1. Microstructural investigations of 0.2% carbon content steel
Sajjad Tollabimazraehno
JKU – Johannes Kepler University
Linz, Austria
Christian Doppler Laboratory for
Microscopic and Spectroscopic Material Characterisation

2. Samples 0.2% Carbon, hypoeutectoid composition
Consider a composition to the left of the utectoid, between and 0.76 wt% C
Cooling an alloy of this composition vertical line

3. Sample 1 (S1): Martensite, 0.2% RA
Sample 2 (S2): temp. Martensite,0.3% RA
Sample 3 (S3): Bainite, 16.6% RA
Sample 4 (S4): 50% M, 50% B, 11.1% RA
Sample 5 (S5): 65%T.M, 5%B, 20%M, 8.2%RA
Sample 6 (S6): 65%T.M, 20%B, 5%M, 8.4% RA

4. Nano Indentation Hardness : S1 > S2 > S6 > S4 > S3 >S5
Sample 1 (S1): Martensite
Sample 2 (S2): temp. Martensite
Sample 3 (S3): Bainite
Sample 4 (S4): 50% M, 50% B
Sample 5 (S5): 65%T.M, 5%B, 20%M
Sample 6 (S6): 65%T.M, 20%B, 5%M
Hardness : S1 > S2 > S6 > S4 > S3 >S5

5. Electron Backscatter Diffraction: Grain Size
50 µm S3 S4 S5 S6

6. Phases S1 S2 S3 S4 S5 S6

7. Misorientation Angle Distribution
Kurdjomov-Sachs <111>α || <110>ɣ S5 S6
Nishiyama-Wassermann <110>α || <211>ɣ
A.-F. Gourgues, H. M. Flower, and T. C. Lindley Materials Science and Technology Jan Vol. 16

8. Grain boundaries S1 S2 S3 S4 S6 S5 Most boundaries have MA 47°-60°
Inside the grains with low MA
MA 60° related to twin relation

9. Conclusions
EBSD is very accurate to measure the grain size, even for fine microstrucutures like temp. martensite and provides information about larger areas than TEM
The hardness of samples is influenced by the grain size
The martensite variants were frequently twin related and formed from the same {111}ɣ.
The misorientation relationship in lower bainite and martensite were consistent with near Kurdjomov-Sachs orientation relationship.