3313 Lab 3 - ENSC 3313 COLD WORK AND RECRYSTALLIZATION...

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ENSC 3313 COLD WORK AND RECRYSTALLIZATION Lab Experiment 3 (BRING SAFETY GLASSES) INTRODUCTION When ductile metals and alloys are plastically deformed below about 0.5 of the melting temperature (T m ), they strain harden . The process is commonly called cold work . On heating to above about 0.5 T m subsequently, the material softens to its original state by recrystallizing . This involves the replacement of the distorted cold worked grains of high dislocation density (up to 10 11 cm -2 ) by equi-axial grains of lower dislocation density (~ 10 6 cm -2 ). It occurs by the growth of grain nuclei, from grain boundaries or heavy slip bands, into the deformed grains. After recrystallization is complete, the fine grain size coarsens if the material is left at temperatures above 0.5T m . Since strength decreases as grain size increases (less obstacles to dislocation motion), grain growth leads to some further softening. The fully soft state of a material is called the annealed state. A clear illustration is given in the blue
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3313 Lab 3 - ENSC 3313 COLD WORK AND RECRYSTALLIZATION...

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