C. Microstructural Characteristics

C. Microstructural Characteristics of Welded Steel
Plates
The average grain size in the coarse-grained zone in
both steels is about 120 lm (Figure 4). The FZs and
HAZs of GTA-welded TRIP steels contain primarily a
martensitic structure. Unlike the high-Al steel weld, the
coarse-grained HAZ in the high-Si steel did not show
the presence of allotriomorphic ferrite at the fusion line
and grain boundaries.
The FZs of both steels show the presence of inclusions,
mainly with a random distribution and in some
places decorating the grain boundaries. The average
sizes of the inclusions in the FZ of the high-Si steel are
found to be smaller in size compared with those found in
the high-Al FZ. A zone of soft allotriomorphic ferritic
grains was found across the fusion line of the high-Al