Tensile behaviour of two DO3-ordered alloys: Fe3Si and Fe-20 at % Al-5 at % Si

The tensile behaviour, including fracture modes and deformation substructures, of two powder-produced DO₃-ordered alloys having compositions Fe-25 at % Si (Fe₃Si) and Fe-20 at % Al-5 at % Si, has been investigated from room temperature to 800° C. The brittle-to-ductile transition temperature for the Fe₃Si alloy occurred at a temperature between 500 and 550° C, while that of the Fe-20 at % Al-5 at % Si alloy was approximately room temperature. In both alloys fracture occurred by transgranular cleavage at room temperature, with the occurrence of an increasing proportion of intergranular cavitation with increasing temperature. At low strains plastic deformation occurred chiefly by movement of perfect superlattice dislocations which, with increasing strain, dissociated to produce next-nearest-neighbour antiphase boundary trails.