PUNTOS INVARIANTES

Eutéctico (funde fácil): L -> S1 + S2

Peritéctico (funde alrededor): S1 + L -> S2

Monotéctico: L1 -> L2 + S

Peritectoide: S1 + S2 -> S3

Eutectoide: S1 -> S2 + S3

Punto de Fusión Congruente: L -> S

Punto de Transformación Congruente:

S1 -> S2

EJEMPLO: CU - SN

1. Peritéctico: L+Cu ->

2. Peritéctico: L+ ->

3. PTE ->

4. Eutectoide: -> Cu5. Eutectoide: -> + Cu

12

6

34

56. Peritéctico: L+ ->

A 300 °C y una composición de 50% Sn, ¿cuáles son las fases presentes y en qué cantidades?

Reacción Peritéctica: L+δ -> γ

Reacción Eutéctica: L -> γ+Fe3C

Phase equilibria in the Fe-C system

+ Fe3C +

+ Fe3C

912

T(ºC)

727

wt% C0.02 0.776.69

Fe3C

A1

A3

Acm

What type of invariant

reaction is this?Eutectoid

Nucleation and growth

C1

Let’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growthLet’s consider the cooling of a single phase austenite through the intercritical regime.

C1

Nucleation and growth

Now we examine a similar case for a higher carbon content.

C1

Nucleation and growth

Now we examine a similar case for a higher carbon content.

+Fe3C

C1

Nucleation and growth

Now we examine a similar case for a higher carbon content.

When we cross the A1, the remaining austenite transforms to a two-phase product of and Fe3C, known as pearlite.

Resulting Microstructures

Ferrite

Pearlite

Eutectoid transformation

The pearlite reaction in Fe-C-alloys

Eutectoid transformation at 0,8% C: CFe3