Using the isothermal transformation diagram for a 113 wt C s

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 degree C (1690 degree F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. Rapidly cool to 775 degree C (1430 degree F), hold for 500 s, then quench to room temperature. Rapidly cool to 700 degree C (1290 degree F), hold at this temperature for 10^5 s, then quench to room temperature. Rapidly cool to 350 degree C (660 degree F), hold for 300 s, then quench to room temperature. Rapidly cool to 600 degree C (1110 degree F), hold at this temperature for 7 s, rapidly cool to 450 degree C (840 degree F), hold at this temperature for 4 s, then quench to room temperature.

Solution

T-T-T diagram not given for this steel. Using typical diagram the results are:

a) A+C

b) P

c) A+P

d) A+P or P===> P

A = austenute

C= cementite

P =pearlite