Solidification Behavior And Optical Characterization Method, The Magnetic Field

Optic technique is applied widely in all fields, including material science. The solidification behavior can be gotten indirectly by using metallographic optic microscope and directly by using optic token methods. In other side, a lot of investigation results indicate that the rotating magnetic field (RMF) and static magnetic field (SMF) have significant effects on solidification process. These show a potential application of the RMF and SMF in industry. However, the detailed mechanisms of the RMF and SMF during melt solidification process are still unclear. More experimental and theoretical investigations are necessary to better understand the effect mechanisms. As a result, in this thesis, we use optic methods to study the solidification problems at several sides.In this work, Pb-Sn, Sn-Bi and Bi-In eutectic alloy systems are investigated by using the magnetic experiment instruments designed by us. The influence of the RMF and SMF on the solidification process of alloys is studied by comparing the solidification microstructures under the common condition and RMF, SMF conditions. Several optic methods are studied to observe melt solidification process directly. Important results are drawn as following.It is found that the RMF can completely eliminate the gravity-induced macrosegregation, result in dendrite fragmentation and promote solute diffusion velocity in Pb-Sn alloys. These differences are regarded as the effect of complicated melt flow caused by the RMF. Moreover, when the content of the primary phase (Pb) or (Sn) is small, many spherical microstructures form under the RMF condition. The analyses indicate that these special microstructures are likely the conjunction action of melt flow and concentration and temperature field uniformity caused by the RMF. The effect of the SMF on Pn-Sn alloys, however, is not evident.The investigation on Sn-Bi and Bi-In alloys strengthen the results that the RMF can completely eliminate the gravity-induced macrosegregation and result in dendrite fragmentation. And the results show that the RMF has the effect to increase cooling rate and promote nucleation of alloy melt. The comparisons indicate that the RMF has the same effect on dendrites formed by solid solution phases and intermetallic phases. But the RMF has little effect on (Bi) facet phase.The investigation shows that many optic methods are being applied in transparent crystal growth real time observation. Based on those methods and melt solidification characteristics, several optic methods to observe molten melt solidification process are designed.