annealing.) 6.Discuss the role of stacking fault energy in the microstructural and mechanical-property changes which result from the cold working of an annealed alloy and from the recovery of a cold-working alloy. 7.The catalyst in an automotive exhaust system consists of many very fine particles (10nm diam.)of metal (Pt)on a ceramic (alumina)substrate.The fineness is necessary to provide the maximum surface area per unit volume of precious metal. A dominant mechanism of deterioration for such a catalyst is the coarsening of these particles.This process parallels Ostwald ripening in solids. Discuss,with approximate equations,how the rate of coarsening would depend on:surface tension,surface diffusion coefficient,concentration of absorbed metal atoms,and temperature. 8.A metal-forming operation involves the compression of a cylinder of a fec metal to give a 50%reduction in height.(At room temperature the flow stress of the fcc metals shows little strain rate sensitivity.)This operation is done at room temperature where dynamic recovery occurs.At both temperatures the compression is done at several different strain rates with the max.and min.rates differing by an order of magnitude. (a)On a plot of load vs.strain rate show how the max.load required for the compression varies with strain rate.Show the plot for room temperature and elevated temperature on the same graph. (b)How would you expect the microstructure to differ for samples done at the two temperatures?The examination is made with a TEM using samples deformed at the slowest strain rate. (c)What would you see in the microstructure that would indicate the sample had undergone dynamic recrystallization instead of dynamic recovery? 9 (a)Define,using words and any figures you find appropriate,the following qualifying words as applied to continuum material behavior.For example,a material model may be called"rigid plastic."For each word of this type,show the meaning clearly. rigid visco-elastic visco-plastic anelastic elastic plastic ideal plastic (b)Discuss which kinds of laws listed in part (a)would be most appropriate for each of the following continuum analysis problems and why.Include in your material description only the most important effect:that is,the ones that are essential to a reasonably accurate solution. 1)Forming of an automobile fender from plain-carbon steel at room temperature. 2)Hot rolling of aluminum slabs. 3)Analysis of buckling initiation in vertical support columns. 4)Interaction energies between separated dislocations in a single crystal.annealing.) 6. Discuss the role of stacking fault energy in the microstructural and mechanical-property changes which result from the cold working of an annealed alloy and from the recovery of a cold-working alloy. 7. The catalyst in an automotive exhaust system consists of many very fine particles (10nm diam.) of metal (Pt) on a ceramic (alumina) substrate. The fineness is necessary to provide the maximum surface area per unit volume of precious metal. A dominant mechanism of deterioration for such a catalyst is the coarsening of these particles. This process parallels Ostwald ripening in solids. Discuss, with approximate equations, how the rate of coarsening would depend on: surface tension, surface diffusion coefficient , concentration of absorbed metal atoms, and temperature. 8. A metal-forming operation involves the compression of a cylinder of a fcc metal to give a 50% reduction in height. (At room temperature the flow stress of the fcc metals shows little strain rate sensitivity.) This operation is done at room temperature where dynamic recovery occurs. At both temperatures the compression is done at several different strain rates with the max. and min. rates differing by an order of magnitude. (a) On a plot of load vs. strain rate show how the max. load required for the compression varies with strain rate. Show the plot for room temperature and elevated temperature on the same graph. (b) How would you expect the microstructure to differ for samples done at the two temperatures? The examination is made with a TEM using samples deformed at the slowest strain rate. (c) What would you see in the microstructure that would indicate the sample had undergone dynamic recrystallization instead of dynamic recovery? 9 (a) Define, using words and any figures you find appropriate, the following qualifying words as applied to continuum material behavior. For example, a material model may be called “rigid plastic.” For each word of this type, show the meaning clearly. rigid visco-elastic visco-plastic anelastic elastic plastic ideal plastic (b) Discuss which kinds of laws listed in part (a) would be most appropriate for each of the following continuum analysis problems and why. Include in your material description only the most important effect: that is, the ones that are essential to a reasonably accurate solution. 1) Forming of an automobile fender from plain-carbon steel at room temperature. 2) Hot rolling of aluminum slabs. 3) Analysis of buckling initiation in vertical support columns. 4) Interaction energies between separated dislocations in a single crystal