a) What are definitions of vacancy, interstitial, dislocation and interfacial defects?

b) Draw the structure of vacancy (in alloy), interstitial (in alloy), dislocation and interfacial (grain boundry) defects and define the important terms on the figure.

c) Rank the magnitudes of the diffusion coefficients from greatest to least for the following systems and explain the reason of your ranking:

N in Fe at 700C

Cr in Fe at 700C

N in Fe at 900C

Cr in Fe at 900C

Note: Both Fe and Cr have the BCC crystal structure, and the atomic radii for Fe, Cr, and N are 0.124, 0.125, and 0.065 nm