250 Prakt. Met. Sonderband 38 (2006) 
segregated zone. All alloying elements (Mg,Si,Mn and Fe) strongly segregate into these 
zones during the solidification interval due to the higher solubility of the alloying elements 
within the liquid aluminum. However, Mg and Si remain dissolved within an a-Al solid 
solution, whereas Mn and Fe build very fine Al4(Mn,Fe)-precipitates. 
Vickers microhardness tests were performed in order to assess the local mechanical 
properties of the AIMg3-butt-joints. The microhardness profiles (Fig.8) are very similar for 
all welds investigated and show an increase of 
mechanical strength from 70 HVO0.1 in the AIMg3- 
parent material to 90 HV 0.1 in the fusion zone. 
The HAZ is, however, very narrow to be detected 
by microhardness measurements. The hardness 
values are higher in the weld seam presumably 
due to the increased volume fraction of 
precipitates/segregations observed. or 
ote 
105 ~ IP 
_ Bad] o-Al Matrix 
° ZZ Intermetalics + Segregation | Cr) 
mn 10€ " TA ve 
en 
95 bo 
90 the 
dil 
8 
80 
Parent Material Welk 
Fis SE Fig.6: Volume fraction of intermetallic phases 
CL and/or segregations for the AIMg3-parent 
Fig.5: Segregations and precipitates material and the fusion zones 
at grain boundaries in the CMT- 
fusion zone 
Total 
Phase Fraction 
ASTMN1Z 0048 
Mg2Si 0.000 
Mg5Si6 0.008 th 
Alıyminum N a4? as 
Fig.7: EBSD element and phase maps of the CMT fusion zone of