At present, aluminum metal matrix composites (Al MMCs) are more and more widely applied in aerospace, spaceflight, auto manufacturing, optical instrument and sports industry due to their excellent combination properties of high specific strength, high specific stiffness, high elastic modulus, better wear-resistance and high temperature resistance.
But Al MMCs are not applied widely in industry due to their poor weldability. And the welding technique is the key to wide industry application for Al MMCs . SiCp/Al MMCs have been extensively investigated worldwide. Many methods such as brazing, diffusion bonding, transient liquid phase bonding, gas shielded arc welding and laser welding have been used to weld these materials. And fusion welding is the most flexible and versatile one. The previous investigations show that how to prevent the formation of harmful phase Al4C3 is the key for the fusion welding of SiCp/Al MMCs. The defects, such as pores, microfissure and inhomogeneous wild phase would debase the mechanical properties joints, which should be avoided in the welding process. In our previous investigation, pure titanium sheet was filled into the molten pool during argon-nitrogen mixture gas plasma arc welding of SiCp/Al MMCs in order to obtain a particle reinforced composite weld. And the formation of needle-like brittle phases Al4C3 is
prevented completely because titanium and carbide formed TiC preferably. But the mechanical properties are debased by some defects, such as pores, cracks and incomplete fusion of titanium owing to the high welding current demanded by the high fusion point of titanium and poor fluidity of molten pool.
Both technics and metallurgy should be taken into consideration in order to improve the weldability of SiCp/Al MMCs. Decreasing heat input of molten pool is the main approach in technics. But in order to ensure fusion penetration, there is a limitation of reducing the heat input. And some elements that could improve the fluidity of molten pool and inhibit the interface reaction are added into the weld in metallurgy. To improve the structure of weld and performance of welded joint in plasma arc in-situ welding of SiCp/Al MMCs, Ti-Al was filled into the molten pool and its effects on
microstructures and mechanical properties of weld were investigated in the present work
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