Table of Contents
Why is pearlite formed?
Pearlite is usually formed during the slow cooling of iron alloys, and can begin at a temperature of 1150°C to 723°C, depending on the composition of the alloy. It is usually a lamellar (alternate plate) combination of ferrite and cementite (Fe 3C).
What is the difference between austenite and pearlite?
Ferrite is soft and ductile, while pearlite is hard and brittle. Austenite is a high-temperature phase of plain steel, which recrystallizes into ferrite/pearlite around 1425°F (depending on chemistry), below which ferrite becomes the more stable phase.
Why does the layered structure form in pearlite?
Once the steel is cooled below the eutectoid temperature the remaining austenite, now of the eutectoid carbon content, transforms to pearlite, which consists of alternating layers of cementite and ferrite. The amount of pearlite in the structure increases with increasing carbon content.
Where is pearlite formed?
eutectoid point
Pearlite is formed during sufficiently slow cooling in an iron-carbon system at the eutectoid point in the Fe-C phase diagram (723 °C, eutectoid temperature).
What is pearlite made of?
Pearlite is a mixture of ferrite and cementite forming distinct layers or bands in slowly cooled carbon steels. Pearlite is an iron alloy that contains around 88\% ferrite and 12\% cementite.
What is ferrite pearlite austenite?
The gamma phase is called austenite. Austenite is a high temperature phase and has a Face Centred Cubic (FCC) structure [which is a close packed structure]. 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].
What is perlite in metallurgy?
Pearlite is a mixture of ferrite and cementite forming distinct layers or bands in slowly cooled carbon steels. Pearlite is an iron alloy that contains around 88\% ferrite and 12\% cementite. Pearlite is known for being tough and it is used in a variety of applications, including: Cutting tools. High-strength wires.
How is coarse pearlite formed?
During slow cooling of an iron-carbon alloy, pearlite forms by a eutectoid reaction as austenite cools below 723 °C (1,333 °F) (the eutectoid temperature). It makes pearlite one of the strongest structural bulk materials on earth.
Is pearlite 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 does pearlite form a lamellar structure?
During slow cooling pearlite forms by a eutectoid reaction as austenite is cooled below 727°C (the eutectoid temperature). An intimate mixture with ferrite, the other product of austenite, forms a lamellar structure called pearlite.
What is pearlite in metallurgy?
Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt\%) and cementite (12.5 wt\%) that occurs in some steels and cast irons.