Material Science
The property of a material which enables it to resist fracture due to high impact loads is known as:
- elasticity
- endurance
- strength
- toughness
The property of a material by which it can be beaten or rolled into sheets is known as:
- Malleability
- Ductility
- Plasticity
- Elasticity
The impact strength of a material is an index of its:
- Toughness
- Tensile Strength
- Capability of being cold worked
- Hardness
The materials having same elastic properties in all directions are called:
- ideal materials
- uniform materials
- isotropic materials
- real materials
The malleability is the property of a material by virtue of which the metal:
- Can be rolled or hammered into sheet
- Regains its shape and size after the removal of external forces
- Retains the deformation produced under load permanently
- Can be drawn with the application of tensile force
In compression test, the crack of the specimen of the cast iron will be at:
- The axis of load
- An oblique plane
- At right angles to the axis of specimen
- Will not be
Which of the following materials has the maximum ductility?
- Aluminium
- Nickel
- Tungsten
- Iron
Which of the following materials has nearly zero coefficient of expansion?
- Silver
- Selenium
- Invar
- Stainless Steel
The ability of a material to resist deformation or deflection under stress is known as:
- Ductility
- Mechanical strength
- Stiffness
- Toughness
The stiffness is the ability of a material to resist:
- Deformation under stress
- Externally applied forces with breakdown or yielding
- Fracture due to high impact loads
- To relieve internal stress
The ability of a material to deform without breaking is called:
- resilience
- creep
- plasticity
- elasticity
Hypoeutectoid steel consists of:
- Primary ferrite and pearlite
- Primary cementite and pearlite
- Proeutectoid cementite, pearlite and transformed ledeburite
- Pearlite
A steel with 0.8% carbon and 100% pearlite is called:
- Eutectoid steel
- Hypo-eutectoid steel
- Hyper eutectoid steel
- Pro eutectoid steel
Which of the following is/are a ferromagnetic material?
- Tungsten
- Nickel
- Copper
- Aluminium
Which of the following is an example of paramagnetic material?
- Gold
- Tantalum
- Copper
- Silver
The temperature at which the new grains are formed in the metal is called?
- Lower critical temperature
- Upper critical temperature
- Eutectic temperature
- Recrystallisation temperature
A condition of timber during seasoning in which the different layers of wood are under stress by being under compression across the grain (usually due to rapid surface drying in the kiln).
- Case hardening
- Air seasoning
- Air drying
- Strain softening
In Rockwell hardness testing method, the hardness of a material is measured by:
- Material failure
- Depth of indentation
- Elongation of material
- Surface roughness
A carbon steel having a Brinell hardness number 100 should have ultimate tensile strength closer to:
- 220 N/mm²
- 150 N/mm²
- 800 N/mm²
- 350 N/mm²
Cup and cone type fracture occurs in the case of:
- Cast iron
- Round specimen of ductile metals
- Tough steel
- Soft brass
The word ‘Brinell’ is associated with:
- soil testing
- tensile testing
- hardness testing
- testing of seasoning of wood
What is common between Rockwell, Brinell and shore? They pertain to:
- Surface finish
- Heat treatment
- Metal turning
- Hardness
Which of the following surface hardening processes needs no quenching?
- Induction hardening
- Flame hardening
- Nitriding
- Case carburising
The lower critical point for all steels is:
- 600°C
- 723°C
- 800°C
- 913°C
In which of the following process does mild steel absorb carbon and nitrogen to obtain a hard surface?
- Carburizing
- Cyaniding
- Nitriding
- Annealing
Age hardening is related to:
- silver
- duralumin
- brass
- copper
Chilled cast iron is produced:
- By adding magnesium to molten cast iron
- By quick cooling of molten cast iron
- From white cast iron by annealing process
- All of the options
Which of the following phase is obtained as the end product, after complete heat treatment cycle in austempering process?
