Ordering transformations in Ni₇₅Mo₁₅Mn₁₀ alloy

摘要

Effect of partial substitution of Mo in Ni₃Mo by Mn on its ordering behaviour is studied here using Transmission Electron Microscopy (TEM). The change in alloy composition does not change the nature of the short range ordered (SRO) state, which shows intensity maxima at {1½ 0} and equivalent positions. However, prolonged aging at 973 K leads to transformation of the Ni₇₅Mo₁₅Mn₁₀ alloy, studied here, almost entirely into the ordered D0₂₂ phase unlike in the case of the binary Ni-Mo alloy. Curved antiphase boundaries (APBs), with wetting of the interdomain D0₂₂ regions by the disordered phase, characterize the microstructure of the aged alloy. A small volume fraction of a sigma-like topologically close packed (TCP) phase that appears in the as quenched alloy seems to remain unaffected by ageing.