the effect of carbon content of the mechanical properties - McMaster ...

M.A.Sc. Thesis – E. E. Yang McMaster – Materials Science & Engineering
the same consistency true for the 0.4C and 0.2C alloys. The kinematic hardening was
seen to contribute significantly to the overall flow stress indicating that the interaction of
dislocations with the deformation products represents a major contribution to the
hardening of the alloys. The response for the true strains observed (0 to εt=0.30) and the
hardening response for εt>0.30 was not explored.
For the 0.6C alloy, from the SFE estimations, these deformation products were
predicted to be mechanical twins and later confirmed with EBSD phase maps. The
calculated kinematic hardening response shown in Figure 5.10 for the 0.6C alloy
displayed a large portion of the flow stress to the kinematic hardening.
The 0.4C alloy kinematic hardening trend was similar to the 0.6C with a
significant portion of kinematic hardening contributing to the total flow stress. The
calculated back stress for the 0.4C alloy, displayed in Figure 5.11, revealed the back
stress possibly beginning to saturate for εt > 0.30 due to a limited amount of deformation
products within this alloy. This was further discussed after XRD and EBSD analysis.
The 0.2C alloy displayed a kinematic hardening response per Figure 5.12 with the
curve displaying a different trend compared with the other two alloys. The 0.2C began to
turn over (saturate), and contributed less to the overall flow stress with back stress values
increasing at a lower rate, indicating that the deformation products produced had a
reduced contribution to the work hardening and were becoming saturated with
dislocations prior to 0.30 true strain.
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