Activation energies of grain growth mechanisms in aluminum coatings

To produce a specific grain size in metallic coatings requires precise control of the time at temperature during the deposition process. Aluminum coatings are deposited using electron-beam evaporation onto heated substrate surfaces of both mica and lithium flouride. The grain size of the coating is determined upon examination of the microstructure in plan view and cross-section. Ideal grain growth is observed over the entire experimental range of temperature examined from 413 to 843 K. A transition in the activation energy for grain growth from 0.87 to 2.04 eV atom-1 is observed as the temperature increases from < 526 K to > 588 K. The transition is indicative of the dominant mechanism for grain growth shifting with increasing temperature from grain boundary to lattice diffusion