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BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI

STRUCTURE & PROPERTIES OF MATERIALS (ES C242)

(II Semester 2009-10)Date: 03-05-2010Max Marks: 100

II-AComprehensive Examination (C.B.)Max Time: 150 minWeightage 33.33 %

==============================================================1: Metal G has an HCP crystal structure with c

a= 1.623, density of 8.9 g/cm3 and atomic weight of 58.9 g/m

Determine:a) Volume of the unit cell in m3. [5] b) Values ofc and a, in nm. [10]2: (a) Convert [101], [313] directions into 4-index Miller-Bravais scheme for hexagonal unit cells. [4] (b) Sketwithin a cubic unit cell, the directions [212], [331] and [312]. Use three different figures for each direction, aspecify the origin clearly. [6]3: (a) Write down the point coordinates for tetrahedral and octahedral interstitial sites in a FCC unit cell?(b) Calculate the radius of largest atom which can occupy the octahedral void of FCC unit cell where the radof the atoms of the unit cell is R. [4] (c) Evaluate the radius of atom that just fits into interstitial site of BCunit cell? [5]4: When iron is subjected to an atmosphere of nitrogen gas, the concentration of nitrogen in the iron, CNwt %), is a function of hydrogen pressure, pN2 (in MPa), and absolute temperature (T) according to

CN = 4.90 103pN2 exp37.6 kJ/mol

RT

Furthermore, the values ofD0 and Qd for this diffusion system are 3.0107 m2/s and 76,150 J/mol, respectiveConsider a thin iron membrane 1.5 mm thick that is at 300 0C. Compute the diffusion flux through this membraif the nitrogen pressure on one side of the membrane is 0.10 MPa and on the other side 6.0 MPa. (R = 8.3J/mol) [10]

II-B1: For 3 kg copper-silver alloy of composition 20 wt% Cu-80 wt% Ag and at temperature just below eutec

isotherm, determine the following:(a) The primary (proeutetctic) phase. [1] (b) The mass (in kg) of and phases. [2] (c) The mass of primaphase and eutectic composition. [2] (d) The volume fraction of primary phase, eutectic and eutectic pha[1+1+2+2+2] The densities of copper and silver at eutectic temperature are 8.90 g/cm3 and 10.43 g/cmrespectively.

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2: A 1.5 kg of specimen of 98 wt% Cu-2 wt% Ag alloy is heated to 1000 0C. The alloy is to be melted to the extethat 1.05 kg of the specimen is liquid and remainder being -phase. This may be accomplished by changing composition while holding the temperature constant. How much silver must be added to the 1.5 kg specimen1000 0C to achieve this state? [6]3: A car of mass 25 gram is supposed to move a distance of at least 3 m with an acceleration of 100 mm/s2. Trequired energy for this purpose is to be recovered by deforming an alloy upto its yield point. The moduluselasticity and yield strength of the alloy are 180 GPa and 830 MPa, respectively. Assuming that the entire enerrecovered in this way is used in moving the car, how much the minimum volume of the alloy is needed? [6]

4: What are the Miller indices of the slip di-rection (i) on the (111) plane in an FCC unitcell and (ii) on the (011) plane in a BCC unitcell? (ANSWER BOTH (i) and (ii) SIMUL-TANEOUSLY) [5]5: Using the continuous cooling transforma-tion diagram for an alloy steel (type 4340)shown in figure 2,(a) Determine the final microstructure {interms of (i) phases and (ii) micro constituentspresent} of a specimen that is first trans-formed to Austenite and then cooled toroom temperature at a rate of 0.05 0C/s.(ANSWER BOTH (i) and (ii) SIMULTANE-OUSLY) [7](b) What is the minimum cooling rate re-quired to form the complete Martensite? [1]

