Welding technology of metal matrix composites

Due to their high specific-strength, SiC reinforced aluminum metal matrix composites (Al/SiC-MMCs) are becoming popular for wide range of applications including vehicles, aircraft, rockets and shipbuilding. It is difficult to fusion weld such material due to porosity and aluminum carbide (Al4C3) formation in weld zone (WZ) which result in degradation of mechanical properties of the welded joints.In this study, several sets of Al/SiC-MMCs samples having 0, 5, 15 and 20 vol.% SiC particulates were fabricated by powder metallurgy technique using hot compaction of Al and SiC powders followed by hot extrusion. Effect of welding conditions such as heat input, filler wire type (ER4043 and non-commercial AlTi5B1) and without filler using AC-GTAW (TIG) process was studied to find out appropriate conditions to get sound welded joints.Microstructure for weld zone was examined using optical and scanning electron microscope (SEM). Phases were identified and analyzed using x-ray diffraction (XRD) and energy dispersive x-ray (EDX) analysis. It was found that porosity and Al4C3 formed in WZ during welding without filler and with ER4043 filler. Using AlTi5B1 alloy which is used as a grain refinery in aluminum industry as a welding filler. Porosity were reduced and Al4C3 suppressed at 20 vol. % SiC and 5.86Kj/cm heat input. Hardness values in WZ remain as high as base metal when using AlTi5B1 filler, whereas it drastically reduced when welding without and with ER4043 filler. The new filler wire of AlTi5B1 was used for the first time in welding Al/SiC-MMCs and proved as promising filler wire for Al/SiC-MMCs