H. Variation of RA Content Welded TRIP Steels
Table III shows the volume fraction of RA present in
the base metal, HAZs, and FZs of high-Si and high-Al
TRIP steels measured by X-ray diffraction analysis.
It can be seen from the table that very little austenite
is stabilized within the FZs of TRIP steels. This is due to
the fact that formation of complex inclusions during
welding of TRIP steels leaves very low concentrations of
dissolved alloying elements such as silicon and aluminum
in the weld pool to stabilize the austenite. Due to
this, the purpose of silicon and aluminum additions is
lost, because they are no longer effective in suppressing
the formation of iron carbides. This ultimately leads to
the depletion of dissolved carbon in the weld pool,
which results in less austenite in the FZs.