In [2]:

```
from __future__ import division
from math import sqrt
#given
#atomic radiii of gamma-iron having FCC lattice
rFCC=1.26 #A
#atomic radius of alpha-iron having BCC lattica
rBCC=1.24 #A
#as we know that FCC and BCC has effective no of atoms 4 and 2 resp
#so
aBCC=4/sqrt(3)*rBCC #A
aFCC=2*sqrt(2)*rFCC #A
#volume of lattice for FCC and BCC
VFCC=(aFCC)**3 #A**3
VBCC=(aBCC)**3 #A**3
#percentage change in volume during phase transformation of gamma-iron to alpha-iron is given by
percent_vol_change=(VFCC/4-VBCC/2)/(VFCC/4)*100
print "the percentage volume change during phase transformation of gamma-iron to alpha-iron is %0.3f"%(percent_vol_change)
```

In [3]:

```
from __future__ import division
#given
#young's modulus
E=51*10**9 #Pa
#poisson's ratio
nu=0.22
#magnitude of burger's vector
b=2*10**-10 #m
#we know that shear modulus is given by
G=E/2/(1-nu) #Pa
#elastic strain energy of dislocation in cold worked tin
Ue=1/2*G*b**2*10**12 #Pa m
#the strain energy in tin before cold working may be neglected as it is smaller by three orders of magnitude.
print " the change in energy during recrystallization is %0.3f Pa m"%(Ue)
```