Himpunan Contoh Soalan Exam Soalan Ujian Sn Bhn

Question 1 (25 marks)

a) What is the difference between atomic structure and crystal structure?

(2 marks)

b) Niobium (Nb) has an atomic radius of 0.143 nm and a density of 8.57 g/cm3.

Determine whether it has a face centered cubic (FCC) or body centered cubic (BCC)

crystal structure. (Atomic weight : 92.91 g/mol, Avogadro’s No. : 6.022 x 1023

atoms/mol)

(5 marks)

c) Draw in a separate unit cells the following Miller indices:

(i) [ 1 2 2 ] (ii) [ 0 2 1 ] (iii) ( 3 2 1 ) (iv) ( 2 0 1 )

(8 marks)

d) Vacancy and grain boundary are the type of defects found in solid metal. Explain;

i) why they are considered as a defect.

ii) their effect on the mechanical properties of the metal

(4 marks)

e) Describe with the aid of sketches the ingot structure when metal is produced by the following

casting conditions;

i) pouring at low temperature and cast in a metal mould.

ii) pouring at relatively high temperature and cast in metal mould.

(6 marks)

Question 2 (25 Marks)

a) i) Define cold working and hot working in metal. (2 marks)

ii) When a cold-worked metal is heated to the recrystallization temperature, explain:

1. the differences in grain structure between cold worked and recrystallized metal.

(4 marks)

2. the dislocation density and residual stress between cold worked and

recrystallized metal. (3 marks)

3. the effect on the strength, ductility and hardness affected by this process?

(4 marks)

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b) (i) Sketch (in one graph) and briefly describe a typical stress and strain curve for metal,

ceramic and polymer. (6 marks)

(ii) A tensile stress is to be applied along axis of a cylindrical brass rod that has a diameter of

10 mm. Determine the magnitude of the load required to produce a 2.5 x 10 -3

mm change

in diameter if the deformation is entirely elastic. Assume the Poison ratio for brass is -

0.34.

(6 marks)


a) Distinguish between the following terms regarding a phase diagram.

i) Phase and components

ii) Inter-metallic compound and solid solution

iii) Solidus and solvus

(6 marks)

b) i) Base on data in Figure 1 construct a complete phase diagram of copper (Cu) – nickel (Ni)

on a graph paper provided . Label completely.

Figure 1

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SKMM 1613

ii) For 70% Cu-30% Ni alloy :

1. At what temperature. the solidification begin and complete?

2. What is the composition the first solid to form?

3. What are the composition of the phases at the temperature of 1200oC ?

4. Determine the mass proportion of the phases present at 1200oC

5. Explain with the aid of sketches the solidification process when the alloy is slowly

cooled from liquid phase to room temperature.

(19 marks)


a) Sketch a phase diagram of Fe-Fe3C for carbon steel up to 1130oC :

i) Name and write isothermal reaction found in the phase diagram

ii) Sketch the room temperature microstructure for 0.4%C steel. Also calculate

percentage of proeutectoid ferrite.

(10 marks)

b) Based on Figure 2 :

i) Name the heat treatment process for 0.4 % steel for treatment (a), (b) and (c)

ii) Describe how these heat treatment process are conducted

iii) For each treatment, give the expected microstructure and properties

(15 marks)

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SKMM 1613

Figure 2


a) i) Outline the significance of surface treatment processes.

ii) Suggest and explain a suitable surface treatment process for aerospace application

structure which is made of nitride steel. (7 marks)

b) What are the main alloying elements in maraging steel?. Describe how to produce this alloy

steel. (4 marks)

c) i) Give two examples of non ferrous metals and list their properties and applications

(4 marks)

ii) Suggest and explain two methods to strengthen these non ferrous metals

. (4 marks)

d) Suggest with reason a suitable non-metallic engineering materials for the following applications:

i) High performance bicycle frame

ii) Cutting tools

iii) Frying pan holder

(6 marks)

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(a) For each of the following compound, state with reason whether the bonding is metallic,

covalent or ionic. (Given : Atomic number for N=7, H=1, Al=13, C = 6 )

(i) NH3 (ii) Al (iii) C2 H6 (9 marks)

(b) Show that the atomic packing factor (APF) for Face Centered Cubic (FCC) is 0.74

(6 marks)

