Papers by Author: Xian Liang Zhou

Abstract: The fabrication process and fracture characterization of 35 and 65 vol% SiCp particulate-reinforced Al matrix (SiCp/Al) composites have been investigated. SiCp composites having different volume fractions of the n-SiCp were synthesized via by pressureless-infiltration at near-net-shape route and were uniaxially tested at room temperature. The SiC particles were mixed with silicasol as an inorganic binder in distilled water. The mixtures were consolidated in a mold by pressing and dried in two step process, followed by calcination at 1000 °C. The SiCp/Al composites were fabricated by the infiltration of Al melt into SiC performs. The experimental results show that volume fraction of reinforced particles in SiCp/Al composites had a significant influenec on fracture section surface characterization in tensile tests. Composite with 45 vol% SiCp, fracture was firstly happen in Al matrix, shallow dimples and intergranular fractures were seen in all the fractographs. With increasing of vol% SiCp, fracture was more brittle in appearance in the composites and the fracture surfaces were flat and less plastic deformations.

Abstract: ZL101 Al alloy reinforced with 55% silicon carbide particulate metal-matrix SiCp/Al composite has been fabricated by pressureless-infiltration. The microstructure characterization of composite has been studied by optical microscope (OM), scanning electron microscope (SEM), X-ray spectroscopy (EDX), respectively. The results show that the SiCp are uniformly distributed in Al alloy matrix, however, there are some casting defects such as shrinkage and gas porosities in the matrix. When Mg was added into the composite, it can improve wettability property of between Al matrixes and strengthen particle SiCp and decrease micro-defects such as gas porosities, the Microstructure of SiCp/Al composite prepared was compact and uniform. The SiCp particles evenly distributed in the matrix and without significant partial segregation phenomenon. It improves the whole performance of the composites.

Abstract: The growth of polycrystalline curved surface diamond film using direct current plasma jet CVD (DCPJCVD) is measured by those techniques. The relationships between morphology, microstructure, and film quality are investigated by scanning electron microscopy (SEM) and Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), respectively. The results show that, after molybdenum substrate was polished by series of diamond powder, atom hydrogen etching, respectively, a much higher nucleation density can be achieved. Synthetic diamond film is compact, continuous and uniform, and diamond film grows with the columnar spreading from the nucleation surface to the growth surface, (111) faces were dominant in polycrystalline texture diamond film. Raman spectrum indicates that there is only diamond characteristic peak in diamond film, and high quality curved surface diamond film was prepared. IR transmittance of curved surface diamond film in the range of 750 - 4300 cm-1 reached about 60%. Meantime, the IR transmittance was almost the same in the central and fringe regions of the film. These properties indicate that curved surface diamond film has a promising application in infrared windows and dome.

Abstract: SiCp/Al composite was fabricated by the method of pressureless-infiltration. In atmospheric environment, the atmospheric corrosion behavior of SiCp/Al composites (ZL101+49%SiC+5%Mg) was studied by mass loss, optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FTIR), respectivelhy.The results show that the corrosion rate of the SiCp/Al composites increases with increasing of time in atmospheric environment. Pitting corrosion is the main characteristic of SiCp/Al composite, and corrosion area gradually extends around with time increasing. At last, sheet like corrosion substrates distribute in the surface of n the SiCp/Al composites. Amorphous Al2O3 and amorphous AlxSO4yOHz are the main corrosion products.

Abstract: SiCp/Al composites based on different matrix elements Mg and Si content were fabricated by pressureless infiltration. Through microscope investigation by SEM and TEM, density examination, coefficient of thermal expansion (CTE) and thermal conductivity measuring by Netzsch DIL 402EP and Netzsch LFA 447 Nanoflash, the effects of Mg and Si in the aluminum on the thermo-physical properties of SiCp/Al composites was studied and analysed. The results showed that , adding Mg element in matrix enhaced the densification and thermal conductivity of composites, but meanwhile increased the CTE of SiCp/Al composites. When Mg element content was in higher than 6.3wt%, CTE of SiCp/Al composites increased obviously. Adding Si element in matrix markedly reduced the CTE of composites , but meanwhile decreased thermal conductivity of composites. When Si element content was higher than 5-9wt%,thermal conductivity of composites declined obviously. Adding Mg element in matrix improved the interface wet ability between molten aluminum and SiC particles, and adding Si element in matrix could control the formation of A14C3 which is a detrimental interface reaction product during the pressureless infiltration processing. Therefore, adding appropriate Mg in company with Si in matrix will be more benefit to enhance the integer properties of SiCp/Al composites.

Abstract: In this paper, using high tensile strength and yield strength of hot-rolling acid washing thin steel sheet instead of cold-rolling steel sheet as the vehicle frame is investigated. The high pure and finer grain steel can be obtained by deep deoxidation technology, deep desulfurization technology, low nitrogen and microalloy-technology of Boron/Niobium/Titanium. High yield strength (σs>340 MPa) and high specific elongation hot-rolling thin steel sheet have been produced in the EAF-CSP short flow product line. The mechanical property, shape, surface quality and tolerance of steel sheet after hot-rolling can be controlled by optimizing joining-casting-rolling and controlling-rolling-cooling technology. Based on the forming test, cold-bending test, welding test and fatigue test results, it can be seen that cold-bending property, forming ability and fatigue strength of hot-rolling acid washing steel sheet is better and meet the product requirement of vehicle frame. This investigation can resolve the fracture problems of QUANSHUN vehicle, improve the working life, provide reliable automobile and reduce the production cost.

Abstract: The influences of the different Si (0.723%~4.5%) and Cr (2.0%~8.0%) contents on the microstructures and properties of Cr-Si-Mn white cast iron were investigated. It is shown that with increasing of amounts of Si and Cr elements, carbide undergoes an evident change in the morphology from the continuous net to isolated stripe and becomes clearly finer, even forms chrysanthemum-like microstructure which is usually found in high Cr white cast iron. Additionally, the amounts of the carbides increase too. The XRD analysis shows that the carbides are a mixture of Fe3C and Fe7C3 phases. Furthermore, the hardness of carbide and matrix is also found to progressively increase with increasing of amounts of Si and Cr elements. The hardness of the matrix in as-cast white cast iron is over HV400, suggesting that the matrix consists of martensite and bainite phases. The impact toughness of the samples declines evidently when Si content excesses 3.0wt%. It is also revealed that the bainite matrix in the Si-Cr white cast iron has a higher impact abrasive wear resistance than others, which is almost not dependent upon heating temperature and cooling rate. When Cr content approaches 5wt%, the impact wear resistance of the new cast iron is comparable to that of the traditional high Cr cast iron.

Abstract: Al alloy reinforced with SiCp (size: 70-220μm) was fabricated by pressureless-infiltration. Its wear resistant property was investigated under different heat-treatment conditions, and morphology of worn surface was examined. The results showed that the composite was integrated, uniform and compact, and its wear resistant property was better than that of the unreinforced matrix alloy. It was indicated that some rigid SiCp in the abraded surface of the composite could support part of loads and replace matrix to wear-tear, which improved the wear resistant property. Compared to annealing, solution aging strengthens Al alloy matrix and cohesion with SiCp, and the wear resistant property of composites was better. Combining interface is also an important factor which influences on wear resistant property. During the wear test, the smaller SiCp size, the more interfaces, there are more SiCp falling off because of loosening combining interface, which results in more wear-tearing value. The wear rate of composite increases with decreasing SiCp size, thus, the composite with larger SiCp has better wear-resistant property than that with smaller SiCp. At last, the wear mechanism of the composite was also studied, and it showed that abrasive wear dominated in the abrasion process.