Quiz2A_MSEG302 - D o a ll P roblems (10 11100 otal P oints)...

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(1 011100 Total Points) Write your answers required use the resides. QUIZ#2a MSEG 302 Name: below the question on this paper. lf extra room is back of the page on which a specific question 8-1 (15 pts) Explain the three stages of annealing of metallic materials. , 1. *;" t.- trr, Recovery: A low.temperature treatment that removes the residual stresses due to cold working without causing a change in dislocation density. The original cold-worked microstructure is composed of deformed grains containing a large number of tangled dislocations. When the metal is first heated, the additional thermal energy permits the dislocations to move and form the boundaries of a polygonaized subgrain structure. Recrystalli zatson: A medium-temperature annealing heat treatment rapid recovery eliminates residual stresses and produces the polygonized dislocation structure. New small grains then nucleate at the cell boundaries of the polygonized structure, eliminating most of the dislocations. Because the number of dislocations is greatly reduced, the recrystallizatedmetal has low strength but high ductility. Grain Growth: A higher-temperature annealing heat treatment, both recovery and recrystallization occur rapidly, producing a fine recrystallized grain structure. If the temperature is high enough, the grains begin to grow, with favored grains consuming the smaller grains. (a) (c) (d) Figure 8'16 The effect of annealing temperature on.the microstructure of cold-worked metals. (a)
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This note was uploaded on 02/01/2012 for the course MSEG 302 taught by Professor Snively during the Spring '08 term at University of Delaware.

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Quiz2A_MSEG302 - D o a ll P roblems (10 11100 otal P oints)...

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