{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

PracticeSol3

# PracticeSol3 - \$Lu7/‘ONS ME 083 Spring 2001 Structure and...

This preview shows pages 1–7. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: \$Lu7/‘ONS ,/ ME 083 Spring 2001 Structure and Properties of Solids Practice Exam #3 April 6, 2001 Problem 1: Microstructure Thin strips of A181 1045 steel are heated into the austenite region and allowed to come to equilibrium. Sketch and label the the resulting microstructure of the samples, and calculate the weight fraction of each phase if the steel is: (a) furnace cooled to room temperature A/S/ /O 45' ”‘9' O, 45%C Or 76 _ 0'45 = om W (b) quenched rapidly to room temperature /00 % M43919? No 0488/5245“ (c) quenched rapidly to room temperature and then heated to just below the eutectoid tem- perature and held for a. long time before slow cooling to room temperature Problem 2: Microstructure On the axes below, draw a. schematic TTT diagram for a plain carbon steel containing 0.45 wt% carbon. The eutectoid temperature as well as M, and M f temperatures are shown on the graph. The nose of the curve is at 0.5 s and 580 “C. Be sure to label all transformations. 1000 § § Temperature [°C ] A 8 § 0.1 0'5- 1 10 100 1000 Time [ see] Figure 1: TTT diagram for plain carbon steel containing 0.45 wt% C. Problem 3: Phase Diagram Sterling silver is an age hardenable binary alloy with copper as the alloying element. (a) From the information below, sketch the Ag~Cu phase diagram and label all regions. — Cu melts at 1084 ”C - Ag melts at 962 l’C — Eutectic reaction at 780 “C: L(28.1 wt% Cu) goes to a (8.8 wt% Cu) and ﬁ (92 wt% Cu) — Solubility of Cu in Ag at 400 ”C: 1 wt% —-— Solubility of Ag in Cu at 400 I"C: 2 wt% O /00 % s _ , . (r (ow w 0/ // (7%E7Prr7J/7w #AQQQ/wo) w “Lg/5% (b) Suggest a Ag-Cu composition and heat treatment that might result in precipitation hard— ening due to precipitation of B. (i) Composition? < 8! 9 M% m (ii) Solution heat treatment temperature? T > SOLWS (iii) aging temperature? T4 SOLVUS ") ("00* #969047 raw EMU/u (x773 EDWAW/FQO OW o< W 60% @ramz—zo gay ﬂew?— * '2) ﬁWW Tx—ri/ ﬂ SME/QE/WF ,43 PW?” 06% Wag—g Problem 4: Kinetics When an A181 1080 steel transforms form austenite to bainite, one process which takes time is the diffusion of carbon to regions where carbides are forming. (a) This process appears to obey an Arrhenius type equation: 15 = Aexp (%) , (1) where R220 cal/mol-K. If the time required for carbide to start precipitating at 500 ”C (773 K) is one second, and 60 seconds are required at 300 "C (573 K), calculate how long _ one would have to wait for the beginning of precipitation at 250 ”C. (b) : Explain why, in general, for an isothermal phase transformation, the larger the amount of under-cooling (AT) the ﬁner the resulting microstructure. Nocmw 8A7? f“ As ATP Mac/ow ( 619wa 34%) ,4 L—"ae- smear; ewe-owe: => 9%? Mcfo Wagner (c) : Explain the difference between hardness and hardenability. ﬂ/AQO/UEES : ﬁrs/44¢, Mil/me; 920/2297 HAeoavwz/ry .v #55 MW Mir/M mayo 972— L9 5 E9751) Problem 5: Miscellaneous (:1) A normalized plain carbon steel exhibits a microstructure consisting of 60% pro—a: and 40% pearlite. With reference to the Fe—Fe3C phase diagram, estimate the carbon content of this alloy. 4079M? "%#0% 3(a7ga9t%c @3727EL set/WW" 04 52%;: %> (50,32, w%c (b) An aluminum crystal slips on the (111) plane in the [110] direction, with a 3.5 MP3. (500 psi) stress applied in the [111] direction. What is the critical resolved shear stress? / 56%1/7/05 MAJ as: Mar/Wei 2 [Hang/“1:7 Composition (aﬂ- C? 1200 25 2500 Tampemtua PC) 1500 Cermm‘lita (53¢) (Fe) Composition (W196 C) Figure 2: Fe—Fe3C phase diagram. 0.15%; 1030 6‘ 70 Temperature (“F3 ...
View Full Document

{[ snackBarMessage ]}

### Page1 / 7

PracticeSol3 - \$Lu7/‘ONS ME 083 Spring 2001 Structure and...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online