Engineering Materials – Mechanical Engineering Optional PYQs (1995–2026)

Here are all 102 Engineering Materials questions asked in UPSC Mechanical Engineering Optional Paper I from 1995 to 2026, arranged under the 4 topics of the official syllabus. Within each topic the latest questions come first.

Each question ends with a code such as [2024/15m/3b] – the year, the marks, the word limit (where UPSC set one) and the question number in the paper.

2.1] Structure of solids

34 questions

1. Why is grain size important in polycrystalline materials? How is it estimated? (i) Determine the ASTM grain size number of a metal specimen if 75 grains/square inch are measured at a magnification of 100×. (ii) For the same specimen, how many grains/inch${}^2$ can be estimated at a magnification of 60×? [2026/10m/1c]

2. With the help of a neat diagram, illustrate the microstructures of various phases of steel and exhibit the presence of the following: (i) Ferrite (ii) Austenite (iii) Cementite (iv) Pearlite. [2025/10m/1d]

3. Calculate the packing efficiency and packing density of carbon if mass of carbon atom is $1.992\times {10}^{-26}kg$ and unit cell side ($a$) is $3.57\times {10}^{-10}m$. Assume crystal structure of carbon as diamond cubic. [2024/10m/2c]

4. What is the importance of the atomic packing factor? Compute the atomic packing factor for the FCC crystal structure. [2023/10m/1d]

5. What is Atomic Packing Factor of a crystal structure? Calculate the atomic packing factor of aluminium assuming atoms to be of spherical shape with atomic radius ‘R’. [2022/15m/2b]

6. Find out the value of atomic packing factor for the FCC crystal structure. Calculate the radius of an iridium (Ir) atom, given that Ir has an FCC crystal structure, a density of $22.4g/c{m}^3$ and an atomic weight of 192.2 g/mol. [Avogadro’s number $\left(N_A\right)=6.022\times {10}^{23}$ atoms/mol]. [2021/15m/4a]

7. Draw the following crystallographic planes in cubic unit cell: (i) (101) (ii) $\left(1\bar{1}0\right)$ (iii) (221) [2020/10m/3c]

8. Draw a neatly labelled iron-iron carbide phase diagram indicating salient regions, phases and reactions. [2018/10m/1e]

9. Describe different crystal systems in Materials. [2014/10m/1c]

10. A hypoeutectoid plain c-steel is heated to 1540°C and then cooled slowly to 725°C. What is the percentage of ferrite and austenite in steel after the process? Mark the process on Iron-carbon diagram. [2012/12m/1c]

11. How ductility of structural steel is evaluated from static tension test? What is the effect of gauge length on the value of ductility? [2011/10m/1d]

12. (i) Differentiate between point defects and line defects in a crystalline solid. (ii) With a neat diagram show two types of line defects. How are they formed? [2011/15m/4c]

13. Distinguish between Eutectoid and Eutectic, in the case of Fe – C system. Give the composition and the maximum temperature at which eutectoid and eutectic are formed. [2010/12m/1d]

14. Explain the transformation of iron from BCC to FCC. What properties change when iron changes from BCC structure to FCC structure? [2010/20m/4c]

15. In an orthogonal crystal structure with lattice parameters $a\ne b\ne c$, draw the direction $\left[2\bar{1}2\right]$. [2009/10m/1c(i)]

16. Show that in a hexagonal close-packed structure, atomic packing factor is 0.74. Take dimension $c=1.633a$. [2009/10m/1c(ii)]

17. (i) What alloys are commonly die-cast? Write the composition, properties and uses of carbide cutting tools. (ii) Define unit cell. Calculate the linear density of the [100] direction for bcc. (iii) Draw T-T-T diagram for eutectoid steel. What is a graphite? [2008/20m/200w/1d]

18. (i) With the help of a neat sketch, explain the following terms: Crystallographic axes, Primitives and Interfacial angles. (ii) Compare BCC and FCC structures. (iii) What is solid solution? Explain with the help of neat sketches the different types of solid solutions. [2007/20m/1d]

