Effects Of High Magnetic Field On Abnormal Microstructure Of High Purity Fe-1.1%C Alloys

In this work, High purity Fe-1.1%C alloy are selected and treated without and with a12T static magnetic field. The obtained microstructures are analyzed by optical microscopy and the evolution and formation mechanisms of the high purity Fe-C alloy under a high magnetic field are systematically studied.Magnetic field considerably affects the abnormal microstructure in Fe-1.1%C alloy. Magnetic field can increase the area fraction of abnormal microstructure in Fe-1.1%C alloy by remarkably decreasing the Gibbs energy needed for the ferrite transformation. Simultaneously, due to the fact that the Ae1line shifts to high temperature side with the increase of magnetic field intensity, the abnormal microstructure transformation has to stop and the pearlite transformation begins, therefore, the area fraction of abnormal microstructure firstly increase and then decrease with the increase of magnetic field intensity.When the normal direction of sample in Fe-1.1%C alloy is parallel to the field direction, the effective magnetic field intensity is lower than that in the case when the normal direction of a plate sample is perpendicular to the field direction, and the magnetic field intensity is enough(more than4T) to end the abnormal microstructure transformation, and make the pearlite transformation begin. Therefore, the area fraction of abnormal microstructure in the case when the normal direction of sample is parallel to the field direction is larger than that in the case when the normal direction of sample is perpendicular to the field direction.It is indicated that the macro-hardness of the sample is decreased when treated under high magnetic field, which can be ascribed to the following two factors. On the one hand, high magnetic field could increase the relative content of abnormal microstructure, which lowers the macro-hardness of the sample. On the other hand, pearlite space is increased after being treated under high magnetic field, and the larger the pearlite space is, the smaller the macro-hardness is, as pearlite space is the main factor of influencing the macro-hardness of the sample tested in this experiment.