Exam 1 Solution

# Exam 1 Solution - EMA 3010 TIME 50 MINUTES MAE B 211 12.50...

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EMA 3010 TIME 50 MINUTES; MAE B 211 12.50 - 1.40 am. Wednesday Feb 11, 09 CLOSED BOOK; ANSWER ALL QUESTIONS; FORMULAS AND CONSTANTS ARE GIVEN BELOW; YOU ARE ALLOWED TO BRI NG A CALCULATOR 1: Iron has a bcc structure below 912 C and changes to a fcc structure above this temperature. The atomic radii of the iron atoms in the 1.26 and 1.29 A for bcc and fcc strctures respectively. (A) What is the number of atoms per unit cell in iron at 750 C and 950 C. [ 5 points] 75 0 () C. ) 1 cc - Ce I -,1-byy, , U C/2., 0 , V 2,) ( 0, V2-, `10 (c)What is the lattice parameter of the Iron at 750 C { 10 points} \i3 a -79 A-6 (C) What is the (100) planar density of bcc iron. { 10 points} (B) If the atoms in bcc iron are denoted as (0,0,0) and (1/2,1/2,1/2) what is location of atoms in fcc iron. [ 5 points ]

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.Fa-eize s t() Lam, (I) Name 2 planar defects than is found in BCC iron. [ 5 points] V C'" , CC) , r \ I (J) If you have a BCC form of iron and an FCC form of iron at room temperature, which structure is expected to be more ductile at room temperature and why [ 7 points] VA L.4 \ h-4.r T al Kyx j) C,fi Cel- W-) (J) [ Bonus Question 12 points ] What is the percent change in volume when BCC iron transforms to FCC iron at 912C . Show Calculations
(E) If chromium has a bcc structure similar to iron. What other characteristics it must

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