Anomalous grain growth in commercial lead

Grain growth in commercial lead specimens with dimensions of 10 x 10 x 3 mm/sup 3/ was studied in a vacuum of 1.3 mPa (10 /sup -5/torr) at 448, 473, 498 and 532 K for various durations of time in the range 15 to 60 minutes. The main metallic impurity in commercial lead was 1.07 at% Sn. The relation between square of the mean rain-diameter, D/sup 2/, and annealing time, t, was undulatory, and is not explicable within the framework of existing models of normal grain-growth. The height of the peak observed at t=15 min in the D/sup 2/-t curve decreases as annealing temperature is increased from 448 to 523 K. The undulation in the D/sup 2/, isotherms arises probably due to rather high mobility of Sn atoms, intervention of occluded gases and voids, geometrical constraints due to specimen thickness etc. (author)