- Pearlite
- Bainite
- Martensite
- Austenite
________ is formed when martensite is warmed to about 400°C.
- Pearlite
- Austenite
- Troosite
- Bainite
Which of the following is the hardest constituent of steel?
- Ledeburite
- Austenite
- Martensite
- Bainite
Which of the following processes permits the transformation of austenite to martensite, throughout the cross-section of a component without cracking or distortion?
- Tempering
- Annealing
- Austempering
- Martempering
Cyaniding is carried out at a temperature of ________.
- 300°C
- 500°C
- 950°C
- 175°C
The temperature point at which the change starts on heating the steel is called:
- Point of recalescence
- Point of decalescence
- Lower critical point
- Upper critical point
Which carburising method has high production rate?
- Solid powder carburising
- Liquid carburising
- Pack carburising
- Gas carburising
The diffusing hardening element in case of the carburizing process is:
- Nickel
- Manganese
- Chromium
- Carbon
How long should a steel component be heat treated before nitriding?
- 5-20 hours
- 300-500 hours
- 21-100 hours
- 100-200 hours
Which of the following is/are the objective of Normalising?
- All of the options
- To improve the machinability
- To remove internal stresses
- To enhance the mechanical properties
Which annealing process is carried out in a heavy casting to make austenitic grains homogeneous?
- Full annealing
- Process annealing
- Diffusion annealing
- Spherodise annealing
Cyaniding involves the addition of ______ for the hardening of surface.
- Nitrogen
- Niobium
- Neon
- Nichrome
Which of the following is the most common substrate material for hot-dip metallic coating?
- Aluminium
- Steel
- Zinc
- Terene
18/8 stainless steel consists of:
- 18% Nickel and 8% Chromium
- 18% Chromium and 8% Nickel
- 18% Vanadium and 8% Chromium
- 18% Nickel and 8% Vanadium
Brass is an alloy of:
- copper and zinc
- copper and tin
- copper, tin and zinc
- none of these
Silicon steel is widely used for:
- Cutting tools
- Connecting rods
- Motor crank shafts
- Transformers
Lathe bed is made up of:
- High carbon steel
- High alloy steel
- Mild steel
- Cast iron
Malleable cast iron is produced:
- From white cast iron by the annealing process
- From white cast iron by the carburizing process
- By adding magnesium to molten cast iron
- By quick cooling of molten cast iron
Gun metal contains 2 percent of:
- Tin
- Zinc
- Copper
- Nickel
What is the melting point of zinc?
- 621°F
- 787°F
- 2646°F
- 1204°F
The binding material used in cemented carbide tools is:
- Silicon
- Tungsten
- Cobalt
- Chromium
Which of the following material has maximum malleability?
- Wrought iron
- Lead
- Soft Steel
- Copper
Steel containing less than 0.15% carbon content is known as:
- High carbon steel
- Medium carbon steel
- Dead mild steel
- Stainless steel
Grey Cast Iron contains carbon % as:
- 0.3 to 0.5%
- 0.5 to 3.0%
- 3.2 to 4.2%
- 4.2 to 6.0%
Which of the following forms of iron has get the highest carbon content?
- Mild Steel
- Stainless Steel
- Wrought Iron
- Cast Iron
The metallurgical process in which a metal is obtained in a fused state is called:
- roasting
- calcinations
- froth floatation
- smelting
Which is the purest form of iron?
- Cast iron
- Wrought iron
- Mild steel
- High Carbon Steel
Which is the most efficient of the following insulating materials?
- Corkboard
- Glass fibre sheet
- Mineral fibre sheet
- Foamed urethane sheet
For making spiral staircase, ideal materials is:
- pig iron
- cast iron
- wrought iron
- steel
Metallic tapes are made of:
- Steel
- Invar
- Cloth and wires
- Nickel
Bitumen paints offer:
- pleasing surface
- hard surface
- smooth surface
- protective surface
Polymer which can be processed in both fiber or plastic material is:
- Nylon 66
- Polyethylene terephtholote
- Nylon 6
- None of the above
Stainless steel resist corrosion due to:
- Carbon
- Manganese
- Chromium
- Sulphur
The empty portion of cupola above the preheating zone is called as:
- slack
- brow
- billet
- stack
Soft iron is used in the manufacture of electromagnets because of its:
- high saturation magnetization only
- low retentively only
- low coercive field only
- high saturation magnetization, low retentively and low coercive field
Stainless steel resists corrosion due to:
- Carbon
- Sulphur
- Vanadium
- Chromium
Which alloy steel would be used for making leaf and coil springs?
