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PDF711S - Phase Diagram and Formatting Processes 314 - 2nd Opp - June 2022 |
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r
nAm I BI A un IVE RS ITV
OF SCIEnCE Ano TECHnOLOGY
FACULTYOF ENGINEERINGAND SPATIALSCIENCES
DEPARTMENT OF MINING AND PROCESSENGINEERING
QUALIFICATION: BACHELOR OF ENGINEERING IN METALLURGY
QUALIFICATION CODE: 08BMET
LEVEL: 7
COURSE CODE: PDF711S
COURSE NAME: PHASE DIAGRAMS AND FORMING
PROCESSES314
SESSION: JUNE 2022
DURATION: 2 HOURS
PAPER: THEORY
MARKS: 65
EXAMINER(S}
SECONDOPPORTUNITYQUESTIONPAPER
Mrs. Jaquiline Tatenda Kurasha
MODERATOR:
Professor Sofya Mitropolskaya
INSTRUCTIONS
1. Answer all questions.
2. Read all the questions carefully before answering.
3. Marks for each question are indicated at the end of each question.
4. Please ensure that your writing is legible, neat and presentable.
PERMISSIBLEMATERIALS
1. Examination paper.
2. Non-programmable calculator.
THIS QUESTION PAPER CONSISTS OF 4 PAGES (Including this front page)
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Question 1 (15 Marks)
{a) What is the stacking sequence of the BCCcrystal structure. Explain you answer.
[2]
(b) Consider the diagram below. Determine the miller indices of
{i) plane vwx
[2]
{ii)direction xv.
(1.5]
(iii) direction vw.
[1.5]
{c) Copper and gold both have an FCC crystal. Will they produce the same x-ray
diffraction pattern? Explain you answer.
[2]
{d) A beam of X-rays of wavelength 0.071 nm is diffracted by the {110) plane of a nickel
sample with lattice constant of 0.353 nm.
{i)
Find the angle at which second-order diffraction takes place.
[2]
(ii) Calculate the interplanar spacing.
[2]
(e) The size of Brinell indentation taken on a steel specimen was found to be 6mm.
Diameter of the ball indenter is 10mm. Estimate its hardness. The test load was
2000kg.
[2]
Question 2 {15 marks)
The diagram below shows the copper-nickel phase diagram.
(a) Comment on the solubility of the two elements in each other, and explain your
answer.
[2]
(b) What type of solid solution is formed in this alloy system. Comment on your answer.
[2]
(c) If Nickel is alloyed with silver, will a similar phase diagram be generated? Explain
your answer.
[2]
(d) Consider a Cu-25Ni alloy.
(i)
Sketch the cooling curve for the alloy given that the pouring temperature
during casting is 1300°C.
[3]
(ii) Calculate the degrees of freedom, and comment on your answer.
[2]
(iii) Calculate the phase fractions.
[4]
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0
1600
Composition (at°/~ Ni)
20
,10
50
- 1500
1400 - --
E
""'' 1300 -
0.
E"'
1200 -
LIQU!d
-
.-
80
100
2800
i,.53--c
- 2600
....
2"-00
"""'''
",,'if!.
- 2200
1100
10B~:-c
I
I
1000
I
III
0
20 25
40
60
80
(Clll
Composition (wt~i:. N1)
.:__ 2000
100
(N1)
Question 3 (15 Marks)
(a) Explain why forged components have better strength and toughness compared to
components made from other forming processes.
[2)
(b) (i) One way of classifying forging operations is by considering the force application. By this
classification, name and briefly describe the two ways deformation force is applied.
[2)
(ii) Why is a flash required in impression die forging?
[1]
(c) A hot upset forging operation is performed in an open die. The initial height and diameter of
the workpiece are 50mm and 25mm respectively. At the end of the stroke, the average
diameter of the workpiece is 50mm, and the flow stress is 85MPa. The coefficient of friction
at the die-work interface is 0.4.
(i) Calculate the height of the work piece at end of the stroke.
[2)
(ii) Calculate the forging force at the end of the stroke.
[3)
(d) (i) Name and briefly describe the three main types of extrusion operations.
[3)
(ii) Explain how to can ensure that all the material is extruded, i.e. minimal off-cut.
[2)
Question 4 (20 Marks)
(a) The strength of the welded joint depends on faying surfaces. Explain this statement, and
explain what faying surface means?
[2)
(b) Name and distinguish between the two broad types of electrodes used in arc welding. [4]
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(c) Distortion/warping is a serious problem in fusion welding. Suggest three ways to minimize
distortion.
[3]
(d) With the aid of a diagram, explain what heat affected zone (HAZ) means in fusion welding,
and describe the microstructure observed in the HAZ.
[3]
(e) Mechanical joining is generally classified as non-permanent joining.
(i)
Give one exception to this classification and suggest three circumstances under
which the exception is used.
(4]
(ii)
Give two advantages and two disadvantages of mechanical joining.
(4]
End of Question Paper.
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