The shapes of coherent misfitting ${\mathrm{Ni}}_3$Al precipitates were systematically investigated using a parameter ζ defined essentially by the ratio of particle sizes along 〈100〉 and 〈110〉. The variation of ζ with size was measured in several alloys using electron microscopy. ζ does not depend uniquely on particle size; it is also strongly influenced by the volume fraction of ${\mathrm{Ni}}_3$Al. These results provide the first quantitative evidence that elastic interaction energy plays a major role not only in spatial correlations, but also in the morphological evolution of individual particles.

• Received 3 December 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.2305