Effect Of Alloying Filler Titanium And Other Welding Parameters On Microstructure And Mechanical Properties Of Welded Joint During PAW Of SiCp/6061Al

SiC particle reinforced aluminum metal matrix composites(SiCp/Al MMCs) are widely applied in aerospace, transportation and electronic industries due to their excellent combinations of high specific strength, high specific stiffness, low coefficient of thermal expansion and excellent wear resistance, Development of reliable and economic joining techniques is of significant importance for the successful commercialization of SiCp/Al MMCs, because joining to other components made of similar composites and other structural metallic materials is often necessary when practically applied as structural components in mechanical systems or structures. However, due to the severe heterogeneity of the material constitution and the great difference in both physical and chemical properties between the reinforcing SiC particles and the aluminum alloy matrix, joining of SiCp/Al MMCs especially when made of powder metallurgical routes has been remaining as a difficult challenging technological problem. The most serious problems are the dissolution of SiC particles and subsequent formation of the needle-like detrimental phases of Al₄C₃ during fusion-welding process. The formation of the needle-like aluminum carbides is very deleterious to the mechanical properties of the weld because the very brittle aluminum carbide in needle-like morphologies greatly deteriorates the ductility and reduces fracture toughness. Moreover, the aluminum carbide is susceptible even to moisture corrosion, greatly reducing the corrosion resistance of the weld. It is still almost impossible to completely prevent the decomposition of SiC reinforcements and the subsequent formation of the detrimental Al₄C₃ phases during fusion-welding even if the processing parameters was carefully optimized. Therefore, preventing the formation of the harmful aluminum carbides during fusion-welding process is of crucial importance for successful welding of SiCp/Al MMCs.'In-situ' weld-alloying/plasma arc welding with Ar and N₂ as ionized gas, Ar as fielded gas, and titanium as the alloying element is utilized to join a SiCp/6061Al MMC in order to prevent the formation of the needle-like harmful Al₄C₃ phases in the weld. Microstructure of the weld is characterized by XRD,OM,SEM and EDS as functions of alloying element content and plasma arc welding processing parameters. Microhardness and tensile properties of the weld are evaluated. Results show that the...