Papers by Keyword: Electric Pulse Modification (EPM)

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: 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: 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.

Abstract: The modification of liquid metal by electric pulse (EP or EPM) is a novel method for improvement of solidification structure. In this study, the as-cast texture of EP-modified pure copper was investigated by using X-ray Schulz backscattered method. The experimental results show that the as-cast texture of EP-modified pure copper is dissimilar with that of the unmodified. The unmodified mainly exhibits a type of {110}<001> texture, and the maximum value of orientation density is 10.07, in the plane that parallel to the vertical section along the ingot axis, the <110> crystal direction has the most volume fraction of 27.18%; By contrast, the as-cast texture of EP-modified pure copper shows a typical type of {102}<001>, and the maximum value of orientation density is 12.88, at the same time, the corresponding <102> crystal direction changes to be the most volume fraction and its value is 22.82%. These facts indicate that the crystal orientation (texture) of solidification structure could be altered by EPM, and EPM technology would thus influence the following metal formability.

Abstract: The modification of liquid metal by electric pulse (EP) is a novel method for grain refinement. In this study, based on the reported structural heredity of EP-modified liquid aluminum, the structure tests of EP-modified liquid aluminum were conducted by using high temperature X-ray diffractometer. The results show that the EP-modified liquid structure also tends to be slack and unordered with increasing temperature, which is similar to that of the unmodified. However, the quantitative characterization denoted by the liquid structure parameters exhibits their discrepancy. At the modifying temperature of 750°C, the order degree of EP-modified liquid aluminum is remarkably strengthened and the value of average atomic number per cluster changes from 119 (no EP) up to 174 (EP) by an increase of 46%. These tests experimentally testified Wang’s electric pulse modification (EPM) model that was built only by phenomenology and hereby the mechanism of grain refinement resulting from EPM is further elucidated.

Abstract: The modification of liquid metal by electric pulse (EP, EPM) is a novel method for grain refinement. In this study, based on the reported structural heredity of EP-modified liquid aluminium, the structure tests of EP-modified liquid aluminium with different technique parameters were conducted by using high temperature X-ray diffractometer. The results show that the quantitative structure changes of EP-modified liquid aluminium have a close relationship with the modifying time and modifying temperature. The decrease of modifying time could result in an obvious weaker principal peak in structure factor curve compared with the optimal EP technique parameters, but a slight increase of coordination number (Ns), correlation radius (rc) and average atom number per cluster (Nat) is still observed under this condition. These facts indicate that the EP-modified liquid aluminum could gain an increasing order degree, and thus have an advantage during the formation of a stable nucleus, eventually leading to a grain-refining solidification structure. On the other hand, the structure factor curve of EP-modified liquid aluminum at the high modifying temperature of 850°C tends to be overlapped with that of the unmodified during the principal peak range. In this case, the competition result between the EP strengthening effect and the destruction of superheating would determine the final structure of EP-modified liquid aluminum.