P UNTOS I NVARIANTES  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

E JEMPLO : C U - S N 1. Peritéctico: L+Cu ->  2. Peritéctico: L+  ->  3. PTE  ->  4. Eutectoide:  ->  Cu 5. Eutectoide:  ->  + Cu 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+Fe 3 C

Phase equilibria in the Fe-C system  + Fe 3 C  +   + Fe 3 C 912 T(ºC) 727 wt% C Fe 3 C A1A1 A3A3 A cm What type of invariant reaction is this? Eutectoid

Nucleation and growth  C1C1 Let’s consider the cooling of a single phase austenite through the intercritical regime.

  C1C1 Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

  C1C1 Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

  C1C1 Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

 C1C1  Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

C1C1   Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

C1C1  Nucleation and growth Let’s consider the cooling of a single phase austenite through the intercritical regime.

 C1C1  Nucleation and growth Now we examine a similar case for a higher carbon content.

C1C1   Nucleation and growth Now we examine a similar case for a higher carbon content.

 +Fe 3 C C1C1  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 Fe 3 C, known as pearlite.

Resulting Microstructures Ferrite Pearlite

Eutectoid transformation The pearlite reaction in Fe-C-alloys Eutectoid transformation at 0,8% C: