Diffusional transformation in solids $(10$P$)$

a$.$ Write the four different energy terms involved in the calculation of the free energy change in heterogeneous nucleation in solids. $(2$p$)$

b$.$ List the sequence of various nucleation sites in order of increasing order of $G_d($free energy change due to defect destruction$).(($:$2p\}$

c$.$ List the structure and size range of GP Zone, ${}^{\text{'}\text{'}}($Theta Double Prime$),{}^{\text{'}}($Theta Prime$)$ and $($Theta$)$ which evolve during the aging process after solution treatment and quenching in $Al-4wt.\%Cu$ alloys. $(4$p$)$

d$.$ How does partitioning affect the growth of pearlite in $Fe-C$ alloys? $(2$p$)$

Diffusionless Martensitic Transformation $(10$P$)$

a$.$ Write at least six important features associated with martensitic transformation. $(3$p$)$

b$.$ What are the differences between lath and plate martensite with respect to morphology and formation temperature? $(2p$

c$.$ Martensitic transformation is diffusionless, i$.$e$.,$ the change in crystal structure is achieved by a homogeneous deformation of austenite. The strain needed was first proposed by Bain in $1924$ and is known as the "Bain strain". What is Bain strain? $(2$p$)$

d$.$ What is autotempering? What are the two factors that the first laths form are thicker than those forming at lower temperatures in autotempering? $(3$p$)$