6: The Fe Fe3C eutectoid reaction [(0.76wt% C) (0.022 wt% C) + Fe3C(6.70 wt%C)] is fundamental to the development of mi-crostructure in steel alloys. Using the isother-mal transformation diagram for a 1.13 wt% Csteel alloy, as shown in figure 3,(a) Determine the final microstructure {interms of (i) phases and (ii) micro constituentspresent} of a small specimen that has beenrapidly cooled from 900 0C to 650 0C, heldat this temperature for three seconds, thenrapidly cooled to 400 0C and held for 30 sec-onds and then quenched to room temperature.(ANSWER BOTH (i) and (ii) SIMULTANE-OUSLY) [7]

(b) Austenite at 900 0C is rapidly cooled to300 0C, how long it should be maintained at300 0C to transform it to 50% Bainite? [2](c) How Martensite is converted into Tem-pered Martensite? What are the phasespresent in Tempered Martensite? [3]

=====================BEST OF LUCK=========================

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IAComprehensive Examination (C.Max Time: 30 minWeightage 6.67 %

==============================================================Important1. Write the correct and precise answer in the box given after each question.2. Each question contains 4 marks.3. No negative marking is for wrong answer.4. This part you have to complete in 30 minutes and after submission only you can collect the part II.==============================================================

NAME ID SECTION INSTRUCTOR MARKS

1: The diffraction pattern of a sample of BCC metal was recorded using X-rays of wavelength 0.1541 nm. Fidiffraction peak was found to be at 2 = 44.7040. Assuming the first order diffraction, what should be the vaof the lattice parameter, a, (in nm) of the sample?ANSWER

2: The radius of an atom in a BCC crystal is 0.124 nm. If unit cells of this crystal are lined up side by side, homany unit cells will be in 1 cm of length?ANSWER

3: If there are 25 grains per square inch on a photomicrograph of a metal at 75, what is the ASTM grain snumber of the metal?ANSWER

4: Find out the linear density of Ca2+ ions (in number per nm) along the [110] direction of CaO. (Ionic radiiCa2+ and O2 are 0.106 nm and 0.142 nm, respectively.)ANSWER

5: For a 79.65 wt% Fe-0.35 wt% C alloy at a temperature just below the eutectoid temperature, determine tfraction of (i) total ferrite and (ii) the eutectoid phase. The eutectoid reaction is [(0.76 wt% C) (0.022 wC) + Fe3C(6.70 wt% C)]ANSWER

(i) (ii)

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IBComprehensive Examination (C.Max Time: 30 minWeightage 6.67 %

==============================================================Important1. Write the correct and precise answer in the box given after each question.2. Each question contains 4 marks.3. No negative marking is for wrong answer.4. This part you have to complete in 30 minutes and after submission only you can collect the part II.==============================================================

NAME ID SECTION INSTRUCTOR MARKS

1: The diffraction pattern of a sample of BCC metal was recorded using X-rays of wavelength 0.1762 nm. Fidiffraction peak was found to be at 2 = 300. Assuming the first order diffraction, what should be the valuethe lattice parameter, a, (in nm) of the sample?ANSWER

2: The radius of an atom in a BCC crystal is 0.287 nm. If unit cells of this crystal are lined up side by side, homany unit cells will be in 1 inch of length?ANSWER

3: If there are 55 grains per square inch on a photomicrograph of a metal at 80, what is the ASTM grain snumber of the metal?ANSWER

4: Find out the linear density of Na+ and ions (in number per nm) along the [110] direction of NaCl. (Ionic raof Na+ and Cl are 0.102 nm and 0.181 nm, respectively.)ANSWER

5: For a 79.65 wt% Fe-0.35 wt% C alloy at a temperature just below the eutectoid temperature, determine tfraction of (i) proeutectoid ferrite and (ii) the eutectoid phase. The eutectoid reaction is [(0.76 wt% C) (0.0wt% C) + Fe3C(6.70 wt% C)]ANSWER

(i) (ii)

es_c242_563_c_2009_2

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