Experimental Study and Modelling on the Grain Growth of Annealing Process in Fe-50%Ni Alloy

Fe-50%Ni alloy is widely used in industrial fields as its excellent magnetic performance, and the average grain size has a strong effect on magnetic performance. In this paper, Fe-50%Ni alloy specimens are annealed under the hydrogen protection and vacuum respectively at different temperatures and holding times. Metallographic observation and grain size measurement are both finished. The metallographic observation shows that grains grow up more easily and fast under the hydrogen atmosphere than in vacuum. Hydrogen can reduce the chemical activation energy, and decrease the impurity elements more easily. A new model is proposed to describe the grain size basing on the assumption that \(\overline {{D^2}} - \overline {D_0^2} \alpha {t^m}\) by experiments and \(\overline {{D^2}} - \overline {D_0^2} \alpha {e^{ - \tfrac{Q}{{RT}}}}\) by thermo dynamical theory. The fitting result shows that the new model can describe the grains growth process better than the classical one.