ss_5 - 27. Consider glass formation from three iiquid...

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Unformatted text preview: 27. Consider glass formation from three iiquid materials with different viscosities: (l) a very low viscosity pure metal; (2) an intermediate viscosity thermoplastic polymer; and (3) a very high viscosity silica-based glass. a) On the diagrams below, sketch TTT diagrams that describe regions for crystallization and glass formation (amorphization) for each of these three materials. C5D} u..| .4 3 3 3 Temperature ': / Temperaiure —| Temperature METAL POLYMER SILICA arrow WW“ I l\ Th “'fi_w*” w“ E ” ‘ M d m a i \ _ a “w r , mm " M- WM * “if”, 5. Suppose a thin film of pure Boron i Mm thick is sandwiched between thick wafers of Si, each 1mm thick and then annealed at T=1200°C. Sketch a series of three or more curves, including one at time t=O, describing the Boron concentration in this system as a function of time (no calculations are needed here). kmw kfi-S-USFES C W M ZWK t: 3 \ an NEAL $L\C§'z _ OM45 \J‘D We SK 0N ENOK $33595. \H 9. The diffusivity of C in BCC Fe is 2.45x10'12 mzfsec at 500 0C and 3. 16x101 1r1t1‘~",*’sec at 700 0C. Using these data, develop an Arrhenius-type expression ( D(T) = Doexp[-ka3T] ) describing the temperamre dependence of this diffusivity. Using the expression L=[Dt] 1" 2 to estimate the depth of carbon diffusion from a surface, estimate by what factor the time, t, to carburize a steel surface will be reduced by raising a carburization temperature by 100 0C. \Cg; fiVS _2 j _ 7M1 -_ —__., “gamma (3 I A) 15> Q " \H: '=— 0 CB“ 9}) OOOOZEE fl Rt #2:“; E, - “’— TA kL *& ® 11. A. Why does a diffiasion coefficient depend on temperature? B. Would you expect the diffilsion coefficient of an AI atom along an Al-AI grain boundary to be higher, lower, or the same as the diffusion coefficient of an A1 atom through the bulk of an Al grain? Briefly justify your answer. P: beVU$WN £03990?ch EEPMS 09 _ Ww>mw $.33; mo mung, Page Fall bstw %‘-{ N gmwm hugmfim} WE evenedwa CDQWWWDQ (SE; V-WCKE’Ss \ucmfipg w\\\+ mam-awe va‘wmz. $e¢cmn5 mom: Mimi/hm BMWM$2S \u WEE \mN \Wfixw W‘PWW 5 Nb w. wackmmmx WT No Max Cm mag/mm 24. Use the Hume-Rothery rules to assess the solid solubility of copper in silver. Compare your prediction with the Ag-Cu phase diagram. _ h C F E‘UWW Cififis “mus {A @0333“? um M R: O.\“\”\ \fik +\ Cu $0; 0,ng \o‘a *Zfl O___.—--—'\”M' ORE \W - \7 £7» 0.0%. NU'K'VkL Souk @kufimU‘V I n “55‘ WDP°$W “57 an L 1: 1° *9 Cowufirez boxovmuw. I WLB \8 \mm W: (MOE; 1 W. mac mods , egwssl-wa 05— Co “AGED a _ \s \m 4x7” Ms NT 0:- M \p Lab VS “M WA. 90 100 30 i0 50 60 1’0 30 £9 ‘0 20 #1031”: ?E9 CENT COPPER Cu 25. Use the data in the Table below to develop a brief argument why a large amount of nickel (Ni) can be dissolved in copper (Cu) while only a very small amount of lead (Pb) can be dissolved in copper. atom crystal electro- element radius mm] structure negativity valence Cu 0. 128 fee 1 .8 +2 Ni 0. 125 fee 1 ‘8 +2 Pb 0.175 fcc 1.6 +2, +4 W ijhhufiz9> m_ $Dmh. EDLUBU‘W ?%\)x\>§a\ By W W Vemay imm$ SoWT we? Co mm 3mm: W P me. \‘\\D\\ Sexu¥a\\,m \m EDA 0W) Nb \ \c, xemzab W1 We @WHL—xstML \5 PM eneming out menus BxSSPLN/S 32. The mechanical properties of a particular steel known as type 4340 are given in the table below for two conditions. a) For the annealed case, sketch a possible (well labeled) stress-strain diagram for these two materials. b) Briefly explain the process by which this same steel can be hardened and what effect this process has on the steel structure. c) Which of these two steels is more brittle? Why? 0? mm W WM 1725 1587 0.4;" 0.