Materials Assignement 6 Attempt 1

Materials Assignement 6 Attempt 1 - WebCT Quiz Homepage

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WebCT Quiz Homepage http://webct.mcmaster.ca/SCRIPT/MATLS_1M03_T2_06_newRestore/s. .. 1 of 4 31/03/2006 5:37 PM View Results Name: BRYCE JONES Attempt: 1 / 3 Out of: 9 Started: March 30, 2006 1:03pm Finished: March 31, 2006 5:36pm Time spent: 28 hr, 33 min., 31 sec. Question 1 (1 point) Calculate the rate (in s^-1) of a reaction that obeys Avrami kinetics, knowing that the constants n and k have values of 1.5 and 4.4 x 10 -3 , respectively. Use scientific notation, significant figures in answer: 2 Student response: 3.8e-2 s^-1 Correct answer: 3.4E-2 (3.4 * 10 -2 ) s^-1 General feedback: The Avrami equation is: where y is the fraction of the transformation that has occured at time t . The rate of transformation is given by: In order to solve for r , we need to determine how long it takes for half the transformation to occur. Making y = 0.5, we get: We solve for t , substituting our values for n and k , and then use that value in the rate equation above. For more information, see the section on The Kinetics of Solid-State Reactions in the text. Score: 0.1 / 1 Question 2 (1 point) Which of the following describes recrystallization ? Student response: Correct Response Student Response Answer Choices a. Diffusion-dependent with a change in phase composition. b. Diffusionless. c. Diffusion-dependent with no change in phase composition. General feedback: Recrystallization is diffusion-dependent but does not involve a change in phase composition. For more information, see the Basic Concepts section of the chapter on Phase Transformations in Metals in the text. Score: 0 / 1 Question 3 (1 point) Consider the TTT diagram for a steel of eutectoid composition (Fig. 10.13 in the text). What phases will be present if the material is given the following heat treatment: annealed at 800 C, cooled rapidly to 350 C and held for 10 s heated rapidly to 650 C and held for 1 h
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Materials Assignement 6 Attempt 1 - WebCT Quiz Homepage

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