Temperature, C 1000 Ystable 800 -790C 727C 600 400 + +carbide a+carbide Yunstable tf Ms + 200 M 0 0.1 1.0 M 10 912C a+r a+carbide 100 1000 0.45% C Time, sec (log scale) (a) (b) Fig. 11-4.6 Isothermal-transformation diagram for SAE 1045 steel. The stable phases of the phase diagram (right) are not achieved immediately. However, in this steel, the austenite decomposition reaction is faster than in a eutectoid steel (Fig. 11-4.1).