MaterialsFinal

MaterialsFinal - Page1 0112 University of Arizona ENGR...

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Unformatted text preview: Page1 0112 University of Arizona ENGR 211R: Engineering Materials Final Exam 1. _'|l Name H '. “ ' l f’ ‘ _.0\,LL£ PART I (25 x 2 50 poianz) Qucsfions l & 2 are based on Figure l. [I] 'lhe liquidus and solidlm temperature (Figuml ) of an alloy containing 60 % Sb are (a) 630.765 °C& 271.422 °Crcspoctivcly (b) 550 °(‘& 271.422 °C respectively c 630.765 °(‘& 400 "( 'respectivcly 550 °('& 400 °C respectively [2] The amount ofcach phase (Figurcl‘) al 500 “(T for a 60 % Sh alloy is (a) Fully solid (I) l-‘ully liquid Q 50 % solid. 50 % liquid ‘ 7 ‘ "\ None ul‘lhc above L» ,0 G ‘ » : .w - I z ’ j I ’ , I 2 " g / é . —~ ._ /V / I, ‘ .3 , -V- r . 5 new -Anlrnony .\ Page2ol12 [3] Which is true about covalent bond? 3) No directionality Strong directionality (c) Forms between atoms with low electronegativity (d) Forms between atoms of different clectroncgativity values [4] What is the slip direction for BCC metals? (I) [001] b) [0n] §lll11 Him] [5] Interstitial Sites are the (a Small holes between the unit cells @‘ Small holes between the usual atoms (c) Small holes between the electrons (d) All ofthe above Questions 6 & 7 are based on following problem statement. A metal rod of length 20 cm and cross sectional area of0.0004 m2 is under tensile test. There are two loading conditions In lst loading condition the metal is pulled by a force of 20 N and the length of the rod changes to 22 cm. In the 2nd condition. the metal is pulled by a force of 27.5 N. but the change in length cannot be memed due to some problems. Assume the due to the loads are in elastic region. [6] “11181 is themodulusofelasticity ofthe metal? , _ .t . tun-v.3“ t 'L°.../ ~.. new I (a) 50000 Nz'm‘ Q— :' =31 o“ “ (b) 68.750 N/m2 1 O . 't x i @ 500.000 Nu’m‘ 17/? f . '- L C(‘U V -:: 0N“ ( _ ,L t (4- \ . fr \3 (d) 687.500 N l m2 [7| What is the change in length for 2nd loading condition? (a) 0475 (:m (b) 1.75 em # ‘ - r1 (- \ vl_l1 d) 3.75:: if f -— L 5’ NH\ .000 l E T '/ 3“ I? (“Ill fiJL/‘t 6 c- 0v 2": PageSoHZ [8| Which one is not true about sofl magnets? (11) High saturation mgnetimtion (b) Rapid response to high-li'equency magnetic fields (6) ll igh electrical resistivity ® High mmncncc [9] Which one is BCC crystal structure of iron? @ Fcrritc (b) Martensite (c) Pcarlitc (d) Austcmitc [l0| Tin behaves as a metal because (I) There is no energy gap between the conduction and valence bands b) Thcnc is large energy gap between the conduction and valence bands b 'lhere is very small energy gap between the conduction and valence hands (d) It is a metal [11[ What is the slip plane for FCC metals? (a) (001) (5) (OH) (c) (110) @(in) [12] All ol‘thc foll0wing statements regarding slip deformation are correct. except: A volume change is associated with slip. (h) Slip occurs along close-packed directions. (c) Some crystals have more slip systems than others. (d) Dislocation motion is necessary for slip. [13] The most eflicienl packing til-atoms is found in which oflhc following crystalline lattices: l. simple cubic ll‘ face centered cubic [11. body centered tetragonal IV. rhombohedral Vt hexagonal close packed (a) I only. (h) ll only. (c) lll only. @ II and V onlyl Page4oi12 [14] Find correct answer about covalent bond 9 Strong directionality ) Desire for the largest number of nearest neighbors (c) Polari7ation produces slight electrostatic charge between molecules (d) Electron transferred between atoms producing ions "5] ln cubic systems. a direction that has the indices as a plane is (a) Parallel to the plane @ Perpendicular lo the plane (e) Diagonal to the plane (d) None ol'lhe ab0ve |l6| Deformation is irreversible if (a) Hooke‘s law holds. (b) 'lhe deformation rate is slow. ® Applied stress is greater than the yield stress. (d) There is no work hardening. [l7] OlT-set yield is defined as (1) Stress at which yielding starts. b) Stress required for inhomogeneous deformation. © Stress corresponding to a specific plastic strain. ( ) Stress at the proportioml limit |l8| All ol‘the following statemmts about yield-point phenomenon are true, except: (a) Dislocation motion is responsible for yield point. b) Presence of carbon in iron is responsible for yield point in steels. 