| Summary: | Welding of metal matrix composites (MMCs) is an alternative to their
mechanical joining, since they are difficult to machine. Published literature in fusion
welding of similar composites shows metallurgical problems. This study investigates the
weldability of A359/SiC/10p aluminum SiC MMC. Statistical experiments were
performed to identify the significant variables and their effects on the hardness, tensile
and bending strengths, ductility, and microstructure of the weld. Finite Element
Analysis (FEA) was used to predict the preheat temperature field across the weld and the
weld pool temperature.
Welding current, welding speed, and the preheat temperature (300-350??C)
affected the weld quality significantly. It was seen that the fracture of the welded
specimens was either in the base MMC or in the weld indicating a stronger interface
between the weld and the base MMC. Oxides formation was controlled along the weld
joint. Low heat inputs provided higher weld strengths and better weld integrity. It was
found that the weld strengths were approximately 85% of the parent material strength.
The weld region had higher extent of uniform mixing of base and filler metal when
welded at low currents and high welding speeds. These adequate thermal conditions
helped the SiC particles to stay in the central weld region. The interface reaction
between the matrix and SiC particles was hindered due to controlled heat inputs and
formation of harmful Al4C3 flakes was suppressed. The hardness values were found to
be slightly higher in the base metal rich region. There was no significant loss in the
hardness of the heat affected zone. The ductility of the weld was considerably increased
to 6.0-7.0% due to the addition of Al-Si filler metal.
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