Why L12 intermetallics are brittle and how to make them ductile

Origins of the intrinsic and extrinsic brittleness of L12 intermetallics are analyzed. It is shown that the intrinsic behavior is determined by the dislocation process in the alloy, and that the extrinsic behavior is related to moisture-induced embrittlement. Converting DO22 structure to L12 structure does not necessarily yield a ductile alloy. To improve the intrinsic ductility, the alloying element must be able to change the bonding nature so that the glissile complex stacking fault-coupled dissociation of superdislocations is promoted, while an improvement in the extrinsic ductility might be achieved by partially replacing the light element in the alloy with a heavier alloying element.