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In this work, a Ti45Al45Nb5Mo5alloy was prepared by non-self-consuming vacuum arc melting furnace. The effects of heat treatment on the microstructure and mechanical properties of the alloys were investigated. The alloy was heat treated in a vacuum at temperatures of 1150 °C, 1200 °C, 1250 °C and 1300 °C with a holding time of 30 min and then cooled in a furnace. The microstructure of the alloy after heat treatment showed a coarsening phenomenon. The bright linear precipitated phases in the α2/γ lamellar structure diffused along the lamellar orientation. However, the lamellae exhibited significant deterioration after heat treatment at 1300 °C. The microhardness of the alloy improved by the heat treatment and the alloy had the highest microhardness of 414.4 HV after heat treatment at 1250 °C. At the same time, the heat treatment also significantly improved the plasticity of the TiAl alloy. The alloy exhibited the highest compressive strength and elongation at break of 2220 MPa and 39.9% after heat treatment at 1250 °C. The increase in microhardness was primarily attributed to the reduction in interlamellar spacing and the increase in strength due to solid solution. All variations in matrix phases, interlamellar spacing and grain size significantly affected the compressive properties of the alloy.

NiAl-based composites were fabricated in-situ using vacuum hot-press sintering technology. The Ti3AlC2, TiC and Ti3Al were formed during the sintering process, and the intensity of peaks grow higher with the addition of Al, Ti and C powder contents, respectively. The microhardness of the composites was significantly improved by adding these powders and gradually increased with the incremental content of Al, Ti and C powders. Meanwhile, the tribological properties of the composites at high temperature were also improved. The worn surface formed during the tribo-oxidation reactions and produced the glaze film in the high-temperature friction process, which could improve the composites' tribological properties. The TiO2and Al2O3phases were observed on the worn surface after the friction test, which could act as a high-temperature lubricant and improve the composites’ tribological properties.

This paper analyses the influence of remelting process on the microstructure characteristics and wear behavior of NiCrBSi alloy coatings. Two different remelting processes are investigated to obtain improvement in properties: flame spraying combined with flame remelting and flame spraying combined with induction remelting. A comparison of the microstructure and the tribological behavior is presented. A field-emission gun scanning electron microscope, energy dispersive X-ray microanalysis and X-ray diffraction analysis have been used to observe the microstructure characteristics of the coatings. The results reveal significant differences in the morphology, distribution, size and percentage of the phases of both coatings. The induction remelting technique results in higher Vickers hardness, excellent wear resistance and good remelting quality.

Abstract

In this work, Ni-based alloy coatings with different CeO2rare earth oxide contents were deposited on carbon steel by flame spray and fusing processing. The tribological behavior of the coatings was studied using a ball-on-flat wear tester under dry sliding, ambient conditions. Hardness testing, field emission gun scanning electron microscopy with attached energy dispersive spectroscopy and oscillating friction and wear testing were employed to characterize the microhardness, microstructure and tribological properties of the coatings. The results indicated that the addition of an appropriate amount of CeO2could refine and purify the microstructure. The coatings containing 5 wt% CeO2exhibited the highest wear-resistant properties. Moreover, a new compound phase, Ce2Ni21B6, was formed within the coatings, such that the microhardness values containing this phase were higher than those in the other coatings. Finally, the effects of CeO2on the coatings and the mechanism describing the sliding wear were discussed.

A kind of cylindrical dynamic system with impulsive state feedback control is formulated and investigated. Based on the qualitative properties of the corresponding continuous system, the existence of order-k(k∈Z+)periodic solutions of the cylindrical dynamic system with impulsive state feedback control is discussed on the cylinder with perimeter 2π. If the equilibrium of the corresponding continuous system in the rectangle coordinate system is an unstable node, then the cylindrical dynamic system has two one-side stable minimum limit sets. If the equilibrium is an unstable focus, then, for different parameters, the cylindrical dynamic system has the periodic solutions with different periods and different orders. Finally, numerical simulations are given to verify the theoretical results.

Interaction Article Classification (IAC) is a specific text classification application in biological domain that tries to find out which articles describe Protein-Protein Interactions (PPIs) to help extract PPIs from biological literature more efficiently. However, the existing text representation and feature weighting schemes commonly used for text classification are not well suited for IAC. We capture and utilise biological domain knowledge, i.e. gene mentions also known as protein or gene names in the articles, to address the problem. We put forward a new gene mention order-based approach that highlights the important role of gene mentions to represent the texts. Furthermore, we also incorporate the information concerning gene mentions into a novel feature weighting scheme called Gene Mention-based Term Frequency (GMTF). By conducting experiments, we show that using the proposed representation and weighting schemes, our Interaction Article Classifier (IACer) performs better than other leading systems for the moment.

In this paper, we consider a predator-prey system with stage structure. The populations have two stages, an immature stage and a mature stage, the age to maturity is represented by a time delay, which leads to systems of retarded functional differential equations. We obtain the conditions for global asymptotic stability of two nonnegative equilibria of this system. The numerical simulation suggests that time delay has both oscillatory dynamics and stabilizing effects.