\O 03$ 0.20 0.2: (‘9 «v w chso ewe \C: WM}: “5‘” l’" thamw\ at "no N kuswsa‘hr; VW‘Q- “U33 UNOB kobm to} “oz, Meats: 3 \T car: she; ‘64:?) fika QWpcutkL “w Nil-{gswe- Mmmsxw mug-xi» mm 3323?. © spew \"st Ma 3&smutcmw WQ’EP‘U'I’ W IF??— Pr kOUJ‘EcL \D ‘R-VL Wfic lashes. ems bows \W’z ITS sat/mm M— W QXVQJSE 55" Vikki-WI: 5?, .. 33. Consider a large plate of 1080 (0.8 Wt%C) plain-carbon steel 1” thick. The plate is initiain held in an annealing furnace at a temperature of 800°C. The plate is removed from the furnace and subjected to a water spray on both sides which fixes the surface temperature at 25°C. After 100 see, the temperature at the center of the plate is 500°C. For t=100 see: A) sketch a schematic diagram of temperature as a function of plate thickness. B) sketch a schematic diagram of hardness as a function of plate thickness. C) draw a wen-labeled sketch of the microstructure at the plate surface and at its center. Suppose instead of woflcing with 1080 steel, the same conditions are applied to a plate of Fe- 0.001wt%C alloy. Repeat parts A-C. 14. Using the Cd — Zn equilibrium binary phase diagram, determine: a. the melting temperature of pure Cd. b. the melting temperature of pure Zn. c. the eutectic temperature and eutectic composition. (1. the maximum solid solubility of Zn in Cd. e. the maximum solid solubility of Cd in Zn. 15. For a composition of Zn — 30 wt% Cd and for each of the three temperatures — 400 0C, 270 oC, and 150 0C: a. determine which phase or phases are present b. determine the composition of each phase 0. determine how much of each phase is present d. sketch 3. possible microstructure. H00 2560 \30 ® \,_ *L @s .-. _g’_—o "- ® C: "saw/‘06} C ': \rguflccfl (UL :AA (61 b C 2 @rQW eat a}. 2 flows/009 M N" M L. -‘ EEK: PER cm zzxc—— IIIIIIII u ' p 5 1o 15 20 25 so as so so a as so 450 TEMPERATURE-INC to 10 29 o 50 so 70; so 90 100 ca name 95R cammc Zn 29. Refer to the C-rich portion of the Fe—Fe3C phase diagram. (a) what is the eutectoid temperature and eutectoid composition? (b) what is the maximum solid solubility of C in ferrite? (0) what is the maximum solid solubility of C in austenite? ((1) Why is the solubility of C higher in austenite than in ferrite? (e) What is the maximum solubity of C in ferrite at T-2000C? (f) Consider a Fe-O.8Wt%C alloy. For T = 1000°C and 700°C determine: what phases are present the composition of each phase how much of each phase is present a qualitative sketch of the microstructure (g) Suppose a Fe-0.8wt%C alloy is cooled slowly through the eutectoid temperature then: (i) held for a long time at 700°C; or (ii) quenched to room temperature. For each of these two cases, sketch the microstructure you would expect. Briefly justify your sketches. ® mew/ac: ® mast. '— “tn-“C, I ' '1 FEW-Va F \‘\ X \x (X O bC \S'ru. ® 7% ramswa N $¥>kcéfi mi, Wiggle \w s :2. W tee: so x9» 443 mass Mam-csz we Lew‘ WEE 2W. ...
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ss_5 - 27. Consider glass formation from three iiquid...

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