19. Explain the method of controlling the grain size in a polycrystalline material. [2007/15m/4a]

20. What is a slip system? What is its significance? [2005/10m/1d(i)]

21. Explain the term crystallographic anisotropy. [2005/10m/1d(ii)]

22. State: (i) Gibbs phase rule and lever rule (ii) Isomorphous system (iii) Pertiectic reaction in steel. [2003/15m/4a]

23. Explain: (i) Strain Aging (ii) Eutectoid steel (iii) Dead Mild steel. [2003/15m/4b]

24. Differentiate among pearlite, ferrite, martensite and austenite. [2003/15m/4d]

25. For engineering materials; differentiate between the following: (i) A system and state (ii) Extrinsic and intrinsic properties (iii) Degree of freedom and constraint (iv) Phase and component. [2002/10m/4a]

26. Differentiate between the following (i) Homogeneous nucleation and heterogeneous nucleation (ii) Nucleation and growth (iii) Embryos and nuclei (iv) Supercooling and sublimation. [2002/20m/4b]

27. Differentiate between: (i) Directional and non-directional bond (ii) Bond length and bond energy (iii) Ionic bond and covalent bond (iv) Metallic bond and hydrogen bond. [2002/20m/4d]

28. With the help of neat sketches, differentiate clearly between interstitial and substitutional solid solutions. Comment on Fe – C and Au – Ag solid solutions. [2001/30m/4a]

29. What do you understand by atomic packing factor? Determine atomic packing factor for BCC structure. [2001/10m/4b]

30. Explain the mechanisms of (i) Discontinuous yielding in mild steel when tested under tension (ii) Hysteresis loop for a ductile material when subjected to a stress cycle of loading in tension to plastic state unloading, loading in compression and then unloading. [2001/20m/4c]

31. Differentiate between (i) Solid solution and Eutectoid and (ii) Eutectic and Eutectoid. [2000/20m/4a]

32. (i) Mention the crystal structures for the following elements: Iron; Chromium; tungsten; Nickel and Zinc. (ii) Sketch the following for an FCC structure: (iii) and <110> [?]. [1997/20m/200w/5a]

33. Sketch and discuss the defects in a lattice structure of a crystalline material. [1996/20m/200w/5a]

34. How does grain size in a poly crystalline solid affect the strength of the solid? What happens to grain size in (i) forging (ii) rolling. [1995/20m/200w/5a]

2.2] Ferrous and non-ferrous materials

19 questions

1. Compare different types of cast iron in respect of (i) form of carbon, (ii) microstructure and (iii) mechanical properties. [2024/10m/3c]

2. Discuss three reasons why ferrous alloys are used so extensively and also discuss three characteristics of ferrous alloys that limit their utilization. [2023/10m/2c]

3. What are cast irons? On the basis of microstructure, briefly explain why gray iron is brittle and weak in tension. Compare gray and malleable cast irons with respect to the following: (i) Composition and heat treatment (ii) Microstructure (iii) Mechanical characteristics (iv) Applications. [2018/10m/3b]

4. Write the composition of low, medium and high carbon steels and their applications. [2016/10m/1d]

5. What is the composition of maraging steel? What are its uses? Give the composition of austenitic stainless steel and state some of its applications. [2015/10m/3c]

6. Compare the main characteristics with regard to their hardening and magnetic properties of various stainless steels. [2012/10m/3c]

7. Classify stainless steels based on the metallurgical considerations. Write main characteristics of each class of stainless steels. [2011/10m/1f]

8. What is Tin Babbitt? What is the composition and major application of this alloy? How is it different from other Babbitts? [2010/20m/4a]

9. (i) What alloys are commonly die-cast? Write the composition, properties and uses of carbide cutting tools. (ii) Define unit cell. Calculate the linear density of the [100] direction for bcc. (iii) Draw T-T-T diagram for eutectoid steel. What is a graphite? [2008/20m/200w/1d]

10. What do you mean by ‘stellite’? What are the important properties possessed by this material? Write down the uses of stellite in the engineering applications. [2007/15m/4b]

11. What are the various types of plain carbon steel? List important mechanical properties and their common industrial applications. [2006/20m/1d]

12. What are the important properties possessed by stainless steel? [2006/15m/4a(i)]

13. Give composition and uses of following stainless steels: (1) Ferritic stainless steel (2) Martensitic stainless steel (3) Austenitic stainless steel. [2006/15m/4a(ii)]