Question 2 ( 13 marks)

(a) Rhodium has an FCC crystal structure, an atomic radius of 0.1345 nm and an atomic

weight of 109.9 g/mol. Calculate the density of rhodium.. (Given: Avogadro’s Number is

6.023 x 1023 atoms/mole). (5 marks)

(b) Draw in a separate cubic unit cell the following directions and planes;

(i) [ 3 2 1 ] (ii) ( 1 3 3 )

(iii) ( 1 3 3 ) (iv) ( 1 2 3 ) (8 marks)


(a) With the aid of sketches give three crystal defects in metal. (3 marks)

(b) Explain with the of sketches the solidification of pure metal with the addition of grain refiner agent. ( 5 marks)

(c) (i) Describe the substitutional and interstitial diffusion mechanisms.

(ii) Which diffusion mechanism is more rapid and why? (5 marks)


(a) Name and explain two strengthening mechanisms. The explanation should include how dislocations are impeded for each of the strengthening techniques. (5 marks)

(b) Two castings of the same material were produced by using preheated sand mould and metal mould respectively. Explain with reasons which casting is stronger and harder.. (4 marks)

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Question 1 (10 marks) a) Explain the differences between covalent bonding and metallic bonding in engineering materials. (2 marks) b) For each of the following compound, state with reason whether the bonding is covalent or ionic. (Atomic number, Z : H = 1, Mg = 12, O = 8, C = 6) i) MgO ii) C2H6 (4 marks)

c) Molybdenum (Mo) has a BCC crystal structure with a density of 10.28 g/cm3 and atomic mass of 95.94 g/mol. Determine the atomic radius of this metal. (Avogadro’s No.=6.023 x 1023 atoms/mol) (4 marks) Question 2 (16 marks) a) Draw in a separate unit cells the following direction and planes;

i) (3 0 2) ii. [ 1 2 1] ii) ( 0 0 1 ) (6 marks)

b) Determine the Miller indices for the directions P, Q and planes R , S in the following unit cells;

(6 marks)

c) Compare the diffusion mechanism between interstitial and vacancy atom. Which type of the

diffusion mechanism is more rapid? Give two reasons.

(4 marks)


a) With the aid of sketches explain three types of point defects

(6 marks)

b) With the aid of sketches differentiate between an edge dislocation and screw dislocation.

(6 marks)


(a) Name and explain two strengthening mechanisms. The explanation should include how

dislocations are impeded for each of the strengthening techniques.

(4 marks)

(b) Two castings of the same material were produced by using preheated sand mould and metal

mould respectively. Explain with reasons which casting is stronger and harder.

(4 marks)

(c) Calculate the percentage of cold work for the cold worked copper rod shown in Figure 1. If the

expected percentage of cold work is 40%, what is the final diameter of the rod?

(4 marks)

(DO : initial diameter and Dd : final diameter)

Figure 1

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a) i. List three strengthening mechanisms for metal.

ii. Choose one of these strengthening mechanism and describe with the aid of

sketches.

(8 marks)

b) i. What is mean by cold working and hot working?

ii. discuss the differences between cold working and hot working in terms of

microstructure, mechanical properties and surface finish.

(8 marks)


(a) Distinguish between the following terms:

i. Cooling curve and cooling rate

ii. Pouring temperature and solidification range temperature

(4 marks)

(b) Consider the binary eutectic copper-silver phase diagram in Figure 1.

For 70%Cu-30%Ag :

i. At what temperature the solidification begins.

ii. Calculate percentage of phases present at the temperature of 850oC.

iii. Explain with the aid of sketches the solidification process form liquid state to room

temperature.

iv. Sketch room temperature microstructure

. (12 marks)

Figure 1


(a) Name and briefly explain FOUR different phases of carbon steel. (4 marks)

(b) Describe the expected mechanical properties, microstructure, and heat treatment method for

the following heat treatment processes.

i. Normalising

ii. Sub-critical annealing process

(14 marks)

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(c) Consider the magnesium (Mg) - lead (Pb) phase diagram in Figure 1. For 50%Mg-50%Pb alloy :

v. At what temperature the solidification begins and completes? (2 marks)

vi. Calculate the percentage of phases present at the temperature of 500oC. (3 marks)

vii. Explain with the aid of sketches the solidification process. ( 4 marks)

viii. Sketch the cooling curve for the alloy and the room temperature microstructure.

