What does the iron-carbon phase diagram represent?

The Fe – C diagram (also called the iron – carbon phase or equilibrium diagram) is a graphic representation of the respective microstructure states of the alloy iron – carbon (Fe-C) depending on temperature and carbon content. To explain this diagram, an introduction about metal structures and pure iron must be done.

What are the three important reactions that occur in iron-carbon phase diagram?

The invariant eutectoid reaction in Fe-Fe3C diagram is given by equation: i.e. during cooling, austenite of 0.77%C at constant eutectoid temperature, 727°C undergoes eutectoid transformation to form a mixture of ferrite (e = 0.02%) and cementite i.e. there are alternate lamellae of ferrite and cementite.

What is iron-carbon used for?

The purpose of adding carbon to iron is to change the properties of the iron. Carbon is a very hard substance and when it is added to iron, it becomes a much stronger material, depending on the amount of carbon added. Pure iron itself is relatively soft and ductile compared to carbon impregnated steels.

What is Curie temperature on iron-carbon equilibrium diagram?

The A2, point is the Curie point when iron changes from the ferro- to the paramagnetic condition. This temperature is 769°C for pure iron, but no change in crystal structure is involved.

What are the limitations of iron-carbon phase diagram?

10.9 Two limitations of the iron-iron carbide phase diagram are: 1) The nonequilibrium martensite phase does not appear on the diagram; and 2) The diagram provides no indication as to the time-temperature relationships for the formation of pearlite, bainite, and spheroidite, all of which are composed of the equilibrium …

Why iron carbon diagram is called equilibrium diagram?

The iron carbide is called meta stable phase. Therefore, iron-iron carbide diagram even though technically represents meta stable conditions, can be considered as representing equilibrium changes, under conditions of relatively slow heating and cooling.

What is the importance of iron-carbon diagram?

The iron-carbon phase diagram is widely used to understand the different phases of steel and cast iron. Both steel and cast iron are a mix of iron and carbon. Also, both alloys contain a small amount of trace elements.

What is the structure of 0.8 carbon steel at room temperature?

Steel containing 0.8% C is known as eutectoid steel. The equilibrium microstructure of eutectoid steel obtained at room temperature is pearlite (Fig. 6(c)) which is a mixture of two microconstituents named ferrite (α) and cementite (Fe3C); ferrite is very soft while cementite is a very hard constituent of steel.

Which is the hardest form of iron?

Steel and its alloys Steel is a tough alloy of iron and carbon with admixtures of other elements, including silicon, manganese, vanadium, niobium, etc. Various alloying techniques can help produce steels with completely different properties. Thus, a high-carbon steel is an iron alloy with a high carbon content.

Is Cementite FCC or BCC?

The alpha phase is called ferrite. Ferrite is a common constituent in steels and has a Body Centred Cubic (BCC) structure [which is less densely packed than FCC]. Fe3C is called cementite and lastly (for us), the “eutectic like” mixture of alpha+cementite is called pearlite.

Why do we need an iron carbon phase diagram?

The service life also improves as phase diagrams show us how to solve problems such as intergranular corrosion, hot corrosion, and hydrogen damage. The iron-carbon phase diagram is widely used to understand the different phases of steel and cast iron. Both steel and cast iron are a mix of iron and carbon.

What are the mechanical properties of iron carbon?

Mechanical properties of iron-carbon alloys (iron and steels) depend on their microstructure, that is, how the different phases are mixed. The iron –carbon phase diagram in Fig 2 actually shows two diagrams namely (i) the stable iron-graphite diagram (red lines), (ii) and the metastable Fe-Fe3C diagram.

Why is the carbon percentage of the iron-carbon equilibrium diagram 6?

In the following Iron-Carbon phase diagram, we can see that the maximum concentration of Carbon is 6.67%. This is due to the fact that maximum solubity of carbon in iron is 6.67% as it forms iron carbide (Fe3C form). At 6.67%, pure cementite (Fe3C) is present whereas at lower concentration other phases also occur.

Which is an interstitial impurity in the iron carbon system?

There are some important metallurgical phases and micro constituents in the iron carbon system. In the Fe–Fe3C system, carbon is an interstitial impurity in Fe. It forms a solid solution with alpha (alpha ferrite), gamma (austenite), and delta (delta ferrite) phases of iron. These are important phases in Fe – Fe3C phase diagram.