Welding of Al-359/20%SiCp metal matrix composites by the novel MIG process with indirect electric arc (IEA)

An Al-based composite reinforced with 20%SiCp was welded using the MIG welding process with direct and indirect application of the electric arc (DEA and IEA respectively). The welds were made on 12.5 mm thick plates in three welding passes for the DEA joint whereas only one pass was required for the IEA joint. Microstructural examination of the joints revealed DEA welds with light signs of matrix/reinforcement reaction whilst in the IEA welds the SiC particles remained with their initial angular morphology. Mechanical failure occurred consistently and independently of the type of joint in the weld zone and the measured strengths were 209 and 234 MPa for DEA and IEA welds respectively. The greater strength measured for the IEA weld was due to reduced porosity and good incorporation and dispersion of the SiC particles into the weld pool.