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Unformatted text preview: precipitation becomes thermodynamically possible. (a) If the material is cooled as indicated by the upper arrow, the final microstructure contains nuclei of ß almost exclusively in the grain boundaries of the α grains. Why might you expect this? Page 1 Engineering 45: Fall, 1990 Midterm Exam (b) If the material is cooled and then heated, as indicated by the lower path in the figure, the final microstructure consists of a dense distribution of ß precipitates in the interiors of the α grains. Why? Problem 4: Explain the following observations concerning the martensitic transformation in a particular steel: (a) The martensite transformation initiates at a given value of the temperature, M s , irrespective of the cooling rate. (b) The martensite transformation is not completed until the steel is cooled to a much lower temperature, M f , irrespective of the cooling rate. Page 2...
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This note was uploaded on 04/05/2011 for the course ENGIN 45 taught by Professor Devine during the Spring '07 term at Berkeley.
- Spring '07