- Nickel-Chrome
- Vanadium
- Silicon-Manganese
- Chrome-molybdenum
A pigment generally used to impart white colour in a paint is:
- graphite
- lead
- copper sulphate
- zinc
Slow plastic deformation of metal under a constant stress is known as:
- Creep
- Fatigue
- Endurance
- Plastic deformation
For a fully reversed loading condition in an S-N diagram, the mean stress is:
- Negative
- Equal to half of the maximum stress
- Equal to the maximum stress
- Zero
A metal which is ductile in tension can become brittle:
- in the presence of notches
- under hydrostatic compression
- in the presence of embrittlement agents such as hydrogen
- all of these
Which modern construction material is known for its strength to weight ratio and is commonly used in innovative architectural designs?
- Brick
- Plywood
- Carbon Fiber
- Reinforced
Which of the following property is the fine grained structure?
- Corrosion resistance
- Ductility
- Hardness
- Creep resistance
In the design of a shaft, the presence of keyways, holes, or other notches can introduce stress concentrations. What is the typical method to compensate for these stress concentrations?
- Increasing the shaft diameter proportionally to the notch depth
- Applying a surface treatment to the notched region
- Introducing fillets at the root of notches
- Using materials with higher elasticity
If the surface crack causing fracture in a brittle material is made twice as deep, the fracture strength will:
- decrease by a factor of √2
- decrease by a factor of 2
- decrease by a factor of
- No change
Eutectoid point of Fe-Fe3C (Iron-Iron carbide) phase diagram is represented by:
- 0.76% carbon (approximate) and 1147°C (approximate)
- 4.3% carbon (approximate) and 1147°C (approximate)
- 0.76% carbon (approximate) and 727°C (approximate)
- 4.3% carbon (approximate) and 727°C (approximate)
In which heat treatment process steel can achieve highest strength with extremely hard state:
- quenched steel
- tempered steel
- annealed steel
- normalized steel
Which of the following heat treatment processes is primarily used to relieve internal stresses in materials?
- Quenching
- Annealing
- Tempering
- Normalizing
Tempering of quenched martensitic steel is necessary to improve the:
- Hardness of the metal
- Surface texture of the metal
- Corrosion resistance of the metal
- Ductility of the metal
Which of the following phases is NOT a constituent of a eutectic iron-carbon alloy with a composition of about 4.3% carbon?
- Austenite
- Cementite
- Ferrite
- Ledeburite
The case hardening technique suitable for steels with very low carbon content:
- Cyaniding
- Induction hardening
- Electron beam hardening
- Flame hardening
Tempering is done for:
- Increasing hardness
- Increasing toughness
- Increasing brittleness
- Increasing melting point
During cooling, the complete transformation of austenite takes place from liquid state:
- at 723°C
- just above 723°C
- just below 723°C
- At 1130°C
Which of the following phase will be resulted when the transformation temperature of steel is more than 750 °C?
- Austenite
- Pearlite
- Bainite
- martensite
The solid solution formed when carbon atoms are absorbed into face centred cubic structure of iron is called.
- Austenite
- Ferrite
- Cementite
- Martensite
The preferred choice of the steel material for cryogenic application is:
- Ferrite
- Austenitic
- Martensite
- All of the above
What is the minimum percent of Carbon in Iron-Carbon system to define a cast iron?
- 0.5%
- 0.8%
- 1.2%
- 2.0%
Which one of the following represents the energy gap of Silicon (Si)?
