Comment on ‘‘Nucleated and continuous ordering inCu3Au’’

In a recent Letter by Ludwig et al.$ sup 1— the early-stage ordering kinetics in ${\mathrm{Cu}}_3$Au were studied. For samples quenched from a disordered state to temperatures just below the order-disorder transition, it was shown that within the resolution of the experiment, the short-range-order diffuse intensity near the (100) superlattice point initially relaxed in a manner consistent with the predictions of (linear) spinodal ordering theory${;}^2$ the corresponding spinodal temperature (${\mathit{T}}_{\mathrm{sp}}$) was found to be ΔT=${\mathit{T}}_{\mathrm{tr}}$-${\mathit{T}}_{\mathrm{sp}}$=34 K below the order-disorder transition temperature (${\mathit{T}}_{\mathrm{tr}}$) of 663 K, in good agreement with the value measured by Chen, Cohen, and ${\mathrm{Ghosh}}^3$ of ΔT=24.2 K.