Prakt. Met. Sonderband 38 (2006) 249 
Laser hybrid, (g) fh 
MT, MIG 
‘1.2 mm 
n (tab. 1). 
croscopy, Cw I 
scattered pT sum 0 Sum 2 
5. Vickers Parent Material Interface Weld Seam 
step size Weld Seam / Parent Material 
Jd down to Fig.2: Microstructures at the cross-sections of the welded samples 
standard 
Microstructure. The microstructure of CMT AlMg3- 
butt-joints appears to be very similar to that 
produced by MIG and laser hybrid welding (Fig.2). 
p [KW] The porosity in the fusion zone (FZ) is similar for 
- the CMT and the laser-hybrid welds, however, 
== slightly higher for the MIG weld (Fig.1). 
2.7 The AIMg3-parent material in all investigated butt- 
N 
Voltage in joints consists basically of equiaxed a-Al grains 
(Fig.2a,d,g) with an average grain size of 22um 
and a bimodal dispersion of precipitates 
ent G3 at (Fig.3a,b). SEM investigations of the base material 
ngitudinal reveal two kinds of coarse intermetallic phases 
using the with sizes ranging from 1.0-5.0um: Mg,Si (dark 
using the particles, Fig. 3a) and AlsMn (bright particles, 
Fig.3a). A second population of smaller (0.05- 
0.5um size) MgzSi- and AlsMn-particles is visible 
in TEM images(Fig.3b). 
SEM studies of the weld/parent material interface 
[a show that, the precipitate size remains the same 
be next to the FZ of the CMT and laser hybrid welds. a 
ond Consequently, a heat-affected zone (HAZ) can not fz... To kamen 
ay be defined (Fig.2b,h). This is probably due to the  Fig.3: SEM and TEM micrographs 
re reduced heat input for the CMT welding and the show coarse and fine precipitates. 
vr optimization of laser power as well as respectively, in the AIMg3-parent 
Sin material 
; 50 ums voltage/current for the laser hybrid 
a technique. In contrast, a narrow HAZ (about 
50um wide) becomes apparent for the MIG 
weld at the SEM (see arrow, Fig.4). 
CMT, MIG and laser hybrid welding led to 
the formation of a dendritic microstructure 
within the weld pool. The average grain size 
increases to 57um in the FZ 
(Fig.2b,c,e,f,h,i). The AISi5-filler induced the 
50 um £ formation of numerous segregated zones at 
nn grain boundaries and the formation 
Fig.4: Precipitation coarsening within the HAZ of intermetallic precipitates (Fig.5,6). Fig.7 
the MIG weld displays a detailed EBSD analysis of a 
1