- 2.1 eV
- 1.1 eV
- 4.4 eV
- 3.4 cV
Which of the following metals has the highest bond energy?
- Iron
- Magnesium
- Silver
- Tungsten
Wrought iron is a product of:
- Cupola
- Bessemer converter
- Puddling furnace
- Blast furnace
Major constituent of the gun metal is:
- Copper
- Nickel
- Iron
- Zinc
Which mechanical property of a material is defined as its ability to withstand pulling or tensile forces without fracture?
- Compressive Strength
- Hardness
- Tensile Strength
- Creep Resistance
Explanation:
- Tensile Strength is the maximum stress a material can withstand while being stretched or pulled before necking (where the cross-section starts to significantly contract) and fracture occur. It is a key parameter from a tensile test.
- Compressive Strength relates to resisting pushing forces.
- Hardness is resistance to surface indentation.
- Creep Resistance is the ability to resist slow deformation under constant load over time.
The ability of a material to be drawn into wires is known as:
- Malleability
- Toughness
- Ductility
- Brittleness
Explanation:
- Ductility is the property that allows a material to be deformed plastically under tensile stress without fracture; this is what enables drawing into wires.
- Malleability is similar but refers to deformation under compressive stress (e.g., rolling into sheets).
- Toughness is the ability to absorb energy and plastically deform without fracturing.
- Brittleness is the lack of ductility.
***
Which property represents the total area under the stress-strain curve of a material?
- Ductility
- Hardness
- Toughness
- Yield Strength
Explanation:
- Toughness is a measure of the material’s ability to absorb energy up to the point of fracture. The total area under the engineering stress-strain curve represents the energy absorbed per unit volume, which is the modulus of toughness.
- Ductility is measured by percent elongation or reduction in area.
- Hardness is measured by indentation tests.
- Yield Strength is a specific point on the stress-strain curve.
***
The failure of a material under repeated or fluctuating stresses, even if they are below the yield strength, is called:
- Creep
- Brittle Fracture
- Fatigue
- Plastic Deformation
Explanation:
- Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and often below the yield stress limit.
- Creep is time-dependent deformation under a constant load at high temperatures.
- Brittle Fracture is sudden failure with little plastic deformation.
***
A material that shatters or fractures with little or no plastic deformation is described as:
- Ductile
- Tough
- Brittle
- Malleable
Explanation:
- Brittleness is the lack of ductility. A brittle material fractures suddenly under stress with negligible plastic deformation. Examples include cast iron, glass, and ceramics.
- Ductile and Malleable materials undergo significant plastic deformation.
- A Tough material can be ductile and is characterized by its ability to deform plastically and absorb energy.
***
The slow, time-dependent, and permanent deformation of a material under a constant static load at elevated temperatures is known as:
- Fatigue
- Yielding
- Creep
- Elastic Deformation
Explanation:
- Creep becomes a critical design consideration for components operating at high temperatures, such as turbine blades, steam pipes, and nuclear reactor components. The deformation continues to increase over time while the stress remains constant.
- Fatigue is caused by cyclic loads.
- Yielding is the onset of plastic deformation under a single load.
- Elastic Deformation is temporary and recovered upon unloading.
***
Which property is measured by pressing an indenter into the surface of a material?
- Impact Strength
- Tensile Strength
- Hardness
- Ductility
Explanation:
- Hardness is a measure of a material’s resistance to localized plastic deformation (e.g., a small dent or scratch). Common tests include Brinell, Rockwell, and Vickers, which use different indenters and scales.
- Impact Strength is measured by a notched-bar impact test (e.g., Charpy or Izod).
- Tensile Strength is measured by pulling a specimen.
- Ductility is derived from the tensile test.
***
The ability of a material to withstand suddenly applied loads is known as:
- Fatigue Strength
- Creep Strength
- Impact Strength
- Compressive Strength
Explanation:
- Impact Strength or toughness is the ability of a material to absorb energy and resist shock loading. It is typically measured using a pendulum impact test machine on a notched specimen (Charpy or Izod test).
