مقاله جوشکاری با عنوان : Characterization of microstructure and deformation behaviour of resistance spot welded AZ31 magnesium alloy

N. Kishore Babua,∗, S. Brauserb, M. Rethmeierb,c, C.E. Crossd

چکیده : 

Resistance spot welds were prepared on 3 mm thick sheets of continuous cast and rolled AZ31 magnesium
alloy. The microstructure and composition analysis of weld nugget, heat affected zone (HAZ)
and base metal were examined using optical and scanning electron microscopy (HR-SEM and EDS/X).
The resistance spot welded magnesium alloy joints consist mainly of weld nugget and HAZ. The nugget
contains two different structures, i.e. the cellular-dendritic structure at the edge of the nugget and the
equiaxed dendritic structure in the centre of the nugget. The structure transition is attributed to the
changes of solidification conditions. In the HAZ, grain boundary melting occurred and grain boundaries
became coarse. It has been shown that hardness reduction in the weld nugget and HAZ compared with
base metal is evident due to dendritic microstructure and grain growth, respectively. The results showed
that spot welded joints have failed in interfacial mode under torsion and tensile–shear loading conditions.
Digital image correlation during tensile–shear testing showed that low surface strains occur in the
interfacial failure mode, because fracture and deformation happened primarily in the nugget area.