Al-0.5%Cu-1%Si thin films deposited onto oxidized Si substrates were subjected to both wafer curvature and in situ transmission electron microscopy thermal cycling experiments between room temperature and 450C. The evolution of precipitates was monitored during cycling. Chemical analysis revealed that the precipitates were pure Si. Their average size increased from 80nm in the as-deposited state to 300nm after thermal cycling. The Si precipitates serve as anchoring points for dislocations and grain boundaries. Direct evidence for pipe-diffusion ripening was found in the vicinity of a dissolving precipitate. Real-time measurement of the radius of the precipitate permitted the estimation of the coefficient of pipe diffusion of Si in Al at this temperature. As expected, this coefficient was several orders of magnitude larger than the volume diffusion coefficient.

Pipe-Diffusion Ripening of Si Precipitates in Al-0.5%Cu-1%Si Thin Films. M.Legros, B.Kaouache, P.Gergaud, O.Thomas, G.Dehm, T.J.Balk, E.Arzt: Philosophical Magazine, 2005, 85[30], 3541-52