4.cementite(Fe3C)The composition axis extends only to 6.69wt%. At thisconcentration, the intermediate compound iron carbide,orcementite, which is vertical line on the phase diagramWhenthe solubility limit of carbon in a ferrite isexceeded below727C,cementite(Fe3C)formsBeside this,Fe3Cwill also coexist withthephasebetween 727and1147°CMechanically,cementiteis veryhard and brittle,so thestrength of some steels is greatly enhanced by itspresence
4. cementite(Fe3C) When the solubility limit of carbon in a ferrite is exceeded below 727 C , cementite(Fe3C) forms. The composition axis extends only to 6.69wt%. At this concentration, the intermediate compound iron carbide, or cementite, which is vertical line on the phase diagram. Beside this, Fe3C will also coexist with the g phase between 727 and 1147 C . Mechanically, cementite is very hard and brittle, so the strength of some steels is greatly enhanced by its presence
LThe eutectic reactionThe eutectic reaction exists for the iron-iron carbidesystem,at4.3wt%Cand1147Ci1147°CYe + FeCFe.cProducts:Ld(Ledabunite).themixtureofandFe3C（莱氏体）莱氏体
I. The eutectic reaction The eutectic reaction exists for the iron-iron carbide system, at 4.3wt%C and 1147 C gE Fe3C Products: Ld(Ledabunite):the mixture of g and Fe3C(莱氏体） 莱氏体 Lc gE + Fe3C 1147C