Microstructure Constituents

Austenite
1. Face-Centred Cubic
2. In Iron-Carbon Alloys
  1. Evident between 723°C and 1500°C
3. Can be Retained at Room Temperature by Alloy Additions Such as Nickel or Manganese
4. Former by Cooling from a Liquid State
Martensite
1. Formed when Cooling Rate from Austenite is Sufficiently Fast
2. Very Hard Constituent due to the Carbon which is Trapped in the Solid Solution
3. Occurs by Sudden Diffusionless Shear Process
4. Term not limited to steel
Bainite
1. Formed at cooling rates slower than that for martensite formation but faster than that for ferrite and pearlite formation
2. Two Forms
  1. Upper Bainite
    1. Forms between 550°C and 400°C
  2. Lower Bainite
    1. Forms between 400°C and 250°C
Pearlite
1. Formed During the Slow Cooling of Iron Alloys
2. Can Begin at a Temperature of 1150°C to 723°C Depending on the Composition of the Alloy
3. Formed by Eutectoid Decomposition of Austenite Upon Cooling by Diffusing of C Atoms when Ferrite and Cementite Grow Continuously

Resource summary

	Created by Billie Juniper over 9 years ago