( 3 marks)


(c) For the terms hardness and hardenability :

i. Define these terms (2 marks)

ii. Briefly describe their standard testing method (6 marks)

(d) With the aid of sketches explain the hardenability curves for 0.5% carbon steel and 4340 alloy

steel (1.85Ni-0.80Cu-0.25Mo) (4 marks)

(e) Based on cooling paths in TTT Diagram as in Figure 2 :

i. Determine the final microstructure for all cooling paths (A to E).

(5 marks)

Figure 1

ii. Describe how treatment with cooling path B, is conducted. (3 marks)

iii. Suggest the name of treatment and example of application of the treatments

with the cooling path of D and E. (4 marks)


(a) Give two reasons why cast iron is still wide used in engineering applications. (2 marks)

(b) Briefly describe two factors that affecting the formation of carbon in cast iron either in the form

of graphite or cementite. (4 marks)

Figure 2

(c) Based on the micrograph in Figure 3 :

(i) Determine the type of cast iron (2 marks)

(ii) Describe how these cast iron are produced (4 marks)

(iii) Suggest two example engineering applications for each cast iron.

(2 marks)

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(f) Figure 1 shows a part of Fe-C phase diagram for steel. With the aid of a suitable sketches :

(i) Explain phase transformation for 0.3% carbon steel from 1000oC to room temperature.

(ii) Explain phase transformation for 1.2% carbon steel from 1000oC to room temperature.

(iii) Calculate the percentage of pro-eutectoid ferrite in 0.3% carbon at room temperature

(10 marks)

Cast Iron A Cast Iron B

(g) For the following heat treatment processes, describe the treatment process, their expected

microstructure and mechanical properties.

(i) Normalising process for 0.5% carbon steel

(ii) Quenching and tempering for 0.9% carbon steel

(10 marks)

(h) What is a suitable heat treatment to be used to strengthen small carbon steel components such

as screws, wire and nails. Describe the treatment method. (5 marks)


(a) Briefly describe two factors that affecting the formation of carbon in cast iron either in the form

of graphite or cementite.

(5 marks)

(b) Based on microstructure of cast iron in Figure 2:

Figure 1

(i) Give name and mechanical properties of cast iron X, Y and Z.

(ii) Briefly explain how these cast iron are produced

Figure 2 (9 marks)


(a) List four effect of the addition of alloying elements on carbon steel. Explain two of these effects.

(4 marks)

(b) Give four types of alloy steels and examples of applications. What is a suitable alloy steel to be

used as surgical instruments. List the main alloying elements.

(7 marks)

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QUESTION 1 (10 marks)

(a) Briefly describe the following types of primary bonding;

(i) ionic (ii) covalent and (iii) metallic.

(6 marks)

(b) For each of the following element/compounds, state whether the bonding is metallic, covalent or

ionic;

(i) Nickel (Ni) (ii) Graphite (C=C)

(iii) Copper (Cu) (iv) Magnesium oxide (MgO)

(4 marks)


(a) Determine the Miller indices for planes drawn in the following cubic unit cells

(3 marks)

(i) (ii)

(b) Draw the following direction vectors and planes in separate cubic unit cells.

x

y

z

x

y

z

½

⅓

(i) [ 1 0 1] (ii) [ 2 2 1] (iii) (0 1 1 ) (iv) (3 2 1)

(8 marks)


(a) Describe and illustrate the solidification process of metal with impurities.

(5 marks)

(b) Explain with the aid of relevant sketches the substitutional and interstitial diffusion mechanisms

in solid metals.

(4 marks)

(c) Explain the difference between point defects and linear defect.

(2 marks)

QUESTION 4 ( 18 marks)

(a) Explain what is meant by slip system and whether all metals have the same slip system.

(4 marks)

(b) Explain briefly why metals such as magnesium (Mg) and zinc (Zn) which have hexagonal close packed (HCP) crystal structures are more brittle than metals such as aluminium (Al) and copper (Cu) which have face-centred cubic (FCC) crystal structures.

