Body-centered-cubic iron developed an elastic instability, driven by spin fluctuations, near the α-γ phase transition temperature, Tc, of 912C that was associated with the dramatic reduction of the shear stiffness constant c’ = (c11-c12)/2 near Tc. This reduction of c’ has a profound effect upon the temperature dependence of the anisotropic elastic self-energies of dislocations in iron. It also affected the relative stability of the a<100> and a/2<111> prismatic edge dislocation loops formed during irradiation. The difference between the anisotropic elastic free energies provided the fundamental explanation for the observed dominant occurrence of the a<100>, as opposed to the a/2<111>, Burgers vector configurations of prismatic dislocation loops in iron and iron-based alloys at high temperatures.

Effect of the α-γ Phase Transition on the Stability of Dislocation Loops in BCC Iron. S.L.Dudarev, R.Bullough, P.M.Derlet: Physical Review Letters, 2008, 100[13], 135503 (4pp)