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Unformatted text preview: Mat E 272 Extra Practice exam 1 1) What is the linear density in the <111> direction in an ideal FCC structure? Z
2) Name the direction shown to the right 1/2 Y
X Z 3) Name the plane shown to the right 1/2 Y X 4) What is the atomic packing factor in a simple cubic structure? Mg Pb For questions 5‐8, use the phase diagram above 5) In a 50wt% Pb alloy, what phases are present at 500°C? 6) In a 50wt% Pb alloy, what is the composition of α at 350°C? 7) In a 50wt% Pb alloy, what fraction of the total phases present are Mg2Pb and β, respectively? 8) If a 30wt% Pb alloy is cooled from 700°C to 200°C, what fraction of eutectic structure would be formed? 9) In a 20wt% Pb alloy, what is the composition of α present at 400°C? 10) Tungsten has a BCC structure and an atomic radius of 1.371Å. What is its lattice parameter? 11) You have a metal cylinder 2” tall and 1” in diameter, with a modulus of elasticity of 20 x 106 PSI, and a yield strength of 6000 PSI. If you press on the ends of the cylinder with 2000 lbs. force, what is the change in height of the cylinder? 12) What fraction of lattice sites would be vacant for a metal at 27°C with activation energy (Ev) =0.15eV? σ 1
13) The stress vs. strain diagram to the right shows 2 curves for a metal, glass, and a plastic. State which 3
curve corresponds to which material. ε 14) You have a pure copper block (C0=0% Zn). You want to create a layer of brass by diffusing zinc into the copper. The diffusion coefficient for zinc in copper at 600°C is 2.0 X 10‐13 m2/sec. If you place the block into a 60% Zn environment (Cs=60%) at 600°C for 5555 seconds, what is the composition at x = 0.1mm? (assume that the block is a semi‐infinite solid) ...
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- Fall '06