Papers by Author: Jian Zhong Wang

Abstract: In the unmodified and EP-modified melt of Q235 steel, the solidification behavior including the nucleation and growth of crystals has been observed in situ by use of a confocal scanning laser microscope combined with an infrared image furnace, and meanwhile, described the characteristic of phase transformation. The result shows that the every stage of phase transformation is advanced; the phase transformation time is shortened, and temperature is reduced during heating proceeds. On the other hand, it can be observed that the nucleation density of solid phase increases and has an even distribution among the liquid phase.

Abstract: Well-aligned ZnO nanorod arrays had been successfully prepared by using hydrothermal methods. XRD and SEM analysis showed ZnO nanorod arrays had well orientation along the [0 0 1] direction of ZnO nanorods. The length to diameter is biggest among these samples and is about 25 when solution concentration is 0.8mol/l. The UV emission caused mainly by exciton combination. Furthermore the formation mechanism of ZnO nanorob arrays was studied in detail.

Abstract: Hypereutectic Al-Si alloy are desirable and promising for many structural applications. The influences of electric pulse parameters on Al-22%Si-1.5%Cu alloy by using OM (optical microscope) analysis along with wear test had been investigated. This work focused on studying the comparison of its solidification structure and wear resistance property with and without electric pulse treatment, respectively. The results indicated that EPM (electric pulse modification) treatment with different voltage parameters along with the frequency parameters both had the remarkable effects on micro-structure, and the grain size of alloy was refined gradually with the increase of pulse voltage or frequency. The wear resistance property of the alloy was enhanced by electric pulse treatment. It was observed from DSC cooling curve that the precipitation peak point of primary silicon was delayed by electric pulse modification comparing to the original sample without electric pulse treatment, which was analyzed to play a critical key in the alloy grain refinement.

Abstract: Li-doped ZnO thin films were grown on quartz substrates by radio frequency magnetron sputtering and In-situ annealing. The structural, electrical and optical properties of Li-doped ZnO films strongly depend on the annealing oxygen pressure. XRD and AFM analysis indicate that the ZnO films possess a good crystallinity with c-axis orientation, uniform thickness and dense surface. Optical transmission spectra show a high transmittance (~85%) in the visible region. Hall measurement demonstrates that ZnO films have p-type conduction with a Hall mobility of 5.0 cm²/Vs, resistivity of 0.97Ωcm and carrier concentration of 1.60×10¹⁷cm^-3 when annealing oxygen pressure is 1Pa.

Abstract: Transparent ZnO:Al films deposited by RF/DC magnetron sputtering in room temperature are annealed under gaseous ammonia ambient and air ambient, respectively. The characteristics of ZnO films are examined by XRD, SEM, Hall measurement and optical transmission spectra. The XRD and SEM analysis shows that both films are crystallized in the wurzite phase with a preferential orientation along the c-axis and have a smooth dense surface. Hall measurement results indicate ZnO:Al films annealed under ammonia ambient convert to p-type conduction with the high carrier concentration of 8.3×10¹⁸ cm^-3. Optical transmission spectra show a high transmittance (~85%) in the visible region.

Abstract: The influence of different broaching rate, the training of thermo-mechanical cycle and Electro-pulse Modification (EPM) on the shape memory effect of the FeMnSiCr alloy was investigated. The recovery pulling force can be realized as high as 22850N after EPM treatment. The Fe-based shape memory alloy (SMA) pipe joint can meet the requirement of engineering application.

Abstract: It was investigated that the effect of electric pulse modification (EPM) on the hot tearing of Al-5%Cu-0.8%Mn alloy. The results indicate that hot tearing tendency of all samples can be reduced treated by electric pulse with different parameters, moreover, hot tearing stress of alloy with EPM was enhanced 3 times or so than that of samples without treatment. Decreasing the quantity of eutectic in grain boundaries, decreasing the end-solidifying temperature of the alloys, and refining the grains are main causations for increasing hot tearing resistance of Al-5%Cu-0.8%Mn alloy by electric pulse modification.

Abstract: It was investigated that the effect of electric pulse modification (EPM) on the hot tearing of Al-5%Cu-0.8%Mn alloy. The results indicate that hot tearing tendency of all samples can be reduced treated by electric pulse with different parameters, moreover, hot tearing stress of alloy with EPM was enhanced 3 times or so than that of samples without treatment. Decreasing the quantity of eutectic in grain boundaries, decreasing the end-solidifying temperature of the alloys, and refining the grains are main causations for increasing hot tearing resistance of Al-5%Cu-0.8%Mn alloy by electric pulse modification.

Abstract: In this paper, the effects of electric pulse on solidified structure and graining process of near eutectic Al-5%Cu alloy have been investigated during solidified process. It was treated with different pulse voltages at 740°C in this experiment, and established the cooling curve. The results show that the improvement of alloy casting macro-segregation and solidification structure refinement by electric pulse discharging; The change of the solidified casting structure has a preferable coincidence relation with the change of the cooling curve, and analysis of the cooling curve shows that the best granular effect has a maximal supercooling on the curve.

Abstract: Taking the hypereutectic Al-Si alloy as the research object, the fading characteristics of Al-22% Si alloy at different pulse temperatures are investigated in this paper in order to analyze the mechanism of electrical pulse modification to the alloy. We can get the conclusion by observing the microstructure of the sample, measuring the microhardness and calculating the volume fraction and the average size of primary silicon: at different pulse temperatures, the effect of electric pulse modification is fading with static duration prolonging; meanwhile, with the temperature upward, the modification effect and fading trends to be weak, which indicates the best pulse temperature is one of the important factors to influence the modification effect.