$30\_$Marks

$1\mathrm{.}1$ Briefly explain the relevance of line defects in the context of plastic deformation of

metals. $(3)$

$1\mathrm{.}2$ Use appropriate mathematical equation, and briefly explain why is $[110]$ slip direction

preferable in FCC materials $(3).$

$1\mathrm{.}3$ Other than planar density, why is the family of $\{111\}$ preferred over $\{110\}$ planes in

FCC material during plastic deformation of metals, you need to justify your answer by

means of a calculation. $(6)$

$1\mathrm{.}4$ Why are FCC materials easily deformable as compared to BCC materials? $(6)$

$1\mathrm{.}5$ BCC materials are difficult to deform at room temperature and as result the temperature

must be raised so that they can be deform easily. Explain the reasoning behind this

statement. $(3)$

$1\mathrm{.}6$ In polycrystalline material, during application of stress the grains tend not deform

simultaneously, explain why is this possible and how do non$-$deforming grains interact

with the deforming grain to avoid fracture. $(4)$

$1\mathrm{.}7$ Derive an equation to calculate the normal stress acting perpendicular to the slip plane

during application of tensile force $(P)$ in a single crystal. $(5)$