Question

8) Which of the following statements is ? a) Steel with high carbon content is usually highly ductile b) Primary ferrite is harder than pearlite c) Fine pearlite has higher strength than coarse pearlite d) Steel with 0.3 wt% carbon quenched from 1000 C to room temperature commis 37.2% Martensite and 62.8% Ferrite. e) None of the above 9. Refer to the Po- Sn phase diagram. In a crucible 200 g of an alloy containing 80 g of Sa and 120 g of Pb are kept at a temperature slightly above 183 C a) There are about 100 g of B and 100 g of liquid b) There are about 100 g of a and 100 g of liquid. c) The liquidus temperature for this alloy is 183 C d) There are 19 g of a, 97.5 g of B, and the rest is liquid. e) There are about 100 g of eutectic microconstituent. 10) Which of the following statements best describes the expected properties or applicability of a material A that has an appreciably higher coefficient of thermal expansion than that of B? material a) A has stronger interatomic bonding than B does. b) A has weaker interatomic bonding than B does. c) A has higher melting temperature than B does. d) A will be more desirable than B in applications where dimensional stability is important. e) None of the above. 11) A bar made ofan aluminum alloy (E = 1.0 107 psi, yield strength 35,000 psi) is firmly attached, when at room temperature, to two opposite walls 10 m apart. While all else stays the same, the bar is then cooled so its temperature decreases by 10 °C, still remaining firmly attached at the ends to the walls. The thermal expansion coefficient of the aluminum alloy is 2.4 10-3 C. Estimate the value of the tensile stress acting on the bar as a result of the cooling a) 10,000,000 psi b) 0 psi c) 14,400 psi d) 2,400 psi e) 35,000 psi

Answer 1

8)C

9) Cannot answer since phase diagram not given

10)B (Since A has higher coeffecient of linear expansion which indicates it expands more due to vibration of molecules. Thus If vibration is more means the force of attraction between molecule is less)

11)D
0 AE