Allotropic Forms of Iron

Iron has three allotropic forms of crystal at different temperature. It undergoes all the allotropic forms when it is heated  from normal temperature to high temperature (molten state).
1. Alpha Iron. It occurs from normal temperature to 910 degree centigrade and has got body-centered cubic (b.c.c.)lattice crystals.
(i) Ferromagnetic alpha iron which occurs from normal temperature to 770 degree centigrade.
(ii) Paramagnetic  alpha iron which occurs from 770 degree centigrade to 910 degree centigrade.
2. Gamma Iron. This occurs from 910 degree centigrade to 1400 degree centigrade, and has got crystal structure of face-centered cubic (f.c.c.) lattice.
3. Delta Iron. This occurs from 1400 degree centigrade to 1539 degree centigrade (molten state), and has got crystal structure of body-centered lattice.
 Pure Iron is soft and has got silvery white color.It is strongly magnetic in presence of a magnetic field or electric current. When inducing field is removed the induced magnetism is not retained by pure iron. This power of retentivity of magnetism of pure iron is improved by the addition of other elements such as carbon, cobalt, or nickel. Iron loses its magnetic properties when heated to 770 degree centigrade.