- Fatigue Strength is the stress level a material can endure for a specified number of cyclic loads.
- Creep Strength is the stress that causes a specified creep rate at a high temperature.
- Compressive Strength is the capacity to withstand axially directed pushing forces.
Steels are primarily classified based on their:
- Density and electrical conductivity
- Melting point and thermal expansion
- Carbon content and alloying elements
- Color and market price
Explanation:
- The fundamental classification of steel is determined by its chemical composition, most importantly the percentage of carbon, which defines its basic category (e.g., low, medium, high carbon).
- Further classification is based on the presence and percentage of other alloying elements (like Chromium, Nickel, Molybdenum) which gives rise to alloy steels.
- Properties like density and melting point do not vary enough for classification, while color and price are not technical criteria.
***
Mild steel is a type of low-carbon steel typically containing carbon in the range of:
- 0.0% to 0.05%
- 0.05% to 0.25%
- 0.25% to 0.50%
- 0.50% to 0.80%
Explanation:
- Mild steel, also known as low-carbon steel, is characterized by a carbon content between approximately 0.05% and 0.25%.
- This low carbon content makes it malleable, ductile, and easy to weld, but it cannot be hardened significantly by heat treatment. It is the most common form of steel used in construction and general fabrication.
***
The primary purpose of adding alloying elements like Chromium and Nickel to create alloy steels is to:
- Reduce the overall cost of the material
- Make the steel easier to machine in all conditions
- Enhance mechanical properties and tailor performance (e.g., hardness, corrosion resistance)
- Lower the melting point of the steel
Explanation:
- Alloying elements are added to improve specific properties that cannot be achieved with plain carbon steels.
- For example, Chromium improves hardness, wear resistance, and corrosion resistance (key for stainless steels). Nickel increases toughness and strength. Molybdenum improves high-temperature strength.
- Alloy steels are often more expensive and can sometimes be more difficult to machine, which is not the primary goal.
***
Which of the following is a key importance of the heat treatment process on steel?
- To change the basic chemical composition of the steel
- To permanently increase the weight and density of the component
- To alter the microstructure and thus obtain desired mechanical properties
- To make the steel rust-proof without any additional elements
Explanation:
- The core importance of heat treatment is its ability to precisely control the microstructure of the steel (e.g., forming martensite, spheroidite, etc.).
- By controlling the microstructure through controlled heating and cooling, we can enhance properties like hardness, strength, ductility, toughness, and wear resistance without altering the chemical composition.
- Heat treatment cannot add new elements like chromium for rust prevention; that is a function of the steel’s composition.
***
A plain carbon steel with 0.40% carbon content is most likely to be classified as:
- Low-carbon steel (Mild steel)
- Medium-carbon steel
- High-carbon steel
- Tool steel
Explanation:
- The general classification is:
- Mild / Low-carbon steel: Up to 0.25% C
- Medium-carbon steel: 0.25% to 0.50% C
- High-carbon steel: 0.50% to 0.80% C (and above for tool steels)
- With 0.40% carbon, it falls squarely in the medium-carbon range. This steel can be effectively heat treated (e.g., quenched and tempered) to achieve good strength and toughness, making it suitable for shafts, gears, and rails.
***
The main reason mild steel is generally NOT hardened by heat treatment is:
- It has a very high melting point
- It is always used in painted conditions
- Its low carbon content is insufficient to form hard martensite
- It is an alloy steel by definition
Explanation:
- The ability to form hard martensite during quenching depends on the carbon content dissolved in the austenite phase before cooling.
- Mild steel has very low carbon content (typically < 0.25%). This amount is insufficient to cause a significant hardening effect upon quenching. The resulting structure lacks the hardness associated with martensite.
- Medium and high-carbon steels have enough carbon to become very hard when quenched.
Which heat treatment process is primarily used to soften a hardened steel to improve its toughness and reduce its brittleness?
