Intro to Austenite 上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY In Fe-C system:austenite solid solution of C in fcc Fe All octahedral interstices occupied? →50at%C,or,20wt%C →Maximum2.11wt%C →Therefore,No！ →The maximum is10at%C 0.364 0.362 wu/ Fe 0.360 Because: 1A0 Radius of C is 0.77A 0.358 >Radius of octahedral site is 0.52A >Lattice distortion>100%occupied 0.356 impossible Lattice parameter 0 0.5 1.0 1.5 2.0 increase C Concentration / K.Chen 9K. Chen Intro to Austenite 9 In Fe-C system: austenite solid solution of C in fcc Fe All octahedral interstices occupied?  50 at% C, or, 20 wt% C  Maximum 2.11 wt% C  Therefore, NO!  The maximum is 10 at% C Because:  Radius of C is 0.77Å  Radius of octahedral site is 0.52Å  Lattice distortion  100% occupied impossible  Lattice parameter increase C Concentration /% Austenite Lattice Parameter /nm