(4 marks)

(c ) (i) Briefly, describe the relationship between dislocations and strengthening of

engineering metals

(ii) List the FOUR main strengthening mechanisms and provide a comparison between

them in terms of the type of barrier that will result in increased strength

(10 marks)

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(a) What is the relationship between the length of the side a (also known as the lattice constant) of

the body-centred cubic (BCC) unit cell and the radius, r, of its atoms? Tantalum at 20oC is BCC

and has a lattice constant of 0.33026 nm. Calculate its atomic radius.

(3 marks)

(b) Draw the following directions and planes in separate unit cells;

i) [ 1 1 0] ii) [2 0 3]

iii) (2 3 2) iv) (1 2 0)

(8 marks)

(c) Briefly explain with illustration dendrite formation in the solidification of a metal. Describe with

the aid of schematic drawing of ingot structures when metal is produced by casting;

i) at relatively high pouring temperature and cast in a metal mould.

ii) at low pouring temperature and cast in a metal mould.

iii) cast in a sand mould.

(8 marks)

(d) In reality metals are never perfect and contain various types of defects which affect many of

their physical and mechanical properties. Identify these defects with brief explanation and

illustrations.

(6 marks)

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SME 1613


(a) i) What are the information can be obtained from a stress strain curve?

ii) With the aid of a sketch of stress strain curves, explain the difference between a

ductile and brittle materials. Give an example of material for each.

(6 marks)

(b) A cylindrical specimen of steel having a diameter of 15.2 mm and length of 250 mm is

deformed elastically in tension with a force of 48,900 N. If modulus of elasticity and

Poisson’s ratio for the steel are 207 GPa and 0.30, determine the following:

i) The amount by which this specimen will elongate in the direction of the applied

stress.

ii) Calculate the change in diameter of the specimen. (6 marks)

(c) A piece of aluminum (Al) bar has been heavily cold worked.

i) Sketch the microstructures before and after this process. (2 marks)

ii) Describe mechanical properties after cold work. ( 3 marks)

iii) Suggest and explain a method in order to improve its ductility after cold work.

How does the ductility can be increased by this method?

(8 marks)

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SME 1613


Copper (Cu) and Silver (Ag) form an alloy with limited solid solubility system. The melting points of Cu

and Ag are 1085oC and 970oC respectively, with eutectic temperature and composition of 779oC and

71.9% Ag. At eutectic temperature, the maximum solid solubility of Ag in Cu is 8 % and Cu in Ag is 8.8%.

Assume solid solubility is 0 at room temperature.

(a) Plot and label the phase diagram of Cu-Ag on a graph paper provided. (8 marks)

(b) Consider an alloy of composition 55 wt% Cu – 45 wt% Ag is slowly cooled to room

temperature from 1100oC. Determine:

i) At what temperature the solidification starts and complete.

ii) The composition of the first solid to solidify

iii). The composition of the last liquid to solidify

(4 marks)

iv) Calculate the relative amount of pro eutectic α and eutectic β phase just below

the eutectic temperature ( TE-∆T). (4 marks)

v) Discuss with the aid of sketches, solidification process of this alloy in equilibrium

from 1100oC to room temperature. Sketch the cooling curve and room

temperature microstructure of the alloy. (9 marks)


(i) Name and briefly explain FOUR different phases (microstructures) of carbon steel.

(4 marks)

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SME 1613

(b) Briefly explain the heat treatment procedure by drawing the cooling path on the TTT diagram

provided (Figure 1) to obtain the following microstructure.

i) 100 % martensite

ii) 50% bainite and 50 % martensite

iii) 50% fine pearlite and 50% martensite. (9 marks)

(c) I) What are the advantages of martempering compared to conventional

quenching and tempering. (4 marks)

ii) How can these processes be carried out ? (4 marks)

(d) For the following carbon steel, name and explain a suitable surface hardening process.

i) 0.45% Carbon steel

ii) 0.1 – 0.2% carbon steel (4

marks)


(a) Give a suitable example of the application each made of polymer, ceramic and composite

materials. Explain why.

(6 marks)

(j) i) What is non-ferrous metals?. Give three their advantages compared to ferrous

metals.

ii) Explain how the strength and hardness of non heat treatable and heat- treatable

aluminium alloys can be increased?

(7 marks)

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SME 1613

(c ) Figure 2 shows microstructure of three different cast irons. Identify the type of cast iron,

properties and example of application and describe how each type is produced.