9 Upper and lower yield points are found in many aluminum alloys. ) Yield point indicates inhomogeneous deformation. [19] In regard to corrosion. which of the following is NOT true? 'lhe cathode loses mass. (b) Oxidation occurs at the anode. (c) The anode and cathode must be electrically connceted. (d) Water usually plays an important role. Page50f12 [20] During the tension deformation of a metal test bar. necking occurs when (a Plastic deformation begins: The ultimate tensile strength is reached. (e) Strain hardening canes to operate. (d) The heat ot‘dei'ormau'on causes recrystallimtion. [2|] When the temperature increases. the electrical conductivity of metal and ceramic? (a) Increases and decreases respectively (b) Increases and increases respectively c Dccreasw and deem respectively Decreases and increases respectively I22] One student was preparing for engrll lR module final exam and tried to memoriie following characteristics of Curie temperature 1. Above the Curie temperature domains do not form 2. Above the Curie temperature uniform domains form and grow 3. Above the Curie temperature the material is no longer temrmagnetic Find the most appropriate answer from the following four options regarding the relations mentioned above (a) I. ll & III are correct I. III are correct &. II is incorrect (e) I. ll & [H are incorrect (d) 1.11am correct & Ill is incorrect Questions 23 & 24 are based on figure 2 shown below. Figure 2 Page60l12 [23] The miller indices for the directions A & B are (Figure 2) (a) [001] & [0|0] respectively (b) [I I l] Jr. [l00] respectively (9 [001] & [111] respectively (a) {01013; [I l 1] respectively [24] The miller indiccs for the direction C (Figure 2) is (a) (5T2; PM A l "T (b) m2] ‘ _ ‘ (c) (212) " " , (w [5sz 4 L“ t’" —/ I I25] Find the most appropriate answer regarding Van der Waals bond (1) Strong directionality (b) Desire for the largest number of nmrest neighbors (9 l'olarimlion produces slight electrostatic charge between molecules (d) Elcclmn transferred between atoms producing ions Page'lof 12 PART II [1| Determine the Millcr indiccs oflhc plane and the dirtclion shown in figure 3? (3 p15) PageSof12 [2] Consider diffusion in MgO. The relevant constants for the diffusion coefficients of () and Mg are as follows: (a) At I300 K. calculate the ratio Dug/Do (5 pts) (b) As can be seen the activation energy for the two ions is about the same. So discarding the small difference in the activation energies, give a brief explanation as to why the ratio is so large. (4 pts) \ P (fig/R1) «a: : ; Ct (l- L flwoh ‘3 1 \fi‘b“ ’— L7> X Io— Cm M s ‘3 q L181“ C v .204"! e \ .w/OJ : I, D-) _ .ooootfia 3 (amp ‘\ I 0° Dm (3 s M 223 (0 C. Tin d‘Pmsicn (runs—haw? Co 1301, 015 Much my; Mum Ci Lin. MK . 1'81 Mam» V) IN) PageSoHZ [3| Some of the crystalline amelurcs are shown in figun: 4. Write down the name of the structures in {hr following spaces. (.3 pts) (31W,le (b) 7, 7, (Cl Figure Me) Figure 40) Figure 40:) [4] Dclcrminc the Miller indices ofthe plane and the direction shovm in figure 5. (5 PM W 1571 AK K’L\C\ V": lCC 7g: "' Mo“ FOX“ L 3 . , [OP \0 Page100f12 [5] Consider the following table for selected crystals: calculate the lattice parameter of copper from the information given in the table? (5 pts) 0.128 893 0.124 7.87 0.136 l0.22 0.143 2.7 ‘V W : 3‘0an l6] [7] Page“ of12 In a metal rod ol‘lcngth 20 cm and cm sectional area 0.02 cm2 cm: current is flowing at 2 amp. Find the voltage drop between the two ends ofthc rod. From your web-lectures you know that resistance is directly proportional to the length and inversely proportional to the cross sectional area. The proportional (2011318111 which is known as resistivity is given for this rod as 5 x IO’3 ohm ~ cm . (IO pts) r1 \, , a; (<3 mp'slohmtm .CZcm Q; 65L Fill in thcblank. (6 (s) i. Point‘A‘iscallZfi 53% Ekcncfih ii. Point‘B‘iscalled_ (K <.» I iii. Point ‘C‘ iscalled 3mm V 35m M iv. chionlis callodflEltsl/i hon, M v. Region II is called flasfipflflg, vi. Slope i.c., the ration ofAO/AE is called . l 9 C, L Realm ll Page 1201‘ 12 [8| Find the fraction of n in a 40 % B alloy at 600 "C from the following phzme diagram? (9 pls) U . § I t 2’ ...
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MaterialsFinal - Page1 0112 University of Arizona ENGR...

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