Iron- Carbon Phase Diagram

Iron-Carbon Phase Diagram
Its defined as:-
A map of the temperature at which different phase changes occur on very slow heating and cooling in relation to Carbon content . is Isothermal and continuous cooling transformation diagrams for plain carbon and alloy steels.

Iron- Carbon diagram shows
1- the type of alloys formed under very slow cooling.
2- Proper or ( suitable ) heat-treatment temperature .
3- the properties of steels and cast irons can be depend on changed by heat-treatment.

In their simplest form, steels are alloys of Iron (Fe) and Carbon (C).

Notes: -
This graph, which is known as iron- carbon equilibrium diagram has the following important points: -

1- The percentage of carbon is between 0% and 6.67%. Because:-
• 6.67 % carbon is maximum ratio of carbon can be dissolved in iron.
• after 6.67 % carbon , all metallic alloys are non-important alloys in engineering applications .

2- Iron contains from (0% to 1.7% C ) known as steel.

3- Steel contains below approximately ( 0% to 0.83 % C) known as hypoeutectoid steel consist of primary ferrite and pearlite phases .

4- Eutectoid steel (carbon content 0.83%) entirely consists of pearlite.

5- steel contains from (0.83% to above 1.7 % C) known as hypereutectoid steel consist of primary cementite and pearlite phases .

6- Iron contains carbon more than 1.8 % C known as cast iron.

Types of iron-carbon equilibrium diagrams:
1- stable iron-graphite Fe-Gr.
The stable condition usually takes a very long time to develop.

2- metastable iron-cementite Fe-Fe3C
While The metastable diagram is of more interest or important .