(12 marks)

(X) (Y) (Z)

Figure 2

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(a) Explain with the aid of relevant sketches the difference between atomic bonding in copper (Cu) and

atomic bonding in magnesium oxide (MgO).

(4 marks)

(b) Calculate the atomic packing factor for the body centred cubic (BCC) unit cell, assuming the atoms

are hard spheres.

(4 marks)

(c) The lattice constant for BCC vanadium at 20OC is 0.3039nm and its atomic mass is 50.94 g/mol.

Calculate the density of vanadium.

(Given: Avogardo’s Number is 6.02 x 1023 atoms/mol) (3 marks)


(a) Determine the Miller indices for planes drawn in the following cubic unit cells

(3 marks)

z

z

(i) (ii)

(b) Draw the following direction vectors and planes in separate cubic unit cells.

(i) [ 1 1 0] (ii) [ 3 2 1] (iii) (1 1 0 ) (iv) (2 2 1)

(8 marks)


(c) Explain with the aid of relevant illustrations point defects often found in metals. (6 marks)

(b) What factors affect the diffusion rate in solid metal crystals? Name the two main

mechanisms of diffusion of atoms in solid metals.

x

y

x

y

⅓

⅔

(4 marks)


(a) Explain how grain boundaries impede dislocation motion and why a metal having

finer grains is stronger than one with coarser grains.

(5 marks)

(d) Two previously undeformed cylindrical specimens A and B of an alloy are to be strained hardened by reducing their cross-sectional areas. For specimen A, the initial and deformed radii are 17 mm and 12 mm respectively. Specimen B, with an initial radius of 13 mm, must have the same deformation ratio as specimen A. Compute the radius of specimen B after deformation.

(4 marks)


(a) Cite the primary differences between elastic and plastic deformation behaviours.

(2 marks)

(b) For the tensile stress-strain behaviour for the cylindrical brass specimen with initial

diameter of 12.8mm and 250 mm in length is shown in Figure 1. Determine the

following:

i. The modulus of elasticity ii. The tensile strength

iii. The maximum load that can be sustained by the specimen iv. The change in length of the specimen that is subjected to a tensile stress of 345

MPa. (7 marks)

Figure 1. The stress-strain behavior for the brass specimen.



(a) Differentiate between metallic and covalent bonding and give examples.

(4 marks)

(b) Molybdenum (Mo) has a BCC crystal structure with a density of 10.28 g/cm3 and atomic mass of

95.94 g/mol. Determine the atomic radius of this metal.

(Avogadro’s No. = 6.023 x 1023

atoms/mol)

(6 marks)

(c) Draw in a separate unit cells the following Miller indices:

(i) [ 1 0 3 ] (ii) [ 1 2 2 ] (iii) ( 2 1 2 ) (iv) ( 2 0 1 )

(6 marks)

(d) (i) What is meant by diffusion in solid metal?

(ii) Describe the substitutional and interstitial diffusion mechanisms.

(iii) Which diffusion mechanism is more rapid and why?

(iv) Give two examples of engineering processes where diffusion plays an important role.

(9 marks)


(a) Distinguish between the following terms :

(i) Cooling curve and cooling rate

(ii) Pouring temperature and solidification range temperature

(4 marks)

(b) A Part of Copper (Cu)– Tin(Sn) phase diagram is shown in Figure 1.

(i) Identify phases (a) to (f) (3 marks)

(ii) Name and write two isothermal reactions (4 marks)

(iii) For alloy 90% Cu –10% Sn calculate the relative amount of phases at 900oC .

(3 marks)

(iv) Discuss with the aid of sketches, solidification of this alloy (90%Cu-10%Sn) in

equilibrium condition from 1200oC to 400

oC. (5 marks)

(v) Discuss with the aid of sketches, phase transformation for 70%Cu-30%Sn from

700oC to 400

oC. (6 marks)


A plain carbon steel containing approximately 0.6% carbon was heat treated as follows:

Heated to 900oC and quenched in cold water.

Heated to 900oC and slowly cooled in the furnace.

Figure 1

Heated to 900oC, quenched in water and reheated at 250

oC followed by air-cooled.

Heated to 900oC, quenched in water and reheated at 600

oC followed by air-cooled.

(a) Name the heat treatment process and describe with the aid of sketches the microstructure obtained

by these treatments and predict the mechanical properties.

