| SiC particle reinforced aluminum metal matrix composites(SiCp/Al MMCs), which exhibit excellent combinations of high specific strength, high specific stiffness, low coefficient of thermal expansion and excellent wear resistance, have more and more widely application in aerospace-flight, aviation structure, and heat resistant wearable parts of engine. However, Aluminum metal matrix composites is not applied widely in industry duo to its poor weldability. The welding technique is the key to wide industry applicaton for Aluminum metal matrix composites.The effects on microstructures and mechanical properties and the alloying mechanism of weld by plasma arc "in-situ" welding (Ar and N2 as ionized gas, Ar as fielded gas) of SiCp/6061Al MMCs filling with flux-cored wires were investgated with the help of OM (optics microscopy), SEM (scanning microscopy), TEM (Transmission electron microscopy), EDS (Energy Disperse Spectroscopy) and XRD (X-ray diffraction) in the present work. A systemic analysis was also carried out on the formation mechanism and refinement technology of the long strip Al3Ti phase.Based on the analysis of the role of Ti in the weld, which can inhibit the harmaful phase and inprove the performance of the weld. The rich-Ti flux-cored wire was produced specialized for welding of SiCp/Al MMCs, which have the advantage of simply producting process and easily adjusting ratio of the powder.Three kind of flux-cored wires were used for the SiCp/Al MMCs welding test, that is Ti-Si-Al, Ti-Mg-Al and Ti-Si-Mg-Al wires. The content of Ti in the Ti-Si-Al and Ti-Mg-Al flux-cored wires is unchanged all the time, so that the role of Si and Mg in the motlen pool can be analyzed by changing the ratio of them repectively in the flux-core wires during welding. The Ti-Si-Mg-Al flux-cored wire was prepared on the base of the research of Si and Mg. The test results show that the highest tensile strength of the weld joints was getting by plasma arc welding of SiCp/Al MMCs with 15Ti-5Si-5Mg-Al flux-cored wire as filler and the maximum value of the joint is 267 MPa up to 83.4% of the base metal.As the formation of long strip Al3Ti phase, the tensile strength of the joint will decreased when too much Ti fusing into the pool, although the need like brittle phase Al4C3 is inhibited. Combined the observation of microstructure with the molding mechanism of Al3Ti particles, we can get the conclusion that the long strip Al3Ti phase in the weld is an aggregates, which is consist of fine Al3Ti particles. The tensile strength of the weld can be improved by suppressing the formation of the long strip Al3Ti phase, while the formation of the long strip Al3Ti phase can be inhibited by increasing the movement of the molten pool or improving the ratio of the alloy elements in the flux-cored wires. |
