Research On Process And Property Of Plasma Arc Welding Of SiCp/6061Al Composites

SiCp/Al metal matrix composites (SiCp/Al MMC_S) are wildly applied in aerospace, automobile and electron industry owing to their excellent properties, including high specific strength, specific stiffness and specific modulus, attractive dimension stability and vibration resistance, high temperature resistance, corrosion resistance and radiation resistance, etc. However, on account of much difference in the heat physical and chemical performance of reinforcement and matrix, and due to the possible formation of brittle reaction product, Al₄C₃, by interfacial reaction in high temperature, it is hardly to form high-quality welding joint, and reduces the mechanical property of weld greatly, which is confining the development of SiC_P/Al composites. So the key problem is avoiding or decreasing the formation of brittle product.In this paper, the weldability of SiC_P/Al composites was studied by the technology of plasma arc welding through SiCp/6061AlMMCs. The composites was welded in the way that titanium and mixed powders were used as alloying filler metal and N₂ and Ar were used as the plasma gas. The influence of different alloy metals on weld organization and performance were systematically investigated by tensile and microhardness tests, OM, SEM, EDS and XRD analysis.The results showed that interface reaction was effectively controlled with titanium as the filler metal and the new reinforcing phases were generated, the microstructure of welding line was dense and the tensile strength obtained 50.89% of basic metal, the microhardness reached maximum in the middle of welding line.The filler metals all could reform wetting property of Al to SiC in order to form well-knit interface while Ti-Si,Ti-Mg and Ti-Cu mixed powders were employed as filler metals to PAW SiCp/Al MMC_S. The effect indicated that the preferable tensile strength achieved 232.2Mpa and 204.7Mpa respectively when Ti-Si and Ti-Mg mixed powders put into weld crater, and the fracture present gliding fracture character; however, the tensile strength only achieved 187.5MPa because of the formation of needle-like harmful phase Al₄C₃ and Al₂Cu, and the fracture was visible rock-candy structure. The tensile strength changed distinctly when different welding current, welding velocity and plasma gas match were adopted in welding. The technologic parameters to achieve high performance joint were that welding current was 120A, welding velocity was 140mm/min and the nitrogen volume content was 15%.The high quality welding joint was attained easily on account of alloy filler metals, which improved the solidification and crystallization velocity of molten pool, reformed improve wetting property of basic metal to reinforcing phase, made reinforcing phase particles distributing equably in welding line and reduce the tendency of granules.