Plastic deformation in Fe-Si alloys

A detailed study has been made of the compressive stress-strain behavior of polycrystal-line Fe-Si alloys containing from 0 to 25 at. pct Si. It is shown that the alloys containing less than 10 at. pct Si possess only short range atomic order and deform by slip or by twinning, depending upon temperature. At concentrations greater than 10 at. pct Si, the alloys possess long range atomic order. Deformation twinning is suppressed in this region, and the deformation occurs entirely by slip. Deformation by slip may occur either by the motion of perfect superlattice dislocations, or else by the movement of imperfect superlattice dislocations, with the subsequent generation of antiphase boundaries. The type of superlattice dislocation that prevails depends upon a critical combination of both composition and temperature.