Electromagnetic Field On Al-1%Si Aluminum Alloy Solidification Control

The Al-1%Si alloy is an important metal material. And it is mainly used in the bonding wires of electronic packaging to connect chip with external port in the integrated circus, the functional thin film materials on the silicon substrate for integrated circus and the ion sputtering target which is sputtered on the integrated circuit board, and then carved conductive line. So, the ingots of Al-1%Si alloy must have the high quality. The solidification structure of ingots should be fine and evenly distributed throughout the internal ingots to ensure that the ingots have good mechanical properties. Meanwhile, the distribution of solute Si element in the ingots is also uniform, which does not exist the serious segregation. According to these requirements of Al-1%Si alloy, the IF soft-contact electromagnetic field and pulse electromagnetic field were applied to obtain the high quality ingots in this dissertation. The paper’s main contents are as follows:The IF electromagnetic field of1000Hz,30.4kW was exerted in the process of continuous casting high purity’s Al-1%Si alloy to utilize the disturbance generated by the electromagnetic field to refine and improve the solidification structure of the ingots. The results showed that the ingot’s quality was apparently improved via exerting the IF electromagnetic field. By comparison the DCC ingots with the EMCC ingots, the distribution of the Al-Si eutectic phase from the aggregated distribution on the coarse boundaries to the small granular and short rod dispersion distribution on the refine boundaries and in the refine grains was found. The grain refinement and the distribution of Al-Si eutectic phase make the ingot’s mechanical properties be greatly improved. The average ultimate tensile strength of the EMCC high purity Al-1%Si alloy’s standard tensile specimens was106.3MPa, and the DCC was64.1MPa. The ultimate tensile strength increased approximately65.8%. The standard tensile specimens’elongation was from the DCC ingot’s20.2%to the EMCC ingot’s30.7%, which increased approximately44.8%. Simultaneously, the IF electromagnetic field can also decrease the segregation degree of the high purity Al-1%Si ingots. In terms of macro-segregation, the electromagnetic field made the solute Si element evenly distribute in the whole ingots; In micro-segregation, it made the eutectic Si become the uniform distribution on the refine boundaries and in the refine grains from the gathered distribution on the coarse boundaries. The IF electromagnetic field increased the solubility of Si element in the α-Al matrix, from the DCC ingot’s0.40%(mass fraction) to the EMCC ingot’s0.47%. The segregation degree of solute Si element was suppressed.With the different intensity of pulse electromagnetic field handling the Al-1%Si alloy melt, a periodic pulse oscillation generated by the pulse electromagnetic field was used to homogenize the temperature and solute field of Al-1%Si alloy melt. At the same time, it can also make lots of nuclei drift from the mold wall to the alloy melt to increase the nucleation rate, while the Al-1%Si alloy melt was solidification. Finally, the solidification structure of ingots was refined and improved. The results suggested that, when the geometric size of ingots was small, the discipline of refining solidification structure by the pulse electromagnetic field was firstly refining, secondly coarsening, then again refining with the pulse excitation current increasing. Meanwhile, the pulse electromagnetic field can also influence the solute Si segregation degree and the morphology of the eutectic Si. The pulse electromagnetic field can suppress the degree of eutectic Si aggregation on the boundaries. With the pulse excitation current increasing, the degree gradually decreased, the solubility of Si slowly increased in the α-Al matrix, and the morphology of eutectic Si gradually changed from the elongate strip to the small block.