Midterm02PracticeSolnsBinder

Midterm02PracticeSolnsBinder - Professor R. Gronsky...

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UNIVERSITY OF CALIFORNIA College of Engineering Department of Materials Science & Engineering Professor R. Gronsky Fall Semester, 2005 Engineering 45 Midterm 02 INSTRUCTIONS .................. LATTICE seating Please be seated with occupied seats to your front and back, vacant seats to your left and right. ...... CLOSED BOOK format All you need are writing instruments and a straightedge. Please store all books, reference mate- rials, calculators, PDAs, cell phones (OFF), and iPods. ......... NO DISRUPTION rule Questions cause too much of a disturbance to others in the room. Instead of asking questions, write any concerns or alternative interpretations in your answers. ... PROFESSIONAL protocol Engineers do not cheat on the job and they certainly don’t cheat on exams. Do not open until “START” is announced. SOLUTIONS
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1 . Defects in Solids (10 points) Mark the ballot box corresponding to the best answer. Two ( +2 ) points for correct answers, -1 if wrong, 0 if blank. ( a ) Point defects in solids include vacancies dislocations both ( b ) The defect known as a “Frenkel pair” is shown in this sketch to have body-centered symmetry an extended strain field both ( c ) Vacancies in solids participate in diffusion increase the entropy of a material both ( d ) Dislocations in solids participate in plastic deformation decrease the entropy of a material both ( e ) Fick’s First Law for diffusion flux J x = - D c x expresses the fact that diffusion requires a negative diffusivity mass flows down a concentration gradient both 2. Defects in Solids (10 points) For this problem you must draw and label all requested features directly on the figures provided. ( a ) ( 2 points ) Fill in the atoms comprising the extra-half plane and label with the conventional symbol ( ) the edge of the extra half-plane that establishes the line direction vector of the edge dislocation shown below. ( b ) ( 3 points ) On the same figure below, trace and label a Burgers circuit in finish-start-right-hand (FSRH) conven- tion, and identify the resulting Burgers vector ( b ). 1 b 1 1 2 2 2 2 3 3 3 3 F S ( c ) ( 2 points ) Fill in the atoms comprising the extra-half plane and label with the conventional symbol ( ) the edge of the extra half-plane that establishes the line direction vector of the edge dislocation shown below. ( d ) ( 3 points ) On the same figure, draw in and label the location of the slip plane on which this edge dislocation glides. Slip Plane E 45 Midterm 02 SOLUTIONS: page 2 of 6
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3 . Phases and Phase Equilibria (10 points) Refer to the Cu-Zn binary phase diagram below (from ASM Metals Handbook , 8 th edition, Vol. 8, (1973), p. 301) to answer the following questions. Recall that “brass” is the common name applied to this alloy. 10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 1100 1000 900 800 700 600 500 400 300 200 100 0 wt % Zn at % Zn Zn Cu T (°C) L !
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Midterm02PracticeSolnsBinder - Professor R. Gronsky...

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