Transmission electron microscopy characterization of Al2Cu precipitate growth kinetics by in situ heat treatment

Growth kinetics of the Al2Cu (θ) precipitate in an Al–1.5Cu alloy thin film were characterized in situ using transmission electron microscopy (TEM). The sizes of θ precipitates during isothermal growth in TEM were measured during aging at 250, 275 and 300 °C. The results of precipitate growth were analyzed based on the model of the “collector plate mechanism” for bulk alloys. The lengthening of the θ precipitate in thin film varies as t0.29 for short annealing times (up to ∼10–20 min) at temperatures between 250 and 300 °C. This is in good agreement with the analysis in bulk alloys. For longer annealing time, however, the t0.29 time law does not fit as the distances of Cu volume diffusion exceed one half of the film thickness.