14. What elements are generally alloyed to aluminum? What are their effects? [2005/10m/4c]

15. Give composition and application of following: (i) Stellite (ii) Phosphor Bronze (iii) Muntz Metal (iv) Alnico. [2003/20m/1d]

16. What do you mean by ‘plain carbon steels’ and ‘alloy steels’? Discuss the effect of addition of following elements in making alloy steels (i) Chromium (ii) Nickel (iii) Manganese (iv) Silicon (v) Molybdenum (vi) Vanadium (vii) Tungsten. [2002/20m/1d]

17. Give the composition and applications of following alloys: (i) Maraging steel (ii) Invar (iii) Beryllium bronze (iv) Aluminium bronze. [2001/20m/1d]

18. Give the compositions and applications of Alumel alloy and Nichrome alloy. [2001/10m/4d]

19. Explain the various alloys of copper giving the details of composition of each alloy. [2000/20m/4c]

2.3] Heat-treatment of steels

29 questions

1. What is heat treatment? What is its purpose? Explain different heat treatment processes with the help of common microstructural phases of steel on an Iron-Carbon equilibrium diagram. [2026/10m/2a]

2. Identify the different types of defects and their causes in a steel article after it is hardened. [2025/10m/3c]

3. Explain critical cooling rate using continuous cooling transformation (CCT) diagram and write its importance in hardening heat treatment of alloy steel. [2024/10m/1d]

4. Discuss microstructure and mechanical properties of pearlite, bainite and martensite. [2023/10m/3c]

5. Explain the principle of annealing with the help of Continuous Cooling Transformation (CCT) diagram. Write the purpose and applications of annealing heat treatment. [2022/15m/4b]

6. What is carbon equivalent (CE)? How does the carbon equivalent of a steel affect the hardening heat treatment? [2021/10m/1c]

7. What is the purpose of tempering of hardened steel? Explain the principle of tempering using suitable schematics including heating temperature requirement and microstructural changes. [2021/15m/3a]

8. Define the term hardenability. Which factors affect hardenability? [2020/10m/1d]

9. What are the factors affecting critical cooling rate? [2019/10m/1c]

10. (i) What is normalizing? State clearly its purpose, process and applications. (ii) Compare normalizing and annealing processes. [2019/15m/3b]

11. Summarize the microstructures and mechanical properties of the following microconstituents of iron-carbon alloys in terms of phases present, arrangement of phases and relative mechanical properties: (i) Spheroidite (ii) Fine pearlite (iii) Bainite (iv) Tempered martensite (v) Martensite. [2018/10m/2c]

12. For a eutectoid steel, draw and label continuous cooling transformation (CCT) diagram. Explain normalizing and hardening heat treatment with regard to phase transformation using relevant cooling curves on CCT diagram. [2017/15m/3c]

13. What is critical cooling rate in heat treatment of steels? Write about the significance of critical cooling using TTT diagram. What are the factors affecting critical cooling rate? [2016/20m/2c]

14. What are the advantages of tempering carbon steel? Show with the help of iron-carbon equilibrium diagram, how low, medium and high temperature tempering are done. [2015/10m/1e]

15. What are the advantages of annealing steel? Explain the process of annealing with a sketch of Time – Temperature transformation and ending with spheroidizing. [2015/10m/4c]

16. Describe Austempering of steel with help of TTT diagram. [2014/10m/2b]

17. Differentiate between (i) annealing, and (ii) tempering. Mark the processes on a TTT diagram and bring out the transformations that take place during the process. [2013/10m/1e]

18. Give chemical reactions and temperature ranges in the cases of cyaniding, carbonitriding and nitriding processes. What is the serious problem encountered in nitriding process? In which process is case hardened thickness maximum? [2009/20m/4c]

19. Define the term proeutectoid cementite. What is the mechanism involved in gas carburizing? What problems exist in nitriding with respect to dimensional stability? What is martempering? What is the function of an energizer in solid carburizing? [2008/30m/4a]

20. What factors influence $M_s$ and $M_f$ temperatures? What is temper brittleness and how might it be avoided? What is the process of spherodizing of steel and what is its purpose? [2008/15m/4b]

