HW 5-Sol - HW 5- Solution Self-diffusion is atomic...

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HW 5- Solution Self-diffusion is atomic migration in pure metals--i.e., when all atoms exchanging positions are of the same type. Interdiffusion: diffusion of atoms of one metal into another metal. Vacancy diffusion: diffusion of atoms into a neighboring empty space. Note that self-diffusion is mediated normally by vacancy diffusion. Interdiffusion is usually mediated by vacancy diffusion in substitutional alloys. (a) With vacancy diffusion, atomic motion is from one lattice site to an adjacent vacancy. Self-diffusion and the diffusion of substitutional impurities proceed via this mechanism. On the other hand, atomic motion is from interstitial site to adjacent interstitial site for the interstitial diffusion mechanism. (b) Interstitial diffusion is normally more rapid than vacancy diffusion because: (1) interstitial atoms, being smaller, are more mobile; (2) the probability of an empty adjacent interstitial site is greater than for a vacancy adjacent to a host (or substitutional impurity) atom; (3) strain on the host lattice is usually smaller in the case of interstitial diffusion.
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HW 5-Sol - HW 5- Solution Self-diffusion is atomic...

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