(12 marks)

(b) Which heat treatment would you consider best with reaqsons for the following applications :

(i) 0.9% carbon to be used as cutting tools.

(ii) 0.02 % carbon steel sheet for a car body

(4 marks)

(c) Small, thin pieces of 0.5mm thick hot-rolled strip of 1080 steel are heated for 1 hour at

900oC and then given the heat treatments shown in Figure 2 ( TTT Diagram) with the

respective cooling paths.

(i) Name the microstructure of the samples after each heat treatment.

(2 marks)

(ii) Name the treatment and suggest an example of application for treatment (R) and (S).

(3 marks)

ii. Explain how heat treatment ( Q ) is conducted. (4 marks)

Figure 2


(a) (i) Differentiate between the mechanical properties of ferrous and non-ferrous alloys.

(2 marks)

(ii) List two non-ferrous alloys that are suitable for the following applications:

(1) turbine blades for aircraft engine.

(2) heating element in water heater.

(3 marks)

(iii) With the aid of a suitable sketches explain a suitable heat treatment process to

improve the mechanical properties of Al-4.5%Cu (Figure 3) for aircraft applications.

(5 marks)

Figure 3

(b) Explain the differences between polymer and ceramic in terms of:

(i) hardness

(ii) ductility

(iii) melting temperature . (3 marks)

(c) List three properties of thermoplastic and thermosetting polymers and suggest two

applications for each. (4 marks)

(d) Suggest the most suitable non-metallic engineering materials for the following components

and explain why.

(i) High performance bicycle frame

(ii) Cutting tools

(iii) Frying pan holder

(iv) Tennis racket (8 marks)

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Part of Copper (Cu)– Tin(Sn) phase diagram is shown in Figure 2.

(vi) Identify phase (a) to (e) (2.5 marks)

(vii) Name and write three isothermal reactions (6 marks)

(viii) For alloy 90wt% Cu – 10wt% Sn i. Calculate the relative amount of phases at 900oC (3 marks)

i. Discuss with the aid of sketches, solidification of this alloy in equilibrium condition.from 1200 C (5.5 marks)

ii. Draw and label completely the cooling curve (3 marks)

Exam question


A plain carbon steel containing approximately 0.6% C is heat treated as follows :

i. heated to 900C and quenched in cold water ii. heated to 900C and slowly cooled in the furnace iii. heated to 900C, quenched in water and reheated at 250C iv. heated to 900C, quenched in water and reheated at 600C.

(d) Describe with the aid of sketches the microstructure obtained by these treatments (4 marks)

(e) Mechanical properties expected (4 marks)

(f) Which treatment would you consider best for (1) cutting tools (2) dynamically stress engineering components (3) 0.02 % C steel sheet for making car body pressings

(3 marks)

(g) Small, thin piece of 0.5mm thick hot-rolled strip of 1080 steel are heated for 1 hour at 900C and then given the heat treatments shown in Figure 1 ( TTT Diagram) with the respective cooling path.

i. Determine the microstructure of the samples after each heat treatment

(4 marks)

iii. Name the treatment and suggest example of application for treatment (C) and (D) (5 marks)

iv. Explain how heat treatment ( B ) is conducted. (5 marks)

Test 2


(a) Sketch and label Fe-C phase diagram for steel up to 1130 C.. List 4 microstructure of carbon steel. (6 marks)

(b). 0.4% C steel is heated at 950 C.

i. With the aid of sketches explain phase transformation when it is slowly cooled from to room temperature. (3 marks)

ii. Calculate the weight percent austenite and proeutectoid ferrite at a temperature slightly above 723 C. (4 marks)

(c). For the following heat treatment, give a suitable heating temperature, heat treatment

method and microstructure & properties expected.

i. Spheroidizing for 0.9 % C steel ii. Full annealing for 0.2%C steel iii. Quenching and followed by tempering for 0.6 %C steel

(12 marks)

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(a) i. Briefly explain two factors effecting the formation of carbon either as graphite or cementite in cast iron. (4 marks)

ii. For white cast iron briefly explain on microstructure and properties and a method to

improve its ductility. (4 marks)

(b) Sketch the microstructure and describe how each type of the following cast iron is produced :

i. ductile cast iron

ii. gray cast iron

iii. malleable cast iron ( 9 marks)


