Prakt. Met. Sonderband 38 (2006) 251
ito these Texture. Texture formation in the FZ was
elements 105] examined using EBSD. Due to the coarse
-Al solid N po -m—CMT grain size in the FZ, the scanned region by
"ga Ne EBSD was extended up to 1x3mm?. The
xchanical 85 EBSD analyses reveal two distinct grain
imilar for 80 morphologies (Fig.9, CMT). From the
rease of A kt edges with the parent material, elongated
Ty Wr. .
> AIMg3- 65 ; grains grow toward the weld pool, whereas
on zone. & 60] in the weld centre the grains become more
detected AA | equiaxed. Fig.8 is a so-called Inverse
hardness 8 6 4 2 0 2 4 6 8 PoleFigure (IPF)-map along TD
sumably Distance to the weld center [mm] (perpendicular to the weld line), i.e. the
;tion of Fig.8: Microhardness profile across the welds color levels represent the crystallographic
orientations of grains with respect to the stereographic
standard triangle along the TD-specimen direction. From the
IPF-map along TD it is also apparent, that a certain
crystallographic texture exists in the FZ but it is in general not
very sharp. Fig.10 shows the pole figures obtained for the
entire FZ (Fig.10a) and for the elongated grains at the weld
boundaries (Fig.10b). In both cases the (100) lattice plane is
the texture pole, which appears tilted around the welding
direction (WD) (a ~ 80°) and rotated around ND (8 ~ 10°). The
(a) maximum texture strength for [010] TD
199 19 the entire FZ amounts to 2.9. sum
© Bol However, if the elongated
/ @ of Bete grains at the weld boundaries
hases PP WV are considered separately, the
int i de texture strength increases up —
iki to a maximum of 3.4 (Fig.10b). Fig.9: IPF-map of CMT
183 i This kind of crystallographic ~~ weld in the transversal
Era texture reflects the effect of the direction
WV te — vectorial heat flow during the
N m solidification process on the orientation of grain growth
(b) 100 110 within the weld pool. Thus, the (100) lattice planes with the
SP , oc lowest surface energy in case of fcc-metals will grow
an AS Sm preferentially along the heat flow direction [8,9]. The heat
Co ©
J
0»
© 3 cr
Fig.11: Scheme of the heat flow within the fusion zone
Fig.10: Pole figures
obtained for the CMT weld
flow, on the other hand, presumably occurs toward the
three main specimen directions WD, TD and ND (fig.11) due to the low depth-to-width
aspect ratio of the investigated welds (maximum 1.5). Thus, the true spatial arrangement
of the vector of heat flow (hy) is defined by the magnitudes of heat flow occurring along
WD, TD and ND. Therefore, the <100> crystal direction coincides with h; in the FZ.