Research On The Technology Of Ultrasonic Pulse-frequency Plasma Arc "In-situ" Welding Of SiCp/6061Al MMCs