CHARACTERIZATION OF A MASSIVE TRANSFORMATION BY MICROSTRUCTURAL ANALYSIS

Quantitative metallography was employed to investigate experimentally the nucleation behavior and growth rates in a quenched Ag + 50 at. pct Cd alloy undergoing an isothermal massive transformation at 373 K (10 0 degrees C). The experimental characterization of the massively trans forming microstructure as a function of time was accomplished by the s tereological measurement of the microstructural variables, V-nu, the v olume fraction transformed, S-nu, the parent/daughter interfacial area density, and lambda(max), the largest intercept-free nodule length of the newly forming daughter phase. These data were compared to statist ically derived geometrical models of the microstructure formulated on various nucleation and growth premises and expressed in terms of these same variables, A model was found which matched the data in all respe cts, and this allowed certain nucleation characteristics, the interfac e migration rates, and the nodule shapes of the daughter phase to be d educed.