HW4 Problems_2.pdf - 1(a Briefly describe the phenomena of...

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1 (a) Briefly describe the phenomena of superheating and supercooling. (b) Why do these phenomena occur? 2 Make a copy of the isothermal transformation diagram for a 0.45 wt% C iron-carbon alloy (Figure 10.40), and then sketch and label on this diagram the time-temperature paths to produce the following microstructures: (a) 42% proeutectoid ferrite and 58% coarse pearlite (b) 50% fine pearlite and 50% bainite (c) 100% martensite (d) 50% martensite and 50% austenite 3 Briefly explain why the hardness of tempered martensite diminishes with tempering time (at constant temperature) and with increasing temperature (at constant tempering time).
4 Show that the minimum cation-anion radius ratio for a coordination number of 6 is 0.414. [Hint: Use the NaCl crystal structure (Figure 12.2), and assume that anions and cations are just touching along cube edges and across face diagonals.] 5 Iron sulfide (FeS) may form a crystal structure that consists of an HCP arrangement of S 2- ions.

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