1.Use the concepts of classical nucleation theory to explain the following: (a)Homogeneous nucleation rarely occurs in solid-state transformations (b)Liquid metals can be easily supercooled but solid metals are difficult to super-heat at atomspheric pressure. (c)Metastable phases are often formed in solid state phase transformations. (d)Solid nuclei on substrates exposed to vapors can show epitaxial relationships (e)Homogeneous nucleation of liquid droplets from water vapor is easily accomplished in a cloud chamber whereas this is not true for the case of copper. 2.Describe with specific examples,the characteristics of the athermal martensitic transformation. 3.Suppose that you are attempting to device an experiment with the objective of testing homogeneous nucleation for continuous precipitation in a binary alloy.Discuss the problems you would expect to encounter in creating a successful experiment according to the possible observation techniques that might be used. 4. Describe,with the aid of diagrams,what you understand by a pure twist boundary and a pure tilt boundary.Emphasize in your answer what parameters can be used to define the boundary in each case,and what type of dislocations are they? 5.Write an essay entitled "Effects Upon Solid State Phase Transformations Due to Grain Boundaries." 6. A single phase solid solution alloy is to be solidified to obtain the following final microstructure: (a)a single crystal, (b) large equiaxed grains. (c)columnar grains, (d)extremely small equiaxed grains. Describe how you would control the solidification processing in order to produce each of the above four microstructures in a given nominal composition solid solution alloy.Clearly identify the solidification variables which you would control and,where possible,the quantitative values you would need for those variables to produce the various structure. 7 The theory of nucleation and growth kinetics(Johnson-Mehl-Avrami)is often applied to an a>B allotropic transformation by assuming nuclei to form randomly within a unit volume of bulk material and to grow as spheres at constant rates.How would you modify the theory to describe a similar transformation taking place in a very thin sheet?How would the time dependence change?1. Use the concepts of classical nucleation theory to explain the following: (a) Homogeneous nucleation rarely occurs in solid-state transformations. (b) Liquid metals can be easily supercooled but solid metals are difficult to super-heat at atomspheric pressure. (c) Metastable phases are often formed in solid state phase transformations. (d) Solid nuclei on substrates exposed to vapors can show epitaxial relationships (e) Homogeneous nucleation of liquid droplets from water vapor is easily accomplished in a cloud chamber whereas this is not true for the case of copper. 2. Describe with specific examples, the characteristics of the athermal martensitic transformation. 3. Suppose that you are attempting to device an experiment with the objective of testing homogeneous nucleation for continuous precipitation in a binary alloy. Discuss the problems you would expect to encounter in creating a successful experiment according to the possible observation techniques that might be used. 4. Describe, with the aid of diagrams, what you understand by a pure twist boundary and a pure tilt boundary. Emphasize in your answer what parameters can be used to define the boundary in each case, and what type of dislocations are they? 5. Write an essay entitled “Effects Upon Solid State Phase Transformations Due to Grain Boundaries.” 6. A single phase solid solution alloy is to be solidified to obtain the following final microstructure: (a) a single crystal, (b) large equiaxed grains, (c) columnar grains, (d) extremely small equiaxed grains. Describe how you would control the solidification processing in order to produce each of the above four microstructures in a given nominal composition solid solution alloy. Clearly identify the solidification variables which you would control and, where possible, the quantitative values you would need for those variables to produce the various structure. 7. The theory of nucleation and growth kinetics (Johnson-Mehl-Avrami) is often applied to an α → β allotropic transformation by assuming nuclei to form randomly within a unit volume of bulk material and to grow as spheres at constant rates. How would you modify the theory to describe a similar transformation taking place in a very thin sheet? How would the time dependence change?