Question

Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Figure 10.22), 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 (a) Cool rapidly to 350°C (660°F), hold for 103 s, then quench to room temperature (b) Rapidly cool to 625 C (1160°F), hold for 10 s, then quench to room temperature (c) Rapidly cool to 600°C (1110°F), hold for 4 s, rapidly cool to 450°C (840°F), hold for 10 s, then quench to room temperature (d) Reheat the specimen in part (c) to 700°C (1290 F) for 20 h (e) Rapidly cool to 300°C (570°F), hold for 20 s, then quench to room temperature in water. Reheat to 425°C (800°F) for 103 s and slowly cool to room temperature (f) Cool rapidly to 665 C (1230°F), hold for 103 s, then quench to room temperature (g) 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 (h) Rapidly cool to 350°C (660°F), hold for 150 s, then quench to room temperature Figure 10.22 The complete isothermal transformation diagram for an iron-carbon alloy of eutectoid composition: A, austenite; B, bainite, M, martensite, P, pearlite

Detailed Subject: Materials Science and Engineering

Please make a full explanation and plot in the isothermal diagrams using the graph above.

Answer 1