6.1 components and phases in Fe-C alloy The Fe-Fe3C diagram contains the following solid phases:a ferrite,austenite (y),cementite (Fe3C) andδferrite. a ferrite(F):an interstitial solid solution of carbon in a-Fe.Carbon is slightly soluble in a ferrite,the maximum solid solubility is 0.0218%at 727C Austenite(y/A):an interstitial solid solution of carbon in y-Fe.Austenite has a much higher solid solubility for carbon than a ferrite,the maximum solid solubility is 2.11%at 1148C Cementite (Fe3C):the intermetallic compound, with a composition of 6.69%C and 93.1%Fe. Hard and brittle
The Fe-Fe3C diagram contains the following solid phases: α ferrite, austenite (γ), cementite (Fe3C) and δ ferrite. α ferrite(F): an interstitial solid solution of carbon in α-Fe. Carbon is slightly soluble in α ferrite, the maximum solid solubility is 0.0218% at 727℃ Austenite(γ/A): an interstitial solid solution of carbon in γ –Fe. Austenite has a much higher solid solubility for carbon than α ferrite, the maximum solid solubility is 2.11% at 1148℃ Cementite (Fe3C): the intermetallic compound, with a composition of 6.69% C and 93.1% Fe. Hard and brittle. 6.1 components and phases in Fe-C alloy
Austenite
Austenite
Cementite
Cementite
6.2 Fe-Fe3C phase diagram 6.2.1 analysis of Fe-Fe3C phase diagram T Fe Fe3C
Fe T° Fe3C 6.2 Fe - Fe3C phase diagram 6.2.1 analysis of Fe - Fe3C phase diagram
Fe-Fe;C phase diagram T Isomorphous Eutectic L D L+A 1148℃ C L+Fe3C A (A+F3C) F G Eutectoidic A+ a Ld+Fe3CI A+F Fe:CI A+Ld+Fe3CI 727℃ F P (F+iFe3C K 2 P+Ld'+FesCn Ld' Ld'+Fe3CI P+F P+Fe:Cu (P+Fe3C) 0.0218%C 0.77%C 2.11%C 4.3%C 6.69%C Fe Fe3C
Fe - Fe3C phase diagram A C D E F G S P Q 1148℃ 727℃ L A L+A L+ Fe3CⅠ 0.0218%C 2.11%C 4.3%C 6.69%C Fe Fe3C T° ( A+Fe3C ) Ld Ld+Fe3CⅠ A+Ld+Fe3CⅡ F A+F A+ Fe3CⅡ ( F+ Fe3C ) P P+F 0.77%C P+Fe3CⅡ P+Ld’+Fe3CⅡ Ld’ Ld’+Fe3CⅠ K Eutectic Eutectoidic Isomorphous ( P+Fe3C )