Analysis of Split Patterns in ?-?' Ni Alloys

Abstract

AbstractPairs of ?' particles in different Ni base alloys are investigated in order to determine the mechanism responsible for the formation of several particle arrays. Special attention is given to symmetrically arranged particles or the split patterns i.e., they have been believed to result from the splitting of large particles. High resolution electron microscopy is used to determine the translation domains of coherent ?' particles. The [001] zone axis allows determination of all possible translations due to differently nucleated domains. About 72 % of particle pairs forming splitting configurations are in the out-of-phase relationship (different translation order domains), indicating that most adjacent pairs are not formed by the splitting of a large particle. On the other hand, particles in symmetrical array (quartets) always have at least one particle with a different translation order domain. Additionally, the frequency of out-of-phase pairs is 78 % in quartet configurations. Calculation of probabilities shows that the quartet split patterns are not formed by splitting but most likely by means of migration due to diffusion.