature Synthesis(SHS) process is a nonlinear one far from thermodynamic equilibrium, many nonlinear structures present in the process. After SHS processes of Ti-C-Fe and Ni-Si systems have been studied by the numbers, the effects of initial parameter conditions on nonlinear structure have been gained. On the base of establishing the model of combustion reaction dynamic characteristics, backward finite-difference approximation equations and central finite-difference approximation equations were applied to numerically calculate and simulate the characteristics of combustion wave and its’ change rules in the SHS process. All the experimental results are consistent with the simulative results.

Abstract: A popular type is of metal matrix reinforced by ceramics particles. It has been revealed that the composites are susceptible to interfacial degrading, which may be dramatically detrimental to the overall properties of composites. In present paper, an equivalent inclusion type constitutive model was developed for the composites with dispersed particles on which imperfections of the material interface are incurred. Two fundamental tensors are derived, the modified Eshelby tensor and the damage tensor of the weakened particles. By applying these tensors into a carefully schemed constitutive law, the effects of interfacial degrading on the overall properties of composite materials can be investigated. The interface degrading includes sliding and debonding. The numerical results show that even with the nil resistible sliding coefficient, its effect on the overall Young’s modulus is not notable unless the volume fraction of the particle is so high as more than 70%. For the global Poisson’s ratio, when there is the sliding on the interface, the Poisson’s ration rises irrespective of the constituent material values. It is noted that even in the elastic state, the global Poisson’s ratio rises greater than that of both the constituents. This phenomenon might indicate that even at the elastic state, the particle interfacial sliding would give somewhat a plasticity-like deformation behavior. The effect of the interfacial debonding on the overall properties of the composite is more conspicuous in comparisons of the sliding. The debonding parameter greatly affects both the properties for almost entire range of the particle volume fraction. Unlike the sliding effect case, the debonding decreases Poisson’s ratio at all cases, which represents the micro-damage effect occurring in the composite.

Abstract: The paper shows a finite element method (FEM) model to calculate the temperature distribution of desulphurizing lance use in hot metal pretreatment by ANSYS program. The dynamic temperature distribution under non-linear thermal loads within lance in one or more duty cycles is obtained. The temperature distribution at important parts of the lance changes with time and is summed up according to the simulation. Some important instructional opinions offered by the conclusion benefit the improvement of temperature-based structure design and mend of desulphurizing lance. In addition, the conclusion provides research data for thermal stress analysis of lance.

Abstract: Neural network (NN) is an effective method in the filed of materials design, but the convergent speed is decided by initial weights. This paper proposes genetic neural network algorithm (GNNA) to design materials. Aluminum titanate modification is studied by the method of GNNA. The results indicate the algorithm works well.