Relationship between the APD structure and ductility of rapidly solidified Ni₃Al alloys

Rapidly solidified Ni₃Al ribbons and wires are prepared to examine the relationship between antiphase domain (APD) structure and ductility. As-rapidly solidified ribbons of Ni-rich binary and ternary Ni₃Al alloys show fine APD structure and exhibit no ductility, except for Ni-22A1-20Co. The ribbons annealed at temperatures higher than 1173 K, however, become ductile, although annihilation of APDs and grain growth occur. This indicates that ductility of Ni₃Al ribbons is not directly related to APD structure but is determined by alloy composition. Melt-spun Ni₃Al wires consist of a dendritic structure as usually seen in conventional castings, suggesting that the cooling rate during solidification of molten stream is not so high as to suppress the development of dendrites. It is found that the microstructure of the melt-spun Ni₃Al wires is quite different from that of the rapidly solidified Ni₃Al ribbons.