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PDF711S - Phase Diagrams and Forming process 314 - 2nd OPP - JUN 2023 |
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nAmlBIA UnlVERSITY
OF SCIEnCE Ano TECHnOLOGY
FACULTOYFENGINEERIANNGDTHEBUILETNVIRONMENT
DEPARTMEONFTCIVILM, ININGANDPROCESESNGINEERING
QUALIFICATIOBNA:CHELOORFENGINEERIINNGMETALLURGY
QUALIFICATICOONDEO: SBMET LEVEL7:
COURSCEODEP: DF711S
COURSNEAMEP:HASDEIAGRAMASNDFORMING
PROCESS3E1S4
SESSIOJNU: NE2023
DURATION3:HOURS
PAPERT:HEORY
MARKS:65
SECONODPPORTUNQITUYESTIOPNAPER
EXAMINER(S)
Mrs).aquilineTatendKa urasha
MODERATOR:
ProfessoSrofyaMitropolskaya
INSTRUCTIONS
1. Answerallquestions.
2. Readallthe questionscarefullybeforeanswering.
3. Marksfor eachquestionare indicatedat the endof eachquestion.
4. Pleaseensurethat your writingislegible,neatand presentable.
PERMISSMIBALTEERIALS
I. Examinationpaper.
2. Non-programmablecalculator.
THISQUESTIOPNAPECRONSISTOSF4 PAGE(SIncludingthisfront page)
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Question1(20 Marks)
(a) Sketchthe planesidentifiedby the followingmillerindices.
(i) (101)
[2]
(ii) (112)
[2]
(iii) (123)
[2]
(b) Distinguishbetweenthe following:
(i) a normal grain boundary and a twin boundary.
[2]
(ii) dislocationclimband dislocationannihilation.
[2]
(c) Explainthe effectof the followingdefectson the strength of a metal:
(i) Highanglegrain boundary.
[1]
(ii)lowanglegrain boundary.
[1]
(ii)Substitutionaldefect.
[1]
(d) Theactivationenthalpy for the formationof vacanciesin copper is83 700 J/ mol,whilethe
activationenthalpy for the formationof self-interstitialatoms in copper is385 000 J/ mol.
(i) Calculatethe equilibriumconcentrationof vacanciesin copper at 1000 K.
[3]
(-ii)Calculatethe equilibriumconcentrationof interstitialatomsin copperat 1000 K. [3]
(iii)Commentand explainyour answersin (i) and (ii).
[1]
Question2 (20 marks)
Thediagrambelowshowsthe lead-tinphasediagram.
(a) Commenton the solubilityof leadand tin withineachother, and identifythe terminalsolid
solution(s)and the intermediatephase(s).
[3]
(b) PointEindicatesan invariantpoint.
(i) Identifythe invariantpoint.
[1]
(ii)Calculatethe phasefractionsin the alloyat point E.
[4]
(iii) Sketchthe microstructureof the alloy formedat point E.
[2]
(iv)Whatisthe alloy formed point Ecommonlyusedfor, and why?
[1]
(c) Considera Pb-20Snalloy.
(i)Sketchthe coolingcurve for the alloygiventhat the pouring temperature during castingis
300°(.
[3]
(ii) Calculatethe phasefractionsin the alloyat lOOoC.
[4]
(iii) Sketchthe microstructureof the alloy.
[2]
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Composition (at% Sn)
.-t 327'C
300
600
Liquid
183'C
p • 1, · G
;;:
400 ";;
5
97.8 -
8.
E
300 ,=!
100
,r +P
200
C'
00
20
(Pb)
40
60
Composition (wt% Sn)
H
- 100
80
100
(Sn)
Question3 (15Marks)
(a) Springbackincreasesasyieldstrengthincreases.Explain.
[2]
(b) A square hole 60mm on each side, or a circular hole 60mm in diameter, is to be
punched into a 5mm thick annealed titanium-alloy Ti-6Al-4V sheet at room
temperature. The UTSof the alloy is 1000 MPa.Evaluate which option is more
economic,givingreasonsfor your choice.
[3]
(c) Nameand brieflydescribethe three maintypesof extrusionoperations.
[3]
(d) A billet75 mmlongand 35 mmin diameterisextrudedat 600°( to a diameterof 20mm with
an extrusionconstantof 175MPaC. alculate
(i) the extrusionratio.
[2]
(ii) Theextrusionforce.
[3]
(iii) Explainhowyou can ensurethat all the materialisextruded,i.e.,minimaloff-cut.[21
Question4 (10Marks)
(a) Explainwhatismeantby the term weldabilityof a material?
[2]
(b) Mostcomponentsusedfor variousapplicationsare madeof partsjoinedtogether.Givefour
reasonsthat support the rationaleof joiningparts insteadof makingone completepart. [2]
(c) Suggesta joiningmethodgenerallyusedfor the followingscenarios,and givereasonsfor
your choice.
(i) Calculatorcircuitboard.
[2]
(ii) Componentthat hasto beopened regularlyfor inspectionand servicing.
[2]
(iii) Twosinkbasins,suchthat the joint ishardly noticeableand isstrong.
[2]
Endof QuestionPaper.
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