material A steel of Co 076 wtC is slowly cooled from 875 de

A steel of Co = 0.76 wt%C is slowly cooled from 875 degree C, as marked in the isothermal transformation diagram on next page. Answer the following questions. When it is cooled through 727 degree C the following reaction occurs: Pealitic reaction Eutectic reaction Eutectoid reaction Peritectic reaction At a temperature just below 727 degree C the equilibrium structure contains ferrite + cementite. The carbon contents of these two phases are approximately: 6.70%C in ferrite, 0.022%C in cementite 0.022%C in ferrite, 6.70%C in cementite 4.30%C in ferrite, 0.022%C in cementite 0.022%C in ferrite, 4.30%C in cementite At a temperature just below 727 degree C the equilibrium structure contains: 11 % ferrite + 89% cementite 89% ferrite + 11% cementite 40% ferrite + 60% cementite 83% ferrite + 17% cementite

Solution

A. Eutectoid reaction.

B. 0.022 % C in ferrite and 6.70 % C in cementite

C. 89% ferrite and 11% cementite.