Antiphase Domains, Disordered Films and the Ductility of Ordered Alloys Based on Ni3Ai

Abstract

AbstractIn elements and intermetallic compounds alike, tensile ductility is favoured by a small spacing of obstacles to dislocation movement, whether these obstacles be grain boundaries or other structural features. The evidence for this generalisation is reviewed.Antiphase domains (APD) form only when Tt is below the freezing temperature, Tf: this isa rule which has not hitherto been recognized. In Ni-Al, Tt < Tf when the Al content is less than ≈23.5at.%. APD's can serve as heterogeneous nuclei where films of disordered (γ) phase deposit. Domains, especially if decorated by γ films, are associated with enhanced ductility, and there is circumstantial evidence that the ductility is indeed caused by these microstructural features.