1545

1

2

3

1. ECTECTIC

2. PERITECTIC

3. EUTECTOID

1537

Cementite Fe3C

Fe- C diagram- REGIONS

HY

PO

EU

TE

CT

OID

HY

PE

RE

UTE

CTI

C

HY

PE

RE

UT

EC

TO

ID

STEEL CAST IRON

1131

723

0.8

2 4.3

15451537

0.16

1493

6.7H

YP

OE

UTE

CTI

C

Fe- C diagram- simplified

RP Q

C

100 Fe

Austenite+cementite- LEDEBURITE

Ferrite + Cementite- PEARLITE

MARTENSITE- a metastable phase of steel- by quenching- highly stressed α iron supersaturated with carbon

EUTECTIC REACTION

EUTECTIC TEMPERATURE

LIQUID

α+ β

Location 1- Eutectic Reaction

PERITECTIC REACTION

Liquid + β

α

Peritectic Temperature

PERI in Greek- Around

Location 2- Peritectic Reaction

δ Iron - BCC -

γ Iron – FCC - AUSTENITE

EUTECTIOD REACTION

SOLID 1

SOLIDS 2 & 3

EUTECTIOD TEMPERATURE

Location 3- EUTECTOID REACTION

0.8% C

FERRITE

α +γ

γ

FERRITE +

CEMENTITE

δ Iron - BCC – Max. solubility of 0.1% at 14930C

γ Iron – FCC – AUSTENITE- max. solubility of 2% at 11310C

α Iron – BCC- max. solubility of 0.22% at 7230 C – FERRITE

Fe3C –CEMENTITE - 100% iron carbide - Intermetallic Compound - From Latin caementum, meaning stone chips. –

7230C

9100C

Unit cells

Austenite Ferrite Martensite

FCC BCCRECT.PRISM- BC Tetragonal

Effect of carbon % (by weight) on lattice dimensions

Fe atomC atom

Carbon%

c (nm) a (nm)

0 0.286 0.286

0.20 0.288 0.2858

0.40 0.291 0.2856