An investigate was made of how the observed strong variation of elastic constants as functions of temperature affects the strength of interactions between dislocations, and mechanisms of plastic deformation of iron at elevated temperatures. It was found that the observed severe softening of the tetragonal shear modulus C′ at high temperature gives rise to a drastic reduction in the repulsion between parallel like edge dislocations, and hence to a greatly increased number of dislocations in pile-ups, especially those in the <100>(001) configuration. The associated increase in plastic strain will lead in turn to a conspicuous reduction in tensile strength as C′ falls. The phenomenon was inherently anisotropic, and this work underlines the importance of including anisotropic elastic effects when modelling Fe at high temperatures.

Interaction between Dislocations in BCC Iron at High Temperature. S.P.Fitzgerald, S.L.Dudarev: Journal of Nuclear Materials, 2009, 386-388, 67-70