Formation Mechanism 上海充通大粤 SHANGHAI JIAO TONG UNIVERSITY 2.Austenite Nucleus Growth Fe,C a/cem ycem cem/y Interlamellar spacing So! C Concentration Concentration gradient in austenite (CCdiffusion of C inside of austenite lower the concentration gradient to(Cem-C Leading to dissolution of cementite at y/Fe C to increase C to Cem and ferrite to austenite transformation to lower Cto C Spontaneous growth of austenite K.Chen 16K. Chen Formation Mechanism 16 2. Austenite Nucleus Growth Cα/γ Cα/cem Cγ/α Cγ/cem Ccem/γ Concentration gradient in austenite (Cγ/cem - Cγ/α)  diffusion of C inside of austenite  lower the concentration gradient to (C′ γ/cem - C′ γ/α) Leading to dissolution of cementite at γ/Fe3C to increase C′ γ/cem to Cγ/cem and ferrite to austenite transformation to lower C′ γ/α to Cγ/α  Spontaneous growth of austenite Temperature C Concentration C Concentration Interlamellar spacing S0