Growth by Ledges

The prediction and observation of growth ledges at various moving interphase boundaries in solid-solid phase transformations has become increasingly widespread since first proposed in the early 1960's by Aaronson. The role of steps at the growth interfaces in several phase transformations is reviewed. For precipitate plates emphasis is placed on rationalizing experimental growth kinetics with mathematical models developed for the migration rate of a ledge. More complex transformations are employed to examine the possible role of growth ledges to account for microstructure development. In all cases, the growth ledge is shown to be necessary to fully understand solid-solid phase transformations.