强磁场下保温时间对Fe-0.76%C钢先共析铁素体组织形貌的影响

 借助于光学显微镜研究了磁场（12 T）对Fe 0.76%C合金在807 ℃奥氏体化保温不同时间(10 min、30 min、60 min)后以2 ℃/min的冷速冷却后,先共析铁素体显微组织的形貌变化。结果表明：在相同奥氏体化保温时间下，经强磁场热处理样品的先共析铁素体的面积分数和晶粒数量明显高于无磁场热处理样品。这可归结为强磁场降低了先共析铁素体形核所需的驱动力。随着奥氏体化保温时间的延长先共析铁素体晶粒沿着强磁场方向伸长的趋势明显变弱。这主要是由于奥氏体晶粒随着奥氏体化保温时间的延长逐渐增大，导致铁素体晶核之间的距离增大，从而造成奥氏体中的Fe原子向先共析铁素体晶粒扩散的距离增大所致。

Effect of Holding Time on Microstructure of Proeutectoid Ferrite in Fe-0.76%C Alloy in High Magnetic Field

The microstructure of proeutectoid ferrite transformed from austenite in Fe 076%C alloy after holding at 807 ℃ in magnetic field(12 T).It was found that the amount and grain number of proeutectoid ferrite in the steel treated in magnetic field were more than that treated without magnetic field.It is assumed that the magnetic field decreased the driving force of proeutectoid ferrite nucleation. The proeutectoid ferrite grains elongated along the magnetic field direction, and the angles between the major axis of proeutectoid ferrite and magnetic field direction decreased with the increase of holding time.It is because austenite grains in the sample grew with the holding time, and the distance between the nuclei of proeutectoid ferrite became larger, leading to increase of diffusion distance of Fe atom from austenite to proeutectoid ferrite.