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Diffusion in aluminium alloys, Hot deformation (rolling) of aluminium alloys and its dynamic recovery, dynamic recrystallisation
Engineering and Construction
Pages 10 (2510 words)
Chapter 2: Literature Review: Diffusion of Aluminum alloys 2.1 Diffusion Diffusion or the movement of solute particles from high concentration to low concentration in order to obtain an equilibrium and even spread forms the basic mechanism through which processes like homogenization, solution and aging occur.
The activation energy and diffusion constants are calculated using a variety of factors like the solid solubility, alloying content and the state of the matrix microstructure in terms of grain boundary size, dislocation density and vacancy concentration [PAPM]. The mean distance travelled by the atom during diffusion in turn is dependent on the rate of diffusion D as follows: L = (Dt)? Where L = the mean distance travelled by the atom. t = time (s) All atoms above absolute zero (-273oC) vibrate and the frequency of vibrations acts as the driving force for the movement of the atoms or for their diffusion. The frequency of vibration and diffusion increases with the rise in temperature. However, for atoms to be able to move from one lattice point to the other, the atoms need to overcome the activation energy. This activation energy is low around the metal surface and at the grain boundaries, and this is the reason for the high concentration of the precipitating solute at the grain boundaries. ...
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