What is pearlite transformation?

The pearlite transformation involves the redistribution of carbon followed by a structure change, the martensite transformation involves the structure change alone, and, in contrast, the bainite transformation involves a structure change followed by the redistribution of carbon, which precipitates as a carbide.

What is transformation of austenite?

Austenite transforms to a new metastable phase called martensite, which is a supersaturated solid solution of carbon in iron and which has a body-centered tetragonal crystal structure.

What is the equilibrium temperature of transformation of austenite to pearlite?

The Si content of high-Si nodular graphite cast iron is about 14%, which raises the eutectoid transformation temperature (723 °C, the transformation temperature from austenite to pearlite).

What is the difference between austenite and pearlite?

As the overall content of carbon increases, the proportion of pearlite becomes higher and the bulk strength increases. 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.

What is austenite to pearlite transformation?

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). Pearlite is a microstructure occurring in many common grades of steels.

How 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).

Which is are the transformed products of austenite?

In eutectoid reaction, solid austenite transforms to two solid phases forming a lamellar (eutectic) structure. The lamellas are cementite lamellas and α-ferrite lamellas.

What is different about the martensitic transformation of austenite compared to the pearlite transformation of austenite?

Like martensite, pearlite is created by quenching steel, usually with water or oil. However, the key difference between it and martensite lies in the rate at which it is cooled. Pearlite is cooled more slowly than its martensite counterpart, making it softer and easier to bend.

How is austenite formed?

Austenite only forms when an iron-based alloy is heated above about 750°C (1382°F) but not above about 1450°C (2642°F). Austenite keeps its form at room temperature when special alloying elements have been added to the iron-based alloy.

What are the differences in the properties of pearlite and martensite steels?

What is a key characteristic of the transformation of austenite to martensite?

The original horizontal surface of austenite is tilted into new orientation by shear transformation and is easily seen as surface relief that occurs. Surface tilting, or relief is an important characteristic of martensitic transformation.

What is the structure of pearlite?

Pearlite is a two-phased, lamellar (layered or plate-like) structure composed of alternating layers of alpha-ferrite and cementite that occurs in some steels and cast irons. Pearlite only forms under specialized conditions which must be controlled to create this alloy phase.

What is a pearlite microstructure?

Pearlite is a common microstructure occurring in many grades of steels. It is hard and strong because of the layered structure, and is used in a variety of applications. Pearlite is wear-resistant because of a strong lamellar network of ferrite and cementite.

What is the microstructure of austenite?

Austenite has a cubic-close packed crystal structure, also referred to as a face-centred cubic structure with an atom at each corner and in the centre of each face of the unit cell. Ferrite has a body-centred cubic crystal structure and cementite has an orthorhombic unit cell containing four formula units of Fe3C.

What is pearlite microstructure?

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.

What is austenite microstructure?

What is the kinetics of the austenite-to-pearlite transformation?

The kinetics of the austenite-to-pearlite transformation obeys the Avrami relationship (y ൌ1 െ expሺെkt୬ሻ). Using the fraction transformed–time data given here, determine:/2/2 /2 Note to the grader: There was a typo in part b.

How long does it take austenite to transform to pearlite?

The kinetics of the austenite-to-pearlite transformation obey the Avrami equation and that the value of n in the exponential is 2.5. If, at some temperature, the fraction transformed-time data given here, determine the total time required for 95% of austenite to transform to pearlite: Fraction Transformed Time (s) 0.2 12.8 0.8 28.5

How many stable nuclei are there in the austenite-to-pearlite transformation?

The kinetics of the austenite-to-pearlite transformation obeys the Avrami relationship (y ൌ1 െ expሺെkt୬ሻ). Using the fraction transformed–time data given here, determine:/2/2 /2 Note to the grader: There was a typo in part b. Some students considered the number of stable nuclei to be 106. Please do not deduct point in this case.