Investigation of amorphous phase formation in Fe-Co-Si-B-P - Thermodynamic analysis and comparison between mechanical alloying and rapid solidification experiments

•Solid state amorphisation in different Fe-Co based alloys was investigated considering thermodynamic and kinetics requirements.•Amorphisation ability was evaluated for different elements added to Fe-Co alloy.•Satisfaction of thermodynamic and kinetics requirements does not guarantee the amorphisation by mechanical alloying.

In recent years, amorphous alloys have received a considerable attraction because of their physical, mechanical and magnetic properties. Fe-Co alloy system has good soft magnetic properties (high magnetic saturation and high Curie point) which makes it suitable for high temperature magnetic applications. In this paper, the effect of different elements on glass forming ability (GFA) of Fe-Co system was evaluated based on Meidema semi-empirical model and the results were compared to mechanical alloying (MA) experiments. Si, B and P seem to be good elements to be added to Fe-Co alloys with respect to thermodynamics and kinetics requirements. Calculations based on extended Miedema model showed that enthalpy and Gibbs free energy changes for solid state amorphisation of Fe70Co7Si8B8P7 were −179 (kJ mol−1) and −181 (kJ mol−1) respectively, but MA experiments in three different routes did not lead to amorphisation in this system. Also comparison between MA and melt spinning (MS) techniques showed GFA in both techniques are completely different.