PRESENTED BY

ABHIJEET CHOUDHARI

Three Phase Reactions

Peritectic, at 1492°C, with low % of Carbon in

alloys. (almost no engineering importance).

Eutectic, at 1147°C, with 4.3% Carbon, alloys

called cast irons.

Eutectoid, at 727°C with eutectoid

composition of 0.8% Carbon, having two-

phase mixture (ferrite & cementite). They are

steels.

Eutectic, Eutectoid, & Peritectic:

• Peritectic - liquid and one solid phase transform to a 2nd. solid phase

Solid1 + Liquid ↔ Solid2

+ L ß

Eutectic - liquid transforms to two solid phases

L +

• Eutectoid – one solid phase transforms to two other solid phases

Solid1 ↔ Solid2 + Solid3

+ Fe3C + α

Eutectoid reaction

Redistribution of carbon by diffusion

Austenite – 0.76 wt% CFerrite - 0.022 wt% CCementite - 6.70 wt% C

Pearlitey↔α+ Fe3C

Simplified Iron-Carbon phase diagram austenite ↔ pearlite (mixture of ferrite & cementite)

Nucleation & growth of pearlite

Schematic picture of the formation and growth of pearlite

Ferrite (α) Cementite

Principal phases of steel and their Characteristics

SUMMARY

Basically in Eutectoid reactions, a single solid

converts into two different solids while

cooling at Eutectoid temperature.

eg: Fe-C, Cu-Sn, Cu-Al, Zn-Al, Al-Mn, etc.

ANY QUARIES.......

Referances....

• Material science & Metallurgy By V.D. Kodgire, S.V. Kodgire.

• Google, Wekipedia.

THANK YOU…!