Ferrite Transformation from Fe-0.3N Austenite

Ferrite transformation behavior of Fe-0.3 mass%N binary alloy was studied in the temperature range between 500 degrees C and 750 degrees C. By isothermal holding in the alpha + gamma two phase region, two morphologies of Allotoriomorphic ferrite (AF) and Widmanstetten ferrite (WF) formed from the prior gamma grain boundary. On the other hand, in the case of isothermal holding at 500 degrees C, nitride-free bainitic ferrite (BF) was formed at the beginning, and changed to bainite accompanied with gamma' precipitation in further holding. The retained gamma was obtained by decreasing the transformation temperature in the two phase region, and maximum volume fraction of 9% was obtained at 600 degrees C. AF had near K-S OR with one side of the adjacent prior gamma and grew into the grain without K-S OR. On the other hand, WF and BF had near K-S relationship with the matrix. Both WF and BF had significantly higher energy dissipation than AF, and the energy dissipation of AF is due to interfacial friction. On the other hand, the strain energy associated with the transformation was dominant in WE

Automated summary

The ferrite transformation behavior of the Fe-0.3 mass%N binary alloy was studied, revealing the formation of different morphologies of ferrite at different temperatures and investigating the growth mechanisms and energy dissipation of different types of ferrite.