Using the isothermal transformation diagram for a 1.13 wt% C steel alloy (Figure 10.39), 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 (1690°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 103 s, then quench to room temperature. (b) Rapidly cool to 775°C (1430°F), hold for 500 s, then quench to room temperature. (c) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature. (d) Rapidly cool to 700°C (1290°F), hold at this temperature for 105 s, then quench to room temperature. (e) Rapidly cool to 650°C (1200°F), hold at this temperature for 3 s, rapidly cool to 400°C (750°F), hold for 25 s, then quench to room temperature. (f) Rapidly cool to 350°C (660°F), hold for 300 s, then quench to room temperature. (g) Rapidly cool to 675°C (1250°F), hold for 7 s, then quench to room temperature. (h) 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. Figure 10.39 Isothermal transformation diagram for a 1.13 wt% C iron-carbon alloy: A, austenite; B, bainite; C, proeutectoid cementite; M, martensite; P, pearlite. [Adapted from H. Boyer (Editor), Atlas of Isothermal Transformation and Cooling Transformation Diagrams, 1977. Reproduced by permission of ASM International, Materials Park, OH.] Temperature (°C) 900 800- A+C 700 A+P 600 P 500 A+B T 1600 1400 1200 1000 800 400- A 600 300 50% Mistart 200 400 M(50%) 100 MI90%) 1 10 102 10 Time(s) 105 10% 200 Temperature (F)

Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Animated Figure 10.40), determine the approximate percentages of the microconstituents that form the final microstructure of 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.

Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Animated Figure 10.40), determine the approximate percentages of the microconstituents that form the final microstructure of 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. X Your answer is incorrect. Rapidly cool to 250°C (480°F), hold for 103 s, then quench to room temperature. martensite % ferrite % bainite spheroidite % austenite %

Question 4: Using the following TTT diagram for an iron-carbon alloy of eutectoid composition, specify the nature of the final microstructure (in terms of microconstituents 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°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure.

Question 4: Using the following TTT diagram for an iron-carbon alloy of eutectoid composition, specify the nature of the final microstructure (in terms of microconstituents 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°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. (1) Cool rapidly to 700°C (1290°F), hold for 104 s, then quench to room temperature (ii) Reheat the specimen in part (1) to 700°C (1290°F) for 20 h. (iii) Cool rapidly to 400°C (750°F), hold for 20 s, then quench to room temperature (iv) Cool rapidly to 400°C (750°F), hold for 200 s, then quench to room temperature. (v) Rapidly cool to 575°C (1065°F), hold for 20 s, rapidly cool to 350°C (660°F), hold for 100 s, then quench to room temperature. (vi) Rapidly cool to 250°C (480°F), hold for 100 s, then…

800 A Eutectoid temperature H 1400 700 A H 1200 600 1000 500 B 800 400 A 300 600 M(start) 200 M + A 50% 400 M(50%) M(90%) 100 200 10-1 1 10 102 103 104 105 Time (s) Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition, specify the final microstructure and approximate amount of each. Assume a small specimen has been held long enough to have achieved a complete and homogeneous austenitic structure prior to treatment. Sample (1): Quickly cool specimen from 800°C to 575°C, hold for 10 s, then quench to room temperature. Sample (2): Quickly cool specimen from 800°C to 500°C, hold for 100 s, then quench to room temperature. O after treatment, sample 1 is 50% pearlite, 50% austenite O after treatment, sample 2 is bauxite O after treatment, sample 1 is 25% pearlite O after treatment, sample 2 is bainite O after treatment, sample 2 is austenite O None of the answers is correct. O after treatment, sample 2 is coarse pearlite O after treatment, sample 1 is…

1. Using the TTT diagram for Eutectoid Steel, specify the constituents and their approximate percentages of a small specimen subjected to the following time-temperature treatments. All begin with a completely Austenized specimen: - Rapidly cool to 650°C, hold for 100 seconds, then quench to room temperature. Rapidly cool to 500°C, hold for 100 seconds, then quench to room temperature. - Rapidly cool to 350°C, hold for 100 seconds, then quench to room temperature. - Rapidly cool to 100°C, hold for 100 seconds, then quench to room temperature. - Rapidly cool to 500°C, hold for 4 seconds, quench to 300°C, hold for 200 seconds, then quench to room temperature.

An uncold-worked brass specimen of average grain size 0.006 mm has a yield strength of 178 MPa. Estimate the yield strength of this alloy (in MPa) after it has been heated to 600°C for 1000 s, if it is known that the value of ky is 11 MPa-mm1/2. The Animated Figure 7.25 may be helpful. Attached is the question and the figure referenced.

Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition, sketch (mark the microconstituents, eg. a-Fe, Fe,C) and specify the name of the final microstructure (e.g. austenite, pearlite, bainite etc.) of a small specimen that has been subjected to the following time-temperature treatment. In each case assume that the specimen begins at 760 Cand that is has been held at this temperature long enough to have achieved a complete and homogeneous austenite structure. 800 -Eutectoid temperature 1400 700 1200 600 1000 500 800 400 300 600 Mistart) 200 50% 400 ME50%) M90%) 100 200 10 10 10 10 10 10 Time ( eoha ileySons, lnc. Al righta reserved (a) Cool rapidly to 350 S, hold for 10' s, then quench to room temperature (b) Cool rapidly to 665 S, hold for 10's, then quench to room temperature (c) Cool rapidly to 150gin 5 seconds, then cool to room temperature (d) Cool rapidly to 300gin 1 second, then cool to room temperature in 10s (3J anjedueI Temperature F)

A Cu-30% Zn brass plate, originally 1.20 inches thick, is desired to have a yield strength greater than 50,000 psi and a percent elongation of at least 15%. The final geometry of the plate will be obtained by means of cold work. What range of final thicknesses is possible to obtain under the given conditions? The effect of percent cold work on Cu-3096 Zn brass properties is shown below. 100 80 Resistencia a la tensión (ksi) 60 Límite elástico (ksi) 20 Porcentaje de elongación 20 40 60 80 Porcentaje de trabajo en frío Propiedad