900

1
900 C
25C/s
10 C/s
Temperature
250 - 350 C
50 C/s
1800 s
15s
4 - 200 MPa
Stress
4 MPa
Time
Fig. 1 The form of the thermomechanical
treatment, used to study stress-affected bainite.
Fig. 2 Experimentally determined 0.2 proof
strength of the austenite as a function of test
temperature.
2
-1800
?GMECH
-1600
?GCHEM
-1400
-1200
-1000
Free energy / J mol-1
-800
-600
-400
Stored energy of bainite
-200
0
250
º
C
300
º
C
350
º
C
Umemoto
Shipway
et al. 12
et al. 13
at 360
º
C
at 350
º
C
Fig.3 Chemical and mechanical components of the
driving force for the growth of bainite.
3
(a)
(b)
Fig.4 Change in radial strain associated with
the bainite transformation (a) at various
transformation temperatures and (b) as a function
of elastic stresses during transformation at 300
ºC.
4
Fig.5 Volume percent of bainite as a function
of stress applied during the transformation, and
the transformation temperature.
Fig. 6 Transformation kinetics at various
transformation temperatures and stresses.
5
4 MPa
200 MPa
0.5 h
1 h
2 h
Fig. 7 Optical micrographs of bainitic
microstructure transformed under the influence
of an applied compressive stress. The stress
axis is vertical in each case. The
transformation is at 300 ºC.
6
4 MPa
200 MPa
350 ºC, 5 h
300 ºC, 5 h
250 ºC, 12 h
Fig. 8 Optical micrographs of bainite
transformed under the influence of an applied
compressive stress. The stress axis is vertical
in each case.
7
Fig. 9 Typical scanning electron micrographs of
bainite transformed under the influence of an
applied stress (a) 4 MPa and (b) 200 MPa at 300
C for 5 hours. The stress axis is vertical in
each case.
8
Fig.10 Approximate distribution of bainite sheaf
traces with respect to longitudinal axis of
sample.
9
Fig.11 Orientation imaging maps of bainite
formed at 300 ºC for 5 hours under the influence
of an applied compressive stress of (a) 4 MPa
and (b) 200 MPa. The stress axis is vertical in
each case.