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