Consider the most conventional 2D phase diagram where temperature is plotted along the y axis and composition of carbon along the x axis. Phases are mapped on the phase diagram if they are thermodynamically stable at some (x,y). but between 1044K(curie temperature) and 1185K paramagnetic beta phase is more stable than ferromagnetic aplha phase.
http://www.calphad.com/graphs/Metastable%20Fe-C%20Phase%20Diagram.gif
Dear Sushrut Marathe and Alexander B. Missyul’
Please go through the article 'The β Iron Controversy Revisited' by Prof. Laughlin, appeared in Journal of Phase Equilibria and Diffusion (39 (2018) 274-279).
Regards
Ajeet
Dear Sushrut,
The term "β-iron" for the paramagnetic phase is obsolete nowadays. Both ferromagnetic and paramagnetic phases are called α-iron as they have the same crystal structure and differ only in the magnetic ordering.
Even more, S.K. Saxena et al. (Science, Vol. 260, pp. 1312-1314 DOI: 10.1126/science.260.5112.1312; Science, Vol. 269, pp. 1703-1704 DOI: 10.1126/science.269.5231.1703) proposed to use "β-iron" for the metastable high-pressure phase of iron.
beta phase is not a separate phase for Fe... it is actually non-magnetic alpha phase which is also called as beta phase...
Beta ferrite is crystallographically identical to alpha ferrite, except for magnetic domains. Hence no need to mention seperately
- The alpha iron which exist between 768 to 910 o C is paramagnetic in nature is called beta iron, just it is non magnetic in nature while iron- iron carbide is drawn for temp v/s wt % carbon so no need to show magnetic nature of aplha iron.
Dear Sushrut Marathe and Alexander B. Missyul’
Please go through the article 'The β Iron Controversy Revisited' by Prof. Laughlin, appeared in Journal of Phase Equilibria and Diffusion (39 (2018) 274-279).
Regards
Ajeet
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