$2\mathrm{.}1$ What are the partial dislocations formed from $\frac{a}{2}[\frac{?}{\text{b}\text{a}\text{r}}\frac{1}{b}ar(1)0]$ on the $(\frac{?}{\text{b}\text{a}\text{r}}(1)\frac{1}{b}ar(1))$ in an FCC crystal

structure.

$2\mathrm{.}2$ Is the reaction in $2\mathrm{.}1$ energetically feasible?

Question $3-30$ Marks

$3\mathrm{.}1($Bonus$)$

The SFE for an FCC metal A was reduced from $200$ to $150mJ{m}^{-2}$ when it was alloyed

with a little amount of metal B$.$ The Burgers vector of the partials for an extended

dislocation in metal A and alloy $A-B$ also remained constant. Calculate the $\%$ change in

equilibrium spacing between partials due to alloying and comment on your answer.

Equilibrium separation $(d_s)=\frac{G{b}^2}{24}$

$3\mathrm{.}2$ A straight$-$line dislocation in copper has a Burgers vector parallel to $[110]$ direction and

the dislocation line is parallel to $[\frac{?}{\text{b}\text{a}\text{r}}(1)01]$ direction. Determine mathematically the slip plane

of the dislocation and draw it neatly in a unit cube.

$3\mathrm{.}3($Bonus$)$

A screw dislocation line gliding on plane $(\frac{?}{\text{b}\text{a}\text{r}}(1)11)$ will cross slip to plane $(1\frac{?}{\text{b}\text{a}\text{r}}(1)1)$ if it

encounters an obstacle during plastic deformation. Use algebra to find a common slip

direction $($zone axis$)$ between the two planes that will be used by the screw dislocation to

cross slip.