# Important Short Questions in Material Science – AKTU 2021-22

Providing all units ‘PHASE DIAGRAMS’‘FERROUS ALLOYS‘‘MECHANICAL PROPERTIES‘‘MAGNETIC, DIELECTRIC & SUPERCONDUCTING MATERIALS‘ and ‘NEW MATERIALS‘ Material Science Important short Questions with the solution – AKTU, Last year’s question paper with solutions, and many more study materials that will help students or bachelor’s exam

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Important Questions For Material Science :
*Unit-01     *Unit-02
*Unit-03    *Unit-04
*Unit-05    *Short-Q/Ans
*Question-Paper with solution 21-22 ```

## Unit – 1 (Phase Diagrams)

#### Q1. What do you mean by solid solution ?

Ans.  A solid solution is a solution of one or more solutes in a solvent in a solid state.

#### Q2. What is substitutional solid solution ?

Ans. If the two atoms are similar in size, the solute will randomly substitute for one of the matrix atoms in the crystal lattice. A substitutional solid solution is the name given to this type of structure.

#### Q3. What are the types of substitutional solid solution ?

Ans. Types of substitutional solid solution are as follows :

1. Random substitutional solid solution, and

2. Ordered substitutional solid solution.

#### Q4. What is interstitial solid solution ?

Ans. When a few relatively small atoms accommodate in the interstices between solvent atoms, an interstitial solid solution occurs.

#### Q5. Explain Gibbs phase rule.

Ans. Gibbs established a relationship between degree of freedom, the number of components present, and the number of phases in equilibrium.

Mathematically,

P + F =C + n

#### Q6. What is phase diagram ?

Ans. A phase diagram is a graphical representation of the phases that exist in a material system at different temperatures, pressures, and compositions.

#### Q7. Write down the types of phase diagram.

Ans. Types of phase diagram are as follows :

1. Unary phase diagram,

2. Binary phase diagram, and

3. Ternary phase diagram.

#### Q8. What are the informations required for interpretation of phase diagrams ?

Ans. Information required for interpretation of phase diagrams are:

1. Phases present.

2. Composition of phases.

3. Fraction of phases.

#### Q9. What is an isomorphous system ?

Ans. Isomorphous systems have two metals that are mutually soluble in any proportion, at any temperature, and in every state of matter.

#### Q10. What is eutectic phase diagram ?

Ans. When the melting points of the two components are not significantly different and there is only partial or minimal solid solubility between them, the phase diagram is referred to as a eutectic phase diagram.

#### Q11. What do you understand by eutectoid reaction ?

Ans. The eutectoid reaction occurs when a solid phase cools and transforms into two additional solid phases.

#### Q12. What is peritectic phase diagram?

Ans. When the melting points of two components are too far apart, a peritectic phase diagram is formed. The gold-lead system is an example of a peritectic phase diagram.

#### Q13. What is the use of lever rule ?

Ans. It is used for the estimation of:

1. The fraction of a proeutectic phase.

2. The fraction of the eutectic mixture.

3. The fraction of phase that form eutectic mixture.

#### Q14. Give the limitation of lever rule.

Ans. The lever rule does not apply at eutectic or peritectic temperatures.

#### Q15. What is tie-line rule ?

Ans. In a binary phase diagram, the tie-line rule is used to identify the composition of two coexisting phases. The tie-line is a horizontal line drawn within the two phase region at the temperature of interest.

#### Q16. What is invariant reaction ?

Ans. When a liquid of eutectic composition is steadily chilled to eutectic temperature, the single liquid phase changes into solid forms simultaneously. This is referred to as an invariant reaction.

## Unit – 2 (Ferrous Alloys)

#### Q1. Write down the significance of iron-carbon equilibrium diagram.

Ans. The iron-carbon diagram is useful for studying the behaviour of iron and iron alloys. It is the foundation of commercial steels and cast irons, and it can influence the behaviour of the majority of complex alloy steels.

#### Q2. What are various solid phases in iron-carbon equilibrium diagram?

Ans. Following are the various solid phase in iron-carbon equilibrium diagram:

1. a-Ferrite,

2. Austenite,

3. Cementite, and

4. δ-ferrite.

#### Q3. What is diffusion ?

Ans. Diffusion is the movement of atoms and molecules to new locations within a material as a result of heat agitation, resulting in compositional uniformity.

#### Q4. What is recrystallization temperature ?

Ans. Recrystallization temperature is the lowest temperature at which complete recrystallization will occur in approximately one hour for a specific alloy.

#### Q5. What is TTT diagram ?

Ans. The Temperature-Time-Transformation diagram depicts the relationship between the beginning and end of the production of various microstructures.

