Eutectoid Steel and Microstructures

The video tutorial explains TTT diagrams, focusing on their use in understanding phase transformations in iron-carbon steel with eutectoid composition. It covers the eutectoid reaction, the role of temperature, and the formation of different microstructures like pearlite, martensite, and bainite. The process of quenching and its impact on steel microstructure is also discussed.

What does the third 'T' in TTT diagrams stand for?

• Time

• Temperature

• Transformation

• Tension

What is the carbon composition of eutectoid steel?

• 1.00 weight percent

• 0.76 weight percent

• 0.50 weight percent

• 1.50 weight percent

At what temperature does the eutectoid reaction occur?

• 800°C

• 727°C

• 600°C

• 500°C

What is the symbol for ferrite in the eutectoid reaction?

• Beta

• Gamma

• Alpha

• Delta

What phase does austenite transform into below the eutectoid temperature?

• Martensite

• Bainite

• Ferrite

• Pearlite

What is the stable phase of eutectoid steel above the eutectoid temperature?

• Ferrite

• Austenite

• Bainite

• Martensite

What happens to austenite when it is rapidly cooled?

• It forms pearlite

• It forms martensite

• It forms bainite

• It remains austenite

What happens if steel is quenched in less than a second?

• It remains unchanged

• It forms bainite

• It forms martensite

• It forms pearlite

What microstructure is formed when steel is cooled to 350°C and held for 2000 seconds?

• Martensite

• Pearlite

• Bainite

• Austenite

What is the appearance of bainite compared to pearlite?

• Granular

• Dendritic

• Fibrous

• Lamellar