(a) i Describe three effects of alloying elements on carbon steel (6 marks)

ii. What is the difference between tools steel and high speed steel? (4

marks)

(b) List three type of stainless steel and explain how each type of these stainless steel is strengthened. Justify your answer. (6 marks)


(a) Distinguish between thermoplastic and thermosetting. Give two examples of product for each type of plastic. (5 marks)

(b) Briefly explain processing sequences to produce a ceramic tiles. (6 marks)

(c) List three types of composite. Give two examples of matrix materials, reinforcement materials and product for each type of the composites. (6 marks)

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a) Explain the differences between covalent bonding and Ionic bonding in engineering materials. Give two example of material for each type of bonding (6 marks)

b) Molybdenum (Mo) has a BCC crystal structure with a density of 10.28 g/cm3 and atomic mass of 95.94 g/mol. Determine the atomic radius (R) of this metal.

(Given : a = 4/ R 3, Avogadro’s No.=6.023 x 1023 atoms/mol) (6 marks)

c) Determine the Miller indices for the directions P, Q and planes R , S in the following unit cells;

( 8 marks)


a) Draw and briefly explain cooling curve and solidification process for the following metals

i. Pure metal with the addition of 2wt% refining agent

ii. A binary alloy (alloy which contain of 2 type of metal)

(6 marks)

b) Sketch and briefly describe two types of crystal defect which are form during the

solidification process.

(5 marks)


a) Explain how the ductility of steel can be improved after the cold working process. Sketch

the microstructures and explain each stage of the treatment process.

(7 marks) b) Two previously undeformed cylindrical specimens A and B of an alloy are to be strained

hardened by reducing their cross-sectional areas. For specimen A, the initial and

deformed radii are 20 mm and 14 mm respectively. Specimen B, with an initial radius of

15 mm, must have the same deformation ratio as specimen A. Compute the radius of

specimen B after deformation.

(4 marks) Question 4 (10 marks)

a) Differentiate between:

i. Tensile strength and yield strength

ii. Elastic deformation and plastic deformation

(4 marks) b) Describe how a standard tensile test is conducted on a plain carbon steel

3 marks) c) From stress strain curves for three different materials in Figure 1, choose which material

has following property and why?

i. highest elastic modulus

ii. highest ductility

iii. highest toughness

Figure 1 (3 mark)

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(a) Based on phase diagram A-B (Figure 1), determine :

i. Phases of (a) to (d)

ii. Melting temperature for metal A and Metal B (6 marks)

(b) For 50%A-50%B alloy (Alloy 1), Determine :

i. Solidification start temperature and solidification complete temperature.

ii. Composition of phases at 450oC and percentage of phases at 450oC.

iii. With the aid of sketches explain the solidification process for alloy 1.

Figure 2 Figure 2

Figure 1 (14 marks)


(a) i. Draw and label the phase diagram for steel from 0 – 1130oC.

ii. Describe the change in microstructure for 0.4%Carbon steel when it is slowly cooled

from the austenitic region to room temperature.

iii. Sketch room temperature microstructure of 0.4% C steel and calculate percentage of

pro-eutectoid ferrite.

(14 marks)

(b) For the following heat treatment for 0.6% carbon steel , explain in terms of heat treatment

procedure, microstructure and properties expected.

i. full annealing

ii. quenching followed by tempering (8 marks)

(c) Explain the advantages of these heat treatment processes and describe how can these

processes can be carried-out ?

i. martempering

ii. austempering (8 marks)



(a) Distinguish between ionic and covalent bonding in engineering materials. Give example of

materials for each type of bonding.

(4 marks)

(b) At room temperature, tungsten (W) has body-centered cubic (BCC) crystal structure.

i) Sketch the crystal structure for W. Calculate the lattice parameter, a, of the unit cell if the

atomic radius, r is 0.139 nm.

(4 marks)

ii) Determine the theoretical density of W. (Atomic weight: 183.84 g/mol, Avogadro’s

number: 6.022 x 1023

atoms/mol)

(2 marks)

(c) Determine the Miller indices for the directions V, W and planes S, T in Figure 1.

Figure 1 (8 marks)

(d) The diffusion rates for carbon in titanium were determined in the Table 1.

