Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure 10.40), determine the final microstructure (in terms of just the microconstituents present) AND approximate percentages of the microconstituents that form in a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 845°C (1550°F), and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. (a) Rapidly cool to 250°C (480°F), hold for 10^3 s, then quench to room temperature. (b) Rapidly cool to 700°C (1290°F), hold for 30 s, then quench to room temperature. (c) Rapidly cool to 700°C (1290°F), hold at this temperature for 10^5 s, then quench to room temperature.  (d) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature.

8)

A cylindrical metal specimen having an original diameter of 10.63 mm and gauge length of 50.1 mm is pulled in tension until fracture occurs. The diameter at the point of fracture is 7.60 mm, and the fractured gauge length is 74.5 mm. Calculate the ductility in terms of (a) percent reduction in area (percent RA), and (b) percent elongation (percent EL). (a) i percent RA (b) i percent EL

14) Inc a) Copper and its alloys do not fail due to cycling loading if the applied stress amplitude is below a certain level. b) Alloys with HCP crystal structure do not fail due to cycling loading if the applied stress amplitude is below a certain level. c) If there exist many slip systems such metals and alloys do not fail due to cycling loading if the applied stress amplitude is below a certain level. d) The practical rule that says there exist a fatigue limit for iron based alloys is not strictly true. 15) Indicate the incorrect expression: a) Better surface finish would help increase fatigue life. b) All kinds of inhomogenity would be detrimental in number of cycles that material can terms of the endure regardless of the stress level. c) Corrosion on a material that has excellent surface finish would not affect fatigue behavior of that part. d) Sand blasting as a source of compressive stresses would be useful under fatigue conditions