#### Q6. Define ‘critical cooling rate’ in TTT diagram with neat sketch.

Ans.The snout of the curve in a TTT diagram represents the shortest time required for a specific transformation. The critical cooling rate is defined as the slope of the line that passes through this nose (C-curve).

#### Q7. Define term pearlite.

Ans. Pearlite is made up of 87 to 13 weight ratio alternate layers of ferrite and cementite. The delayed cooling of austenite results in the development of pearlite.

#### Q8. Define term martensite.

Ans. Martensite is generated in carbon steels by rapidly and continuously cooling austenite to temperatures ranging from 205°C to 315°C, or even lower. Martensite crystal structure is tetragonal.

#### Q9. What are the applications of low carbon steel ?

Ans. Following are the applications of low carbon steel :

1. Automobile body components,

2. Structural shapes such as I-beam, channels etc.,

3. Pipelines, buildings, bridges, and

4. Tincans.

#### Q10. Where do we use medium carbon steels ?

Ans. Medium carbon steels are used in :

1. Railway wheels and tracks,

2. Gears, ·

3. Crankshafts,

4. Machine parts, and

5. High strength structural components.

#### Q11. What are the applications of high carbon steels ?

Ans. Application of high carbon steels are as follows :

1. Cutting tools and dies for forming and shaping materials,

2. Hacksaw blades, and

3. Springs.

#### Q12. What are basic types of cast iron ?

Ans. Types of cast iron are as follows :

1. Grey cast iron,

2. White cast iron,

3. . Ductile cast iron, and

4. Malleable cast iron.

#### Q13. Write down the properties of cast iron.

Ans. Properties of cast iron are as follows :

1. It has good hardness due to presence of carbon percentage.

2. It can be machine easily due to good machinability.

3. It has very good rigidity.

#### Q14. How is cast iron produced ?

Ans. Cast iron is made by melting pig iron with coke and limestone in a cupola furnace, which uses coke as fuel and limestone as a flux.

#### Q15. Define an alloy.

Ans. An alloy is a metallic material made up of two or more elements.

#### Q16. What is Fick’s first law ?

Ans. Fick’s first law describes the rate at which diffusion occurs. This

states that,

Where,              dn = Amount of metal in kg that crosses a plane

normal to the direction of diffusion,

dc/dx, = Slope of concentration gradient,

D = Diffusion coefficient,

a = Area of plane across which diffusion takes place,

and

dt = Duration of diffusion.

#### Q17. What is Fick’s second law ?

Ans. Fick’s second law explains the time dependency of concentration, which Fick’s first law does not.

#### Q18. What is phase transformation ?

Ans. Phase transformation is significant in material processing since it involves some microstructure modification.

#### Q19. Why yield point occurs in low carbon steel ?

Ans. The presence of interstitial carbon and nitrogen atoms causes the yield point phenomenon in low carbon steel.

## Unit – 3 (Mechanical Properties)

#### Q1. What are the different ways of dislocation strengthening ?

Ans. Following are the three ways of dislocation strengthening :

1. Strengthening by grain size reduction,

2. Solid solution strengthening, and

3. Strain hardening.

#### Q2. Explain the edge dislocation in short.

Ans. Edge dislocation is a defect caused by the addition of an extra partial plane of atoms to the crystal.

Ans.

#### Q4. Define the term ductility.

Ans. Ductility is the property of a material that allows it to be pulled out lengthwise to a smaller portion under the action of tensile stress.

#### Q5. What do you understand by creep ?

Ans. Creep is the time-dependent permanent distortion that happens when most materials are stressed.

#### Q6. Draw the stress strain diagram for brittle materials and explain.

Ans. Fig.  shows the stress strain diagram for brittle materials, in which the axial strain are plotted along x-axis and corresponding stresses are plotted along y-axis.

#### Q7. Define fatigue life.

Ans. Fatigue life is defined as the number of stress cycles that the standard specimen can complete before the first fatigue crack appears during the test.

#### Q8. What is fatigue phenomenon ?

Ans. Fatigue is a type of failure that occurs when a structure (such as bridges, aircraft, and machine components) is subjected to dynamic and fluctuating loads.

#### Q9. Write down some fatigue properties.

Ans. Some fatigue properties are as follows :

1. Fatigue life scatter tends to increase the longer fatigue lives.

2. Damage is cumulative.

#### Q10. What is the need of fatigue testing?

Ans. Fatigue tests are carried out in laboratories to measure a material’s ability to endure repeated applied stress.

#### Q11. Define the term strain hardening.

Ans. Strain hardening is the plastic deformation-based strengthening of a metal or polymer.