Table 1

Temperature (°C) 736 782 835

Diffusion coefficient, D ( m2/s) 2 x 10

-13 5 x 10

-13 x

i) Evaluate the pre-exponential constant (D0) and the activation energy for diffusion, (Q,

J/mol)

ii) Calculate the rate of diffusion, x at 835 °C

Given that the diffusion coefficient, D = D0 exp ( - ),

R = gas constant [8.314 J/mol-K]

(7 marks)


(a) Distinguish between the following terms regarding a phase diagram.

iv) Phase and component

v) Solidus and solvus

vi) Melting temperature and solidification range temperature

(9 marks)

Figure 2

(b) A Part of copper (Cu) – zinc (Zn) phase diagram is shown in Figure 2.

(ix) Identify phases (a) to (f)

(3 marks)

(x) Name and write two isothermal reactions

(4 marks)

(c) For 75%Zn –25% Cu alloy :

i) Explain with the aid of sketches the phase transformation when the alloy is slowly cooled

from 600 oC to 500

oC.

(6 marks)

ii) Calculate weight percentage of all phases.

(3 marks)

γ

ε + L

δ+ L

78.5% Zn

Zn Cu


(a) Sketch and label microstructure of;

i) Hypoeutectoid steel

ii) Eutectoid steel

(6 marks)

(b) A steel rod containing 1.5 wt% carbon is heated to 1000 oC for 90 minutes and slowly cooled to

room temperature. At temperature 700 oC:

i) Calculate the percentage of ferrite and cementite phases formed.

ii) Determine the percentage of pearlite and proeutectoid cementite formed.

Use the phase diagram of Fe-Fe3C phase diagram in Figure 3 as a reference.

Figure 3

(7 marks)

(c) Figure 4 shows heat treatment process applied 0.6% carbon steel. Name and identify the

treatment, microstructure, and properties in treatment (i) and (ii).

(6 marks)

Figure 4

(d) Figure 5 shows a complete isothermal transformation diagram for an iron–carbon steel of

eutectoid composition. There are FOUR specimens, each undergo process (i) to (iv). All of the

specimen begins at 750 oC and have been held at this temperature long enough to achieve a

complete and homogeneous austenitic structure.

i. Determine the microstructure and its percentage at the end of process (i) to (iv)

ii. Explain in detail the cooling process that produce curve (ii)

iii. Suggest ONE application for each steel produced by process (iii) and (iv)

(9 marks)

Figure 5


(a) Cold work is one of the strengthening mechanisms for a metal.

i) Briefly explain how cold word process can improve the strength of a materials

ii) Describe the changes in microstructure, strength, and ductility when a cold

worked metal is subjected to annealing process.

[7 marks]

(b) Explain briefly;

i) how malleable cast iron being produced and state its special properties and

application.

ii) the different between malleable cast iron and nodular cast iron.

[8 marks]

(c) Explain why a stainless steel is corrosion resistant.

[3 marks]

(d) Name THREE types of stainless steel, cite its composition and main properties. Which of

the stainless steel can be heat treated and why?

[7 marks]

Xxxxxxxxxxxxxxxxxxxxxxxxx


(d) Consider the Lead (Pb) – Stanum (Sn) phase diagram in Figure 1. For 50% Pb-50%Sn alloy :

ix. At what temperature the solidification begins and completes?

x. Calculate the percentage of phases present at the temperature of 200oC.

xi. Explain with the aid of sketches the solidification process.

xii. Sketch the cooling curve for the alloy and the room temperature microstructure.

( 18 marks)

Figure 1


(b) Briefly describe four microstructure of carbon steel

(4 marks)

(b). Based on Fe-Fe3C phase diagram for steel, explain the phase transformation when 0.4%C steel is

heated at 950oC and slowly cooled to room temperature.

(5 marks)

(c). For the following heat treatments, describe the heat treatment method and name the

microstructures and properties expected.

iv. Spheroidizing for 0.9 % C steel

v. Full annealing for 0.2%C steel

vi. Quenching and followed by tempering for 0.6 %C steel

(12 marks)


(a). Sketch and label a typical Time-Temperature Transformation Diagram (TTT Diagram) for

eutectoid steel. Show the cooling path and explain a procedure to obtain the following

microstructure:

i). 100 % fine pearlite

ii) 100% lower bainite

iii) 50% fine pearlite + 50% martensite

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