a) The atoms on the surface are more reactive than the atoms in the grain bounda

Question

a) The atoms on the surface are more reactive than the atoms in the grain boundaries. b) The diffusion coefficient of hydrogen atom in fcc iron is higher than that in bcc iron. _ c) The activation energy to produce vacancies increase with increasing temperature. _ d) The driving force for diffusion is concentration gradient. -e) Dislocations could be completely removed from crystals by special cooling techniques. f) fcc metals have higher tendencies to dissolve in each other compared to the tendency of bcc metals to dissolve in each other. _ g) Movement of dislocations are easier in metals compared to ceramics. h) The self diffusion of iron is easier than that of aluminium. i) The modulus of elasticity of iron is higher than that of aluminium.

Explanation / Answer

True and false statements

a) Atoms on the surface are more reactive than atoms in the grain boundaries : False

b) The diffusion coefficient of hydrogen atom in fcc iron is higher than that in bcc iron : False

c) The activation energy to produce vacancies increase with incresing temperature : False

d) The driving force for diffusion is concentration gradient : True

e) Dislocations can be completely removed from crystals by special cooling techniques : True

f) fcc metals have higher tendencies to dissolve in each other compared to the tendencies of bcc metal to dissolve in each other : True

g) Movement of dislocations are easier in metals compared to ceramics : True

h) The self diffusion of iron is easier than that of aluminium : True

i) The modulus of elasticity of iron is higher than that of aluminium : True

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