#### Q12. Write down the factors on which critical stress intensity factor depends.

Ans. Following are the factors on which critical stress intensity factor depends :

1. Sample geometry,

2. Size and location of the crack,

3. Magnitude of load, and

4. Distribution of load.

#### Q13. What are the drawbacks of Brinell hardness test ?

Ans. Drawbacks of Brinell hardness test are as follows :

1. Sinking effect, and

2. Piling-up effect.

#### Q14. A hardened steel ball of0.50 cm diameter is used to indent a steel specimen in Brinell hardness test. Diameter of indentation measured by an optical microscope of magnification 10 X is observed to be 32.5 mm. Calculate Brinell hardness number of the steel specimen.

Ans. Given: D = 0.50 cm= 5 mm,’a = 32.5 mm

To Find: Brinell hardness number,of the steel specimen.

#### Q15. Write some creep resistant materials.

Ans. Some creep resistant materials are as follows :

1. Refractories,

2. Tungsten based alloys,

3. Cobalt based alloys, and

4. Monocrystal titanium.

#### Q16. What do you understand by yield strength ?

Ans. The tension at which a material begins to bend plastically is characterised as yield strength.

#### Q17. Define hardness.

Ans. The term hardness refers to the ability of a metal to withstand abrasion, indentation (or penetration), and scratching by harder bodies.

#### Q18. What is dislocation ?

Ans. Dislocation is a linear disruption of the atomic arrangement that can occur relatively easily on the slip plane through the crystal.

#### Q19. Differentiate between toughness and resilience. Also define the endurance limit.

Ans. Difference between Toughness and Resilience :

Endurance Limit : The limiting stress value below which a load can be applied repeatedly indefinitely many times.

## Unit – 4 (Magnetic Dielectric and Superconducting Materials)

#### Q1. What do you mean by amorphous materials ?

Ans. Amorphous materials are those that have a random and irregular arrangement of atoms over a relatively long atomic distance.

#### Q2. Define the term ferrites.

Ans. Ferrites are magnetic ceramic materials made by mixing iron oxide (Fe2O3) with other oxides and carbonates in the powdered form.

#### Q3. What are ferromagnetic materials ?

Ans. Ferromagnetic materials are those that have the ability to be highly magnetized. Ferromagnetic elements include iron, cobalt, and nickel.

#### Q4. What is diamagnetism ?

Ans. Diamagnetism is the phenomena of a material’s weak, negative, repulsive reaction to an applied magnetic field. Diamagnetic materials have a low magnetic susceptibility.

#### Q5. What is paramagnetism ?

Ans. Paramagnetism is the phenomenon of a material’s weak, positive, attracting reaction to an applied magnetic field. Positive magnetic susceptibility is low in paramagnetic materials.

#### Q6. Define magnetic domain.

Ans. Magnetic moments of neighbouring atoms tend to point in the same direction due to quantum mechanical exchange forces. A magnetic domain is a collection of neighbouring atoms that all point in the same direction.

#### Q7. What are the different types of energies associated with ferromagnetic materials ?

Ans. Different types of energies associated with ferromagnetic materials are as follows :

1. Exchange energy,

2. Magnetostatic energy,

3. Magnetocrystalline anisotropy energy,

4. Domain wall energy, and

5. Magnetostrictive energy.

Ans.

#### Q9. What is dielectric ?

Ans. A dielectric substance is one that is electrically insulating (nonmetallic) and has or can be manufactured to have an electric dipole structure, which means that positive and negative electrically charged entities are separated on a molecular or atomic level.

#### Q10. Define polarization.

Ans. The alignment of permanent or induced atomic or molecule dipole moments with an externally applied electric field is referred to as polarization.

#### Q11. Name the different types of polarization.

Ans. Following are the types of polarization :

1. Electronic polarization,

2. Ionic polarization, and

3. Orientation polarization.

#### Q12. Write Langevin-Debye equation and also write its importance.

Ans. Langevin-Debye Equation :

Importance : This equation has great importance in interpreting the structure of a polar dielectric.

#### Q13. What is dielectric breakdown ?

Ans. The failure of a dielectric to sustain applied electrical stress is known as dielectric breakdown (electric field). It might be full (as in a spark breakdown) or partial (as in corona or a series of partial discharges).

#### Q14. What do you understand by insulating materials ?

Ans. Insulating materials are any materials that slow or completely halt the movement of heat, electricity, or sound through them.

#### Q15. What are the types of insulating materials ?

Ans. Types of insulating materials are as follows:

1. Thermal insulators, e.g., Asbestos, cork, cellular rubber etc.

2. Electrical insulators, e.g., Glass, cotton, bakelite etc.

3. Sound insulators, e.g., Acoustic boards, acoustic plaster etc.

#### Q16. What do you mean by ferroelectric material ?

Ans. Ferroelectric materials are those that possess ferroelectric characteristics.

#### Q17. What is Meissner effect ?

Ans. When a superconductor is cooled under a magnetic field below its critical temperature, the lines of induction are expelled from the material. This is known as the Meissner effect.

