Effect of High Magnetic Field on Phase Transformation Temperature in Fe-C Alloys

Magnetic field can affect the transformation temperature and microstructure if a transformed phase has different susceptibility with parent phase. Fe-C alloy is an ideal system to show the magnetic field effect since in this system, austenite (fcc structure) is a paramagnetic phase and ferrite (bcc structure) is a ferromagnetic phase below 770°C. In this paper, phase transformation temperature in Fe-C alloys in a magnetic field was measured from cooling curve. It was found that the transformation temperature for pure Fe from austenite to ferrite has a linear relationship with magnetic field strength, increasing about 0.8°C per unit of magnetic field of 1 T. For eutectoid transformation in Fe-0.8C alloy, similar relationship exists, the transformation temperature increases about 1.5°C per unit of magnetic field of 1 T. Experimental results do not agree well with that calculated by molecular field theory. An elongated and aligned microstructure by transformation in a high magnetic field was found in an Fe-0.4C alloy, but was not found in pure Fe and Fe-0.8C alloy.