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SOL QUIZ 3 REC5%266

SOL QUIZ 3 REC5%266 - 3 80 10 7 11 2 8.314 873 6.2 10 1.013...

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plastic slower increases NAME: MSE 230-REC QUIZ #3 (30 pts) 1. Place either TRUE or FALSE in the space provided for the following statements. (3 points each) ___F____Hardness is a measure of a material’s resistance to localized e l ast ic deformation ___T____Failure by fatigue occurs after a long period of repeated stress cycling. ___F____Diffusion by the vacancy mechanism is faster than diffusion by the interstitial mechanism. ___T____Diffusivity decreases when the temperature increases. 2. A plate of α -Fe 1 cm thick is exposed to a carbon-rich atmosphere on one side and a carbon-deficient atmosphere on the other side at 600°C. The concentrations of carbon at the two faces are 0.8 kg/m 3 for and 0.4 kg/m 3 . Assuming steady state condition is achieved, what is the diffusion flux through the plate in kg/m 2 -s? (10 points) Diffusing species: C Host metal: α -Fe 7 2 0 6.2 10 / 80 / d D m s Q kJ mol K - = × = - Diffusion coefficient:
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Unformatted text preview: 3 80 10 7 11 2 8.314 873 6.2 10 1.013 10 / d Q RT D D e e m s ×----× = × = × × = × Diffusion flux: 11 10 2 3 2 1.2 0.8 1.013 10 8.1 10 / 5 10 10 C J D kg m s x----∆-= -× = -× × = ×-∆ ×-Time Steel Copper Yield Strength 3. Two dog-bone samples of i) Copper and ii) Steel are heavily coldworked at room temperature and then annealed at 300°C. As a function of annealing time, how would the yield stress vary for each sample? Indicate on the plot below. (4 points for each sample) Steel: The recrystallization temperature is 450°C, while the sample is annealed at 300°C. Recrystallization does not occur. The yield strength remains at the cold work value. Steel: The recrystallization temperature is 120°C. The sample is annealed at 300°C. Recrystallization occurs. The yield strength decreases as the the annealing time increases....
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