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PDF711S - Phase Diagrams and Forming process 314 - 1st OPP - JUN 2023 |
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nAm I BI A u n IVE RS ITV
OF SCIEnCE Ano TECHn OLOGY
FACULTOYFENGINEERIANNGDTHEBUILETNVIRONMENT
DEPARTMEONFTCIVILM, ININGANDPROCESESNGINEERING
QUALIFICATIOBANC: HELORFENGINEERIINNGMETALLURGY
QUALIFICATICOONDE0:8BMET LEVEL7:
COURSCEODEP: DF711S
COURSNEAMEP:HASDEIAGRAMANS DFORMING
PROCESS3E14S
SESSIOJNU:NE2023
DURATION3:HOURS
PAPERTH: EORY
MARKS:65
EXAMINER(S)
FIRSOTPPORTUNQITUYESTIOPNAPER
Mrs].aquilineTatendKa urasha
MODERATOR:
ProfessoSrofyaMitropolskaya
INSTRUCTIONS
1. Answerallquestions.
2. Readallthe questionscarefullybeforeanswering.
3. Marksfor eachquestionare indicatedat the endof eachquestion.
4. Pleaseensurethat your writingislegiblen, eatand presentable.
PERMISSMIBALTEERIALS
I. Examinationpaper.
2. Non-programmablcealculator.
THISQUESTIOPNAPECRONSISTOSF4 PAGE(SIncludingthisfrontpage)
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Question1(20 Marks)
(a) Somemetalscrystallizein the FCCand HCPcrystalstructures.
(i) Giveany twosimilaritiesfoundin the FCCand HCPunit cells.
[2]
(ii) Giveany three differencesfoundin the FCCand HCPunit cells.
[3]
(iii) Although they have some similarities, FCCmetals are generally more ductile
comparedto HCPmetals.Explainwhy.
[I]
(iv) Giveone exampleof a metal that havethe FCCand HCPcrystal structure at room
temperature respectively.
[2]
(b) Distinguishbetweenthe followingterms:
(i) Vacancyand interstitialdefect.
[I]
(ii) Stackingsequenceand a stackingfault.
[I]
(ii) Dislocation,angdrain boundary.
[I]
(c) Magneticsusceptibilityisa characterizationtechniqueemployedin metalsto determinetheir
magneticbehaviour.Thediagram belowshowsthe intensity of magnetizationobservedin
iron and nickelin differentcrystallographicdirections.
(i) It isclearthat the intensityof magnetizationisdifferentin differentcrystallographic
directionsin the effectivefieldof below700 Gaussesand below400 Gaussesin iron
and nickelrespectivelyW. hatisthe commonterm usedfor thisbehaviour? [1]
(ii) Calculate the linear density for [100] and [111d]irections in iron and nickel
respectively.
[4]
(iii) Commenton the observedmagneticbehaviourin relationto lineardensity. [I]
1800
- 1600
Iron
..c·
._g 1400
N
1200
eC
Cl
1000
0 800
-~
$ 600
.f:
400
200
0 ...__....__._____.__.___..___.~..____.____.__.._~-
0
200
400
600
800
1000 Gausses
Effective field, H (Gausses)
(d) Determinethe directionindicesfor (i) lineom,(ii) lineon,and (iii) lineopin the cubicunit cell
shown below.
[3]
[001)
[100)
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Question2 (15marks)
Thediagrambelowshowsthe Cu-Niphasediagram.
(a) Commenton the solubilityof the twoelementsin eachother,and explainyour answer. [1]
(b) Whattype of solidsolutionisformedin thisalloysystem.Explainyour answer.
[2]
(c) If CuisalloyedwithZn,willa similarphasediagrambegenerated?Explainyour answer.
[2]
(d) Considera Cu-25Nialloy.
(i) Sketchthe coolingcurve for the alloy giventhat the pouring temperature during
castingis13000C.
[3]
(ii) Calculatethe phasefractions.
[4]
(iii) Ifthe alloy is cast into a sand mould where it coolsslowly,explainand sketch the
expectedmicrostructureand clearlylabelallthe zones.
[3]
Composition (at% Ni)
0
20
40
60
80
1600 ,-----r-----,-----.-------,----r---,--------r-----,
1500 -
100
- 2800
1100
1085'C
1000,__ __
0
(Cul
"""--','---"-'---'-'-....._____.
20 25
40
_ __._ ______
60
80
Composition (wt% Ni)
___,
100
(Nil
Question3 (20 Marks)
(a) Asinglepassrollingoperation reducesa 20mm thickplateto 18mm.the startingplatewidth
is 200mm, and the roll radius is 250mm, with a rotational speed of 12rpm. The contact
lengthis22.36mm,and the true averagestressis300 MPa.Calculate
(i) Thedraft.
[2]
(ii) The reduction.
[2]
(iii) Thecoefficientof friction.
[2]
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(iv) The roll force.
[3]
(v)Thepowerrequiredin thisoperation.
[2]
(b) Thepicturesbelowshowdefectiveproducts. Identifythe defect,in whichprocesseachdefect
iscommonlyexperienced,and correctiveactionto be taken.
[9]
(i)
(ii)
(iii)
Question4 (10marks)
(a) Weldabilityisoften consideredto be a materialproperty.Whatother twofactorsaffectthe
weldabilityof a material?
[21
(b) Distinguishbetweenthe two broad typesof welding,and givetwoexamplesunder eachclass.
[3]
(c) Withthe aid of a welllabelledschematicdiagram,brieflydescribethe fusionweldstructure. [5]
Endof QuestionPaper.
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