Temperature (C) 1600 1538C 1493C 5 10 1400 1394C Y+L 1200 y, Austenite 2.14 1000 912C 800 +7 + 600 0.76 0.022 a, Ferrite 400 0 (Fe) 2 Composition (at% C) 15 20 20 L 1147C 4.30 a + Fe3C 3 Composition (wt% C) y + Fe3C 727C 25 2500 2000 1500 Cementite (Fe3C) 1000 4 5 6 6.70 Temperature (F) Temperature Ael Y+P Y+UB very FP+UB Y+LB Metastable y Ms y+Fe3C Fe3C+CP Fe3C+P Fe3C+FP UB Hardness y=austenite CP=coarse pearlite P=pearlite FP=fine pearlite UB=upper Bainite LB=lower Bainite M=martensite Ms-Martensite start temperature M50 temperature for 50% martensite formation Metastable y + M M50 Log time LB 23