broadening techniques to calculate LRO parameters, domain

size, and microstrains in similarly aged material. Their

conclusions support those of Chakravarti et al. (1970).

 Das and Thomas (1974) used TEM to study ordering at

650 C. After eight hours at 650 C they found diffraction

evidence for the existence of Ni2Mo and Ni4Mo. They

explain the presence of Ni2Mo as being due to

nonconservative antiphase boundaries on (420) planes of

Ni4Mo. The regions of APB thus formed correspond to small

ordered regions of Ni2Mo within the Ni4Mo ordered layers.

Above 650 C, there was no evidence of Ni2Mo

precipitation. Only Ni4Mo precipitated.

 Ni-25% Mo. Yamamoto et al. (1970) were the first to

study the structural changes during aging of a

stoichiometric Ni3Mo binary alloy rapidly quenched from

1100 C. At 860 C, both Ni2Mo and Ni4Mo precipitate from

the disordered matrix. These phases are subsequently

consumed by the growth of the ordered orthorhombic Ni3Mo

phase which nucleates at grain boundaries. Following this

work, Das and Thomas (1974) aged a quenched stoichiometric

Ni3Mo alloy at 650 C. They hoped, by aging at this lower

temperature, to reduce the nucleation kinetics so that the

earlier stages of decomposition (which were presumably

missed in the work of Yamamoto et al.) could be studied.

They confirm the results of Yamamoto et al. (1970), i.e.,

the presence of both Ni2Mo and Ni4Mo during the initial