21. What is tempering of steel? How is it carried out? Differentiate between Cyaniding and Nitriding. [2007/20m/4d]

22. In a tabulated form briefly outline the procedure, general characteristics and two typical applications of carburizing, cyaniding and boronizing processes. [2005/20m/4a]

23. What is ‘heat treatment’? Differentiate clearly between ‘Annealing’ and ‘Normalising’. [2004/20m/1d]

24. Explain the following: (i) Process annealing (ii) Normalising (iii) Spheroidizing. [2004/15m/4c]

25. Explain the terms ‘Natural aging’ and ‘Artificial aging’. [2004/15m/4d]

26. What is TTT diagram for steel? How is it used in designing heat treatment cycle for steels? [2003/15m/4c]

27. Explain the following: (i) Cyaniding (ii) Nitriding (iii) Flame hardening (iv) Induction hardening. [2002/10m/4c]

28. What are the defects developed by the components of steel of any machine during heat treatment operation? Give the causes for such defects and explain the remedies taken. [2000/20m/1d]

29. What significant information’s are provided by T T T diagrams? Sketch the T T T diagram for high carbon steel with low alloy content. Indicate a cooling line for full hardening. [1999/20m/200w/5b]

2.4] Non-metals

20 questions

1. A glass-epoxy composite consists of full length fibers of E-glass with modulus 72.5 GPa embedded in epoxy matrix with modulus 3.5 GPa. The volume percentage of glass fibers is 35%. Compute: (i) The modulus of elasticity of the composite in longitudinal and transverse directions. (ii) The strain sustained by fibers and matrix, if a stress of 50 MPa is imposed on a cross-sectional area of $250m{m}^2$. [2026/10m/3c]

2. Classify the nanomaterials depending on the number of dimensions in the nano range. Support your answer with the geometry of classified nanomaterials. [2025/10m/2c]

3. Write short notes on the following: (i) Ceramics (ii) Nano-materials. [2023/10m/4c]

4. Compare thermosetting and thermoplastic types of plastics in terms of properties, response to heating and applications. [2022/10m/1d]

5. Classify the nano-materials depending on the number of dimensions in the nano range. What are the two basic approaches for processing of nano-structural materials? [2020/10m/4c]

6. How do the following additives change the properties of polymers: (i) Fillers (ii) Plasticizers (iii) Colourant (iv) Lubricant. [2016/10m/4b]

7. What are polymeric materials? Distinguish between two polymer types. [2014/10m/3b]

8. What are composites? How are they classified? Mention any four applications of composites. [2014/10m/4b]

9. What are composite materials? Enumerate the advantages and limitations of the use of composites as engineering materials. [2013/10m/4c]

10. (i) How are the thermosetting plastic products processed? (ii) Name two polymerization processes. [2012/10m/2c]

11. What are ceramic materials? How do they differ from other materials? How are the ceramics toughened? Give one example. [2011/15m/4d]

12. What is the application of glass fibre reinforced plastic (epoxy)? How do these composites compare with carbon reinforced plastics (epoxy)? [2010/20m/4b]

13. Name four types of thermoplastics and write the characteristics and applications of one type. Write in short about fillers and plasticizers. Define metal-matrix composites, their applications and advantages. [2008/15m/4c]

14. How are plastics broadly classified? What are the advantages and disadvantages of plastic materials? [2007/10m/4c]

15. What are the composite materials? Explain major composite materials, depending upon state of reinforcing phase. [2006/30m/4b]

16. Name any four commonly used reinforcing fibres used in plastic composites. What are their properties and applications? [2005/20m/4b]

17. Differentiate between ceramics, polymers and composites. [2004/15m/4a]

18. What is a ‘hybrid composites’? State the principal applications of hybrid composites. [2004/15m/4b]

19. (i) What are ceramics? How are they classified? (ii) Explain (a) Silicates (b) Vitreous structure (c) Chain structure and (d) Sheet structure as applied to engineering materials. [2000/20m/4b]

20. What are the characteristics of thermoplastic-plastics and how do they differ from thermo-setting plastics? Name the factors that influence the accuracy of moulding of plastic parts. [1998/20m/200w/5b]

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Last updated: 30 October 2026