#### Q18. Write any two applications of dielectric materials.

OR

#### State some applications of dielectric material.

Ans. Dielectric materials are used in following devices:

1. Capacitors, resistors and strain gauges.

2. Piezoelectric and electro-optic devices.

## Unit – 5 (New Materials)

#### Q1. What is a ceramic material ? Give any two examples.

Ans. Ceramic Material: Ceramics Tie the composite of metallic and non-metallic elements with primarily ionic interatomic bonding. These materials’ desirable qualities are often obtained by a high temperature heat treatment technique.

Examples : Clay products, abrasives, etc.

#### Q2. Write down any four properties of ceramic materials.

Ans. Properties of ceramic materials are as follows :

1. They are very hard and brittle in nature.

2. They have low electrical and thermal conductivity.

3. They are relatively stiff and strong as compared to metals.

4. They are more resistant to high temperatures.

#### Q3. Write down the types of matrix materials.

Ans. Types of matrix materials are as follows :

1. Ceramic matrix,

2. Metal matrix, and

3. Polymer matrix.

#### Q4. What are the applications of matrix materials ?

Ans. Following are the applications of matrix materials :

1. In electrical molding,

2. In decorative laminates,

3. In high performance cookware, and

4. In sealants and gaskets.

#### Q5. What is FRP ?

Ans. Fiber reinforced polymer is a polymer matrix reinforced with fibres composite material.

#### Q6. Write down three examples of FRPs.

Ans. Examples of FRPs are as follows :

1. Glass,

2. Carbon, and

3. Aramid.

#### Q7. Write down the advantages of composites.

Ans. Advantages of composites are as follows :

1. Light weight,

2. High strength,

3. Strength related to weight,

4. Corrosion resistance, and

5. Non-magnetic.

#### Q8. Give the classification of ceramics.

Ans. Ceramic materials can be classified as :

1. Glasses,

2. Clay products,

3. Refractories,

4. Abrasives,

5. Cements, and

#### Q9. Write down the properties of ceramics.

Ans. Properties of ceramics are as follows :

1. Ceramic materials are relatively stiff and strong as compared to the metals.

2. Ceramic materials are very hard and brittle in nature.

3. These have low electrical and heat conductivity.

#### Q10. What are the applications of nanomaterials ?

Ans. Applications of nanomaterials are as follows :

1. In microelectronics,

2. Machine tools,

3. High power magnets,

4. Motor vehicles and aircraft, and

5. Cosmetics.

#### Q11. What is nanomaterial ?

Ans. A nanomaterial is a material with any external dimension in the nanoscale, as well as internal or surface structure in the nanoscale (length range approximately from 1 nm to 100 nm).

#### Q12. Write down the properties of nanomaterials.

Ans. Properties of nano materials are as follows :

1. Chemically very active.

2. Erosion resistant.

3. Ductile at high temperature.

#### Q13. State the advantages of nanomaterials.

Ans. Advantages of nano materials are as follows :

1. They have ultrafine grain structures.

2. They have high strength and hardness.

#### Q14. What is metallic glass ?

Ans. Metallic glass, also known as glassy metal or amorphous metal, is a solid metallic substance, typically an alloy, having a disordered atomic size structure.

#### Q15. Write down the applications of metallic glasses.

Ans. Applications of metallic glasses are as follows:

1. They are used to create razor blades and other types of springs due of their great strength, ductility, and corrosion resistance.

2. Metallic glasses are utilised in tape recorder heads, cores of high power transformers, and metallic shields due to their soft magnetic characteristics.

#### Q16. What is shape memory alloy ?

Ans. A form When heated, a memory alloy can be deformed but then returns to its pre-deformed (remembered) shape. Memory metal, memory alloy, smart metal, smart alloy, and muscle wire are some other names for it.

#### Q17. Write down the application of NiTi alloys.

Ans. Application of NiTi alloys are as follows :

1. As it changes shape, it can activate a switch or a variable resistor, allowing it to be utilised as a temperature control system.

2. Because of its extreme flexibility and mechanical memory, it has been employed in cell phone technology as a retractable antenna or microphone boom.

#### Q18. What do you understand by carbon nanotubes ?

Ans. Carbon nanotubes are hollow cylindrical tubes made of carbon. Carbon nanotubes can range in length from several micrometres to millimetres, and their diameter can range from 1 to 20 nm.

#### Q19. What is. a composite material ? Give any two examples.

Ans. Composite Material : It can be defined as the joining of two or more materials to make a new one.

Examples : Concrete, Cements etc.

#### Q20. What are refractory materials ? Give some examples.

Ans. Refractory Material : These are heat-resistant materials that can tolerate high temperatures, have adequate mechanical strength, are heat-resistant, and have a consistent volume.

Examples : Graphite, thoria, zirconia, fireclay bricks.