4. 1 µm

6. Surface Surface 2
50 µm
Srinivasan & Wayman, 1968

7. s d c r 1

10. 50 µm

12. Carbon supersaturated plate
Carbon diffusion into
Carbon diffusion into
austenite
austenite and carbide
precipitation in ferrite
Carbide precipitation
from austenite
UPPER BAINITE
LOWER BAINITE
(High Temperature)
(Low Temperature)

13. Decarburisation time / s1 2
Fe-0.4C wt%
Decarburisation time / s
500
400
300
Temperature / °C

15. Temperature
Ae3' T' o x
Carbon in austenite

17. Summary The mechanism of transformation is displacive
Transformation temperatures higher than martensite
Bainite grows without diffusion
But carbon then escapes into the residual austenite
Shape deformation plastically accommodated
Sub-unit mechanism of growth

18. DISPLACIVE
RECONSTRUCTIVE

28. Summary
Mechanism of transformation is displacive but carbon must partition during growth.
Pairs of plates grow together to minimise strain.