Phase Transformation Fe-C

Question 1

Martensite to Spheroidite

Answer 1

~700ᵒC long time

Question 2

Spheroidite to Martensite

Answer 2

Heat above Tₑ + quench

Question 3

Bainite to Pearlite

Answer 3

Heat above Tₑ + cooling rate < 35 ᵒC/s

Question 4

Pearlite to Bainite

Answer 4

Heat above Tₑ + quench to 400ᵒC + hold

Question 5

Spheroidite to Pearlite

Answer 5

Heat above Tₑ + cooling rate < 35 ᵒC/s

Question 6

Pearlite to Spheroidite

Answer 6

~700ᵒC long time

Question 7

Tempered Martensite to Martensite

Answer 7

Heat above Tₑ + quench

Question 8

Bainite to Spheroidite

Answer 8

~700ᵒC long time

Question 9

Cite two reasons why martensite is so hard and brittle

Answer 9

① BCT has a fewer slip system = dislocation movement is impeded
② Solid solution hardening due to the strain field contribution of C atoms

Question 10

How does tempering recoverers the loss ductility

Answer 10

by reducing the stress caused by quenching

Question 11

How can to obtain course pearlite? fine pearlite?

Answer 11

fine pearlite = fast cooling = grains no time to grow

coarse pearlite = slow cooling = grains have time to grow