8 Consider the transformationy>+y taking place in an Fe-C alloy such that nuclei of a form only on y/y grain boundaries;nucleation is complete in a very short time;the a particles thicken and also grow along the boundaries;eventually all the prior boundaries become slabs of a that continue to thicken.How would you predict the fraction transformed with time in this case? 9. The local curvature of the liquid-solid interface has a direct thermodynamic effect (e.g.,through the Gibbs-Thomson coefficient)on the thermal field associated with the solidifying system.In many theoretical and experimental solidification cases it is desirable to work with a planar or flat liquid-solid interface. (a)Describe and discuss the solidification conditions required to obtain a planar liquid-solid interface with an alloy which solidifies as a single phase binary solid solution.If you use equations to formulate the criteria for planar liquid-solid interfaces,define all the symbols used in the equations. (b)Discuss how the conditions for the formation of a planar liquid-solid interface are similar different with respect to your answer in part (a) for the solidification of a binary eutectic alloy. 10. Considering both the initiation and the growth stages,describe the principal characteristics of discontinuous precipitation reactions and discuss their significance with respect to theoretical descriptions of the reactions. 11.For the growth of NiO scale upon the oxidation of nickel: (a)Why have investigators claimed that grain boundary Ni diffusion is significant? (b)By what mechanism(s)can cation vacancies be eliminated at the metal/scale interface? (c)Why should Li impurities reduce the scaling rate,while Cr impurities increase the rate? (d)What data do you need to predict the high temperature parabolic rate constant by the Wagner theory? (e)How would the oxidation characteristics change for an alloy of 80Au-20Ni? (f)The scale NiO is very susceptible to acid fluxing in hot corrosion by a Na2SC4 condensate.Explain the problem/mechanism. 12.(a)What are ternary eutectic and peritectic reactions? (b)Consider the hypothetical ternary system A-B-C shown below and8. Consider the transformationγ → + α γ taking place in an Fe-C alloy such that nuclei of a form only on γ / γ grain boundaries; nucleation is complete in a very short time; the a particles thicken and also grow along the boundaries; eventually all the prior boundaries become slabs of a that continue to thicken. How would you predict the fraction transformed with time in this case? 9. The local curvature of the liquid-solid interface has a direct thermodynamic effect (e.g., through the Gibbs-Thomson coefficient) on the thermal field associated with the solidifying system. In many theoretical and experimental solidification cases it is desirable to work with a planar or flat liquid-solid interface. (a) Describe and discuss the solidification conditions required to obtain a planar liquid-solid interface with an alloy which solidifies as a single phase binary solid solution. If you use equations to formulate the criteria for planar liquid-solid interfaces, define all the symbols used in the equations. (b) Discuss how the conditions for the formation of a planar liquid-solid interface are similar / different with respect to your answer in part (a) for the solidification of a binary eutectic alloy. 10. Considering both the initiation and the growth stages, describe the principal characteristics of discontinuous precipitation reactions and discuss their significance with respect to theoretical descriptions of the reactions. 11. For the growth of NiO scale upon the oxidation of nickel: (a) Why have investigators claimed that grain boundary Ni diffusion is significant? (b) By what mechanism(s) can cation vacancies be eliminated at the metal/scale interface? (c) Why should Li impurities reduce the scaling rate, while Cr impurities increase the rate? (d) What data do you need to predict the high temperature parabolic rate constant by the Wagner theory? (e) How would the oxidation characteristics change for an alloy of 80Au-20Ni? (f) The scale NiO is very susceptible to acid fluxing in hot corrosion by a Na2SC4 condensate. Explain the problem/mechanism. 12. (a) What are ternary eutectic and peritectic reactions? (b) Consider the hypothetical ternary system A-B-C shown below and