ME-303 Materials Technology - Jun 2023 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWhat do you understand by the term crystal lattice and how many types of this are found in metals?
   How to answer

   • Define crystal lattice and unit cell.
   • Mention Bravais lattices (14 space lattices).
   • Describe common crystal structures in metals: BCC, FCC, and HCP with examples.
2. 7 Marks
   bWhat are the factors affecting fatigue strength of material?
   How to answer

   • Define fatigue strength and endurance limit.
   • List key factors: stress concentration (notches, geometry), surface finish, heat treatment/residual stress.
   • Discuss environmental factors: temperature and corrosion.
   • Explain the effect of grain size and microstructure.
3. 7 Marks
   aExplain impact properties of materials as applied to design.
   How to answer

   • Define impact strength/toughness and resistance to shock loading.
   • Explain testing methods (Charpy/Izod test).
   • Discuss factors in design: notch sensitivity, stress concentration, temperature (ductile-to-brittle transition temperature - DBTT).
   • Application considerations in structural and automotive design.
4. 7 Marks
   bExplain Dispersion bonds and dipole bonds.
   How to answer

   • Explain secondary bonding (van der Waals bonds).
   • Define dipole bonds: interactions between permanent dipoles.
   • Define dispersion bonds (London dispersion forces): interactions resulting from temporary/induced fluctuating dipoles.
   • Compare bond strengths and give examples for each.
5. 7 Marks
   aDraw the phase diagram for a binary system showing solubility in liquid and solid state.
   How to answer

   • Draw an isomorphous binary phase diagram (e.g., Cu-Ni system).
   • Label axes: Temperature vs Composition (wt%).
   • Identify Liquidus line, Solidus line, and phases (Liquid, Liquid + Solid, Solid $\alpha$).
   • Briefly explain complete solubility in both liquid and solid states according to Hume-Rothery rules.
6. 7 Marks
   bWhat do you understand by a solid solution? Explain with neat sketches the substitutional solid solution and interstitial solid solution given two examples of each in the alloy system.
   How to answer

   • Define solid solution.
   • Explain Substitutional Solid Solution with neat sketch and 2 examples (e.g., Cu-Ni, Cu-Zn brass).
   • Explain Interstitial Solid Solution with neat sketch and 2 examples (e.g., C in $\alpha$-Fe/ferrite, C in $\gamma$-Fe/austenite).
   • Mention size factor criterion (Hume-Rothery rules).
7. 14 Marks
   Explain the working of TTT diagram and what information is supplied by them.
   How to answer

   • Define TTT diagram (Time-Temperature-Transformation or C-curve).
   • Draw and label a typical TTT diagram for eutectoid steel (0.77% C).
   • Explain its working: Austenitizing temperature, rapid quenching, isothermal holding, start and finish curves.
   • List the information supplied: transformation phases (pearlite, bainite, martensite), nose of the curve, critical cooling rate, incubation periods, and percent transformation.
8. 7 Marks
   aExplain the process of austempering and martempering.
   How to answer

   • Explain Austempering: Austenitizing, quenching to temperature above Ms, isothermal holding until complete transformation to bainite, and air cooling.
   • Explain Martempering (Marquenching): Austenitizing, quenching to temperature just above Ms, holding to equalize temperature throughout, and cooling through martensite range to form tempered martensite with minimal distortion.
   • Draw cooling curves superimposed on TTT diagram for both processes.
   • State advantages and typical applications of each.
9. 7 Marks
   bWhat are common defects observed during heat treatment. Describe a few precautions for their prevention.
   How to answer

   • Enumerate common defects: distortion/warping, quench cracking, oxidation, decarburization, overheating, burning, and soft spots.
   • Explain causes for each defect (e.g., uneven heating/cooling, improper quenchant, furnace atmosphere).
   • Describe preventive measures and precautions: proper support in furnace, uniform heating/cooling, protective atmosphere, correct quenching medium and agitation, preheating.
10. 7 Marks
    aExplain the theory of tempering.
    How to answer

    • Define tempering: reheating quenched martensitic steel below lower critical temperature ($A_1$) followed by controlled cooling.
    • Explain the objective: relieve internal stresses, improve ductility/toughness while reducing hardness/brittleness.
    • Describe the stages of tempering: Stage 1 (precipitation of transition carbide/$\epsilon$-carbide), Stage 2 (decomposition of retained austenite), Stage 3 (formation of ferrite and cementite / spheroidization).
    • Discuss mechanical property changes as a function of tempering temperature.
11. 7 Marks
    bExplain the Brinell hardness testing of mild steel specimen.
    How to answer

    • State the principle of Brinell Hardness testing.
    • Specify test parameters for mild steel: standard indenter (10 mm hardened steel or tungsten carbide ball), load $P = 3000\text{ kgf}$ ($P/D^2 = 30$), dwell time (10-15 seconds).
    • State the formula: $\text{BHN} = \frac{2P}{\pi D (D - \sqrt{D^2 - d^2})}$.
    • Describe procedure: specimen preparation, load application, measurement of indentation diameter ($d$) using microscope, and BHN calculation.
12. 7 Marks
    aWhat are the composition, structure and characteristics of Copper Tin Bronze.
    How to answer

    • State chemical composition of phosphor/tin bronzes (Cu base with typically 5-15% Sn, up to 0.4% P).
    • Describe microstructure: single-phase $\alpha$ solid solution or $\alpha + \delta$ eutectoid depending on Sn content.
    • List key characteristics: high tensile strength, excellent corrosion resistance (especially seawater), good anti-friction properties, wear resistance.
    • State typical applications: bearings, bushings, marine fittings, bells, gears.
13. 7 Marks
    bWhat is Monel Metal? Write composition and uses.
    How to answer

    • Define Monel Metal: a group of nickel alloys primarily composed of nickel and copper.
    • Give typical composition: ~65-67% Ni, ~28-30% Cu, plus small amounts of Fe, Mn, C, Si.
    • State main properties: high strength, resistance to corrosion by acids, seawater, and alkalis.
    • List common uses: marine engineering valves/pumps, chemical processing equipment, aerospace, musical instrument valves.
14. 7 Marks
    aDescribe optical and spectrophotometric analysis.
    How to answer

    • Define optical analysis: use of optical microscopy/emission spectroscopy for microstructure and elemental inspection.
    • Define spectrophotometric analysis: quantitative measurement of reflection or transmission properties of a material as a function of wavelength.
    • State governing principle: Beer-Lambert Law ($A = \varepsilon c l$).
    • Explain instrumentation/steps: light source, monochromator, sample holder, detector.
    • Describe applications in materials technology (composition analysis, impurity detection).
15. 7 Marks
    bWhat is spot test? How it is used for determination of metal?
    How to answer

    • Define spot test: a rapid qualitative chemical micro-test technique involving drops of chemical reagents on metal surfaces or filter paper.
    • Explain the principle: color reaction between the specific reagent and the metal ions.
    • Describe procedure/steps: surface cleaning, applying reagent drop, observing color change.
    • Give specific examples: testing for Nickel (dimethylglyoxime giving red precipitate), testing for copper, iron.
    • Explain its practical utility in non-destructive alloy sorting and quality control.