7) The term allotropy is normally reserved for this behavior in pure elements /compounds, while the term polymorphism is used for elements/compounds. 8) As the extent of undercooling decreases/ increases, the thermodynamic driving force for the formation of a solid phase from the liquid is decreased/ increased. Q3 (5 pts): Multiple Choice Answer 10 of 12 (0.5 pts each) 1) As the temperature of a metal increases, the vacancy concentration a) decreases b) increases c) remains the same 2) Which of the following statements is NOT true a) The [100], [010] & [001] are equivalent in the cubic system b) The [100] & [001] are equivalent in the cubic system c) The [100], [010] & [001] are equivalent in the tetragonal system d) The [100] & [010] are equivalent in the tetragonal system 3) The greater a materials Young's modulus the a) stiffer b) weaker 4) The pearlite microstructure is formed a) in hypereutectoid steels c) in eutectoid steels d) all of the above 5) Within the elastic limit c) more ductile a) Strain is produced by bond breaking and reforming b) Stress is proportional to strain c) Complete recovery of strain is not possible d) Strain is produced by bond stretching e) b and d, are correct f) a and b, are correct 7) Most metals are, 73 the material. a) single crystals b) in hypoeutectoid steels e) none of the above 6) Boron can diffuse in silicon can by either a vacancy or interstitial mechanism. Which statement is probably true? a) Dint Dvac b) Dint= Dvac c)Dint Dvac d) none Diffusion faster for materials with: a. closed-packed structure. c. higher melting T. d) tougher polycrystalline c)mixtures of amorphous regions interspersed with single crystals d) amorphous b. higher density. d. lower melting T.