Jingang Qi

VISCOSITY OF LIQUID ALUMINIUM MODIFIED BY ELECTRIC PULSE

The modification of liquid metal by electric pulse (EP) is a novel method for grain refinement. In this work, based on the reported structural heredity of EP-modified liquid aluminum, we investigated its viscosity change by using torsional oscillation viscometer. The results validate the viscosity of EP-modified liquid aluminum also decreases with increasing temperature and meets approximately exponential correlation on the whole. Moreover, it is especially important that the EP-modified liquid aluminum has the higher viscosity and possesses the bigger viscous-flow cluster in a certain temperature range, which should be associated with the increase of the order degree of its liquid structure. Differential scanning calorimetry (DSC) measurement also confirms that viewpoint. These coupling results experimentally testify the proposed mechanism of electric pulse modification (EPM) modeled merely by postulation.

Determination of retained austenite content in Fe–Cr–Ni weld metal

Abstract Several techniques, including dilatometry, X-ray diffraction, electron backscattering diffraction and magnetisation measurement, were applied and compared in order to reliably determine the retained austenite content of Fe–Cr–Ni steel weld metal. In this work, based on a proposed novel numeric solution for martensite transformation kinetics, it was found that the dilatometric method presented consistent results along with the magnetisation method in the quantification of mechanically unstable or stable retained austenite. By contrast, the X-ray diffraction method was inaccurate and time-consuming for the measurement of mechanically unstable retained austenite. However, the X-ray diffraction method was relatively successful when the retained austenite was mechanically stable. In addition, the magnetisation method seemed to be the only reliable way to detect small amounts (less than 5 vol.-%) of retained austenite in Fe–Cr–Ni weld metal.

Structure transformation of liquid aluminium modified by various electropulse parameters

Abstract In this paper, the structural transformations of liquid aluminium modified by different electropulse technique parameters were examined using high-temperature X-ray diffractometer and differential scanning calorimetry apparatus. The results showed that the structure changes depend on the modifying time and temperature. A decrease of the modifying time could result in an obviously weaker principal peak in the structure factor curve compared to the optimal electric pulse technique parameters, but slight increases of coordination number (Ns), correlation radius (rc) and average atom number per cluster (Nat) were still observed. On the other hand, the structure factor curve of the electropulse-modified liquid aluminium at the high modifying temperature of 850°C tended to be overlapped with that of the unmodified during the principal peak range. In this case, the competition result between the effect of electropulse-induced high degree of order and the destruction of superheating determined the final microstructure of the electropulse-modified liquid aluminium.

Al doping effects on ZnO nanostructure and growth mechanism

Abstract High-energy and large surface Al-doped ZnO nanostructure arrays were fabricated using hydrothermal methods under the action of pulsed electromagnetic field. The morphology, structure and component features were analysed by field emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. Results showed that the hexagonal sheet like Al-doped ZnO regularly interlaced with each other and vertically grew on the FTO substrate. The surfaces of the ZnO nanosheets were larger than those of the undoped ZnO nanorods. In addition, the formation mechanism of Al-doped ZnO nanostructure was explained.