Test 4 Study Guide - Test IV Study Guide Kinetics of Phase...

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Test IV Study Guide Kinetics of Phase Transformations 1. Strengthening Mechanisms a. Precipitation Hardening i. Hardening or strengthening of an alloy by the presence of a fine, uniformly distributed precipitate b. Solid Solution Strengthening i. Works by adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal) ii. The alloying element diffuses into the matrix, forming a solid solution c. Controlled Eutectic/Eutectoid Reactions d. Cold Working i. Process used to increase dislocation density by forcing the material to undergo plastic deformation e. Martensitic Transformations i. A shearlike transformation with no change in composition when the parent phase transforms into the product phase f. Relationship between strength and ductility i. An increased in deformation increases the tensile strength and decreases the ductility 2. Annealing (Recovery, recrystallization, and grain growth) a. As the amount of deformation increases, the dislocation density increases, thus strength increases b. Increasing the temperature will enhance diffusion and lead to the elimination of a large number of dislocations, decreasing the strength c. Annealing – the process of regaining ductility without losing tensile strength d. Recovery – some dislocations are eliminated and those remaining are rearranged into arrays that minimize the excess energy of the crystal; 150°C-250°C e. Recrystallization – the replacement of grains containing high concentrations of dislocations with new grains containing much lower dislocation densities; 250°C-350°C i. The higher the recrystallization temperature, the shorter the annealing time ii. Increasing the amount of cold work increases the driving force for recrystallization since a sample contains more stored energy at this point 3. Important Processing Methods a. Single Crystal Growth
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This note was uploaded on 09/12/2011 for the course MSE 2001 taught by Professor Tannebaum during the Spring '08 term at Georgia Institute of Technology.

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Test 4 Study Guide - Test IV Study Guide Kinetics of Phase...

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