Welding of cast A359/SiC/10p metal matrix composites

摘要

Welding of metal matrix composites (MMCs) is an alternative to theirmechanical joining, since they are difficult to machine. Published literature in fusionwelding of similar composites shows metallurgical problems. This study investigates theweldability of A359/SiC/10p aluminum SiC MMC. Statistical experiments wereperformed to identify the significant variables and their effects on the hardness, tensileand bending strengths, ductility, and microstructure of the weld. Finite ElementAnalysis (FEA) was used to predict the preheat temperature field across the weld and theweld 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 weldedspecimens was either in the base MMC or in the weld indicating a stronger interfacebetween the weld and the base MMC. Oxides formation was controlled along the weldjoint. Low heat inputs provided higher weld strengths and better weld integrity. It wasfound 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 whenwelded at low currents and high welding speeds. These adequate thermal conditionshelped the SiC particles to stay in the central weld region. The interface reactionbetween the matrix and SiC particles was hindered due to controlled heat inputs andformation of harmful Al4C3 flakes was suppressed. The hardness values were found tobe slightly higher in the base metal rich region. There was no significant loss in thehardness of the heat affected zone. The ductility of the weld was considerably increasedto 6.0-7.0% due to the addition of Al-Si filler metal.