Papers by Author: Xiang Jie Wang

Abstract: The effects of the low frequency electromagnetic field on the macrosegregation of the 7075 aluminum ingots were investigated. The 7075 aluminum ingots with the diameter of 200 mm were prepared by the conventional direct chill casting and the low frequency electromagnetic field casting (LFEC) processes, respectively. The temperature during casting at steady state was measured, and the mushy region was observed from the temperature contour. The concentrations of the alloying elements were measured by the spectrograph. It was found that the transition region was broadened, but the mushy zone became narrower with presence of the low frequency electromagnetic field. The centerline macrosegregation of the ingots was alleviated by the low frequency electromagnetic casting process.

Abstract: During the low frequency electromagnetic casting process, the electromagnetic parameter plays an important role among the casting parameters. In this work, effects of electromagnetic parameters on the electromagnetic field and body force are analyzed by constructing a two-dimensional finite element model and using ANSYS software which is a kind of commercial FEM analysis software. The results show that the current frequency mainly influences the distribution of electromagnetic body force, the current intensity determines the intensity of electromagnetic body force, and the current frequency and intensity should be matched during the low frequency electromagnetic casting process.

Abstract: Low frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Thermocouples were used to measure the cooling curves from the border to the center of the ingot during steady-state of casting process, cooling curves were obtained, and effects of low frequency electromagnetic field on the solidification, macrostructure during the conventional hot-top casting for 6063 aluminum alloy process were analyzed. The experimental results show that the forced convection caused by the low frequency electromagnetic (LFE) filed can make the melt temperature uniform, promote the evacuation of superheat, make the temperature in the liquid pool lower than the liquidus temperature of 6063 aluminum alloy, increase the number of floating nuclei, make the ingot with fine and homogeneous macrostructure, though there is no addition of any grain refiners.

Abstract: 7075 aluminum alloy ingot with the diameter of 100 mm has been produced by horizontal direct chill casting in different casting speed. The effect of casting speed on the sump profile and the ingot surface quality was studied by sump profile observation. It was found that increasing the casting speed results in the deepening of the liquid pool, the adding of segregation knots and the reducing of cold shouts in the ingot surface. It is also found that the depth of the liquid pool is directly proportional to the casting speed and the squared radius of the ingot.

Abstract: On the basis of conventional hot-top casting, low frequency electromagnetic field was applied in the process of hot-top casting to produce 7050 aluminum alloy ingot, the influences of low frequency electromagnetic field on cold-shut have been studied. The experimental results show that under the effect of the low frequency electromagnetic filed, the depth of cold folding has been decreased, and the as-cast structure has been refined. The reasons for low frequency electromagnetic field improving the surface quality, refining the structure of the ingot were summarized.

Abstract: The influence of different electromagnetic fields on the horizontal direct chill (HDC) casting of aluminum alloy is studied. 7075 aluminum alloy with 100-mm in diameter is produced by HDC casting process; single electromagnetic field located before or around the mold and an out-phase electromagnetic field (OPEMF) are applied in the HDC casting process. The effect of different electromagnetic fields on the HDC casting solidification behavior and as-cast structure is investigated. The electromagnetic field can effectively make uniform thermal distribution in the molten pool and refine the as-cast structure. The OPEMF is more efficient than the single electromagnetic field in improving the as-cast structure of HDC cast ingots.

Abstract: Hot tear is one of the main defects during the aluminium casting process, and it usually occurs during solidification. In this work, the low frequency electromagnetic field was applied to study the effects of low frequency electromagnetic field on hot tear during the conventional hot-top casting process. The results show that under the effect of the low frequency electromagnetic field, the structure of the ingot is refined, the flow direction is changed, and the depth of the sump becomes shallow. All these factors can decrease the hot tear susceptibility.

Abstract: The effect of increasing the amount of added grain refiner and combination electromagnetic filed on grain size and morphology has been investigated by die casting of commercial aluminum. The results show the grain size and the grain morphology both are transited with the increasing of the addition of Al-5Ti-B. The grain size continuously decreased with increasing the addition of grain refiner. Without grain refiner additions, an obvious transition in grain size and morphology is observed with the application of low frequency electromagnetic field (LFES). The efficiency in grain refinement of LFES decreases with increasing the amount of grain refiner. However, even when the addition of grain refiner is 2 wt. % Al-5Ti-B, 63 % grain size reduction still is observed by the affect of LFES. This result shows that the LFES can enhance the efficiency in grain refinement of grain refiner.