WIT Press

MIG Welding Of Aluminium Matrix Composites. Weldability And Post Welding Heat Treatments.


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J. M. Gomez de Salazar & M. I. Barrena


Metal matrix composites reinforced with A1203particles combine the properties of the matrix (ductility and toughness) with the ceramic properties of the reinforcements (high strength) and they have been used profusely in different industries. However, their wide application as structural materials requires proper development of their joint process. The present work describes the results obtained from microstructural evaluation, both with optical and scanning electronic microscopy (OM and SEM, respectively), and from mechanical evaluation (Hardness profiles and stress strain changes) of the weld produced in the materials using GMAW (MIG) welding process. The filler metal used has a composition of AI-5Mg (AA5356). A characteristic of the welding carried out in composites, when compared to welds made under the same condition using materials with out reinforcement, is that the size of the welding pool is greater in the composite materials. This is due to the lower thermal conductivity of the composites, which means that heat is dissipated more slowly from fusion zone thus allowing a greater quantity of the base material to melt. Furthermore, the composites act as insulator and therefore reduce the cooling rate of the bath. The thermal effect of welding on different types of joint results in a loss in the mechanical properties of the heat affected zones (HAZ). These properties can be recover with post welding heat treatment.