- Annealing
- Hardening
- Tempering
- Carburizing
Explanation:
- Tempering is a process performed after hardening. It involves reheating the hardened steel to a temperature below the lower critical temperature and then cooling it. This reduces internal stresses, decreases hardness slightly, and dramatically increases toughness and ductility.
- Annealing also softens metal but is done for different reasons (like relieving stress or improving machinability) and involves slower cooling.
- Hardening increases hardness and brittleness.
- Carburizing is a surface hardening process.
***
The process of heating steel above its upper critical temperature, holding it there for a period, and then cooling it in still air is called:
- Annealing
- Normalizing
- Tempering
- Quenching
Explanation:
- Normalizing involves air cooling, which is faster than the furnace cooling used in annealing. This results in a finer pearlitic structure, making the steel stronger and harder than annealed steel.
- Annealing uses slow furnace cooling to produce a coarse pearlitic structure that is softer.
- Tempering is a lower-temperature process done after hardening.
- Quenching is the rapid cooling (e.g., in water or oil) used in the hardening process.
***
Which of the following processes is used to increase the surface hardness of a low-carbon steel by increasing its surface carbon content?
- Nitriding
- Tempering
- Carburizing
- Annealing
Explanation:
- Carburizing is a case-hardening process where steel is heated in a carbon-rich environment (solid, liquid, or gas) above its austenitizing temperature. Carbon atoms diffuse into the surface, creating a high-carbon “case” that can be hardened by subsequent quenching.
- Nitriding also hardens the surface but uses nitrogen and does not require quenching.
- Tempering and Annealing are processes that soften steel.
***
The process that introduces both carbon and nitrogen into the surface of steel to enhance wear resistance is known as:
- Carburizing
- Nitriding
- Cyaniding
- Normalizing
Explanation:
- Cyaniding involves heating the steel in a molten salt bath containing sodium cyanide (NaCN). The active carbon and nitrogen atoms released from the cyanide diffuse into the steel surface, creating a hard, wear-resistant case.
- Carburizing adds only carbon.
- Nitriding adds only nitrogen.
- Normalizing is a bulk heat treatment process, not a surface hardening one.
***
Which of the following processes is performed at the highest temperature relative to the steel’s critical temperature?
- Tempering
- Nitriding
- Full Annealing
- Cyaniding
Explanation:
- Full Annealing requires heating the steel to approximately 30-50°C above its upper critical temperature (A3 line) to achieve complete austenitization.
- Tempering is done at much lower temperatures (150-650°C), below the lower critical temperature (A1).
- Nitriding is performed in the range of 495-565°C, also below A1.
- Cyaniding is typically done between 760-850°C, which is above A1 but often below the upper critical temperature for many steels.
***
The primary purpose of the Austempering process is to:
- Produce a fully martensitic structure
- Increase the carbon content on the surface
- Obtain a bainitic structure to achieve high strength with good ductility and minimal distortion
- Relieve internal stresses from casting
Explanation:
- Austempering is an isothermal heat treatment. Steel is austenitized, quenched to a temperature above the martensite start (Ms) point (usually in a salt bath), and held until the austenite transforms to bainite. This avoids the formation of brittle martensite and reduces the risk of quench cracking and distortion associated with conventional hardening.
- Conventional hardening aims for martensite.
- Carburizing increases surface carbon.
- Stress relieving is a separate, low-temperature process.
***
In the context of the Iron-Carbon diagram, hardening of steel is possible because of the formation of which metastable phase upon rapid cooling (quenching)?
- Austenite
- Cementite
- Ferrite
- Martensite
Explanation:
- Martensite is a super-saturated, interstitial solid solution of carbon in iron with a body-centered tetragonal (BCT) structure. It is extremely hard and brittle. It forms when austenite is cooled so rapidly that the carbon atoms do not have time to diffuse out and form cementite.
- Austenite, Cementite, and Ferrite are all stable or semi-stable phases found under equilibrium cooling conditions.