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5. Using the TTT diagram for a eutectoid steel, determine the structure that results from the following treatments. In each case, assume that you start with a homogeneous austenitic structure. CLEARLY indicate the structure after each step in the treatment. i) Rapidly cool to 700°C hold for 2 s Rapidly cool to 525°C Hold for3 s Rapidly cool to 300°C Hold for 10 s quench to room temperature ii) Rapidly cool to 650°C hold for 1s Rapidly cool to 600°C hold for 4 s Rapidly cool to 350°C Hold for 200 s quench to room temperature

3. Using the isothermal transformation diagram for a 1.13 wt% C steel alloy (Figure 11.49 in your book), determine the final microstructure (in terms of just the microconstituents present) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 920°C 01690°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 775 C (1430 F), hold for 500 s, then quench to room temperature. (b) Rapidly cool to 700eC(1290°F), hold at this temperature for 105 s, then quench to room temperature. (c) Rapidly cool to 350°C (660 F), hold for 300 s, then quench to room temperature. (d) Rapidly cool to 600°C (1110 F), hold at this temperature for 7 s, rapidly cool to 450°C (840 F, hold at this temperature for 4 s, then quench to room temperature.

Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition, specify the nature of the final microstructure (in terms of micro constituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 760 degree C (1400 degree F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Cool rapidly to 700 degree C (1290 degree F), hold for 10^4 s, then quench to room temperature. Reheat the specimen in part (a) to 700 degree C (1290 degree F) for 20 h. Rapidly cool to 600 degree C (1110 degree F), hold for 4 s, rapidly cool to 450 degree C (840 degree F), hold for 10 s, then quench to room temperature. Cool rapidly to 400 degree C (750 degree F), hold for 2 s, then quench to room temperature.

Using the T-T-T diagram for an iron-carbon alloy of eutectoid composition shown in figure below, specify the nature of the final micro structure (in terms of micro- constituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 760 degree C and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Also use fine or coarse for pearlite wherever applicable. (a) Cool rapidly to 375 degree C, hold for 2000 s, then quench to room temperature. (b) Rapidly cool to 580 degree C, hold for hold till reaching the blue dashed line, then quench to room temperature. (c) Rapidly cool to 620 degree C. hold till reaching the blue dashed line, rapidly cool to 450 degree C. hold for 10 s (use the time reset just as done in example in the class), then quench to room temperature. (d) Cool rapidly to 675 degree C, hold for 10^4 s, then quench to room temperature. (e) Rapidly cool to 600 degree C. hold for 15 s, rapidly cool to 360 degree C. hold for 100 s, quench to room temperature. (f) Rapidly cool to 350 degree C. hold for 150 s, then quench to room temperature.

r(t) = (cos t + t sin t) i + (sin t - t cos t) j + 4k (a) Find T(pi/2) (b) Find N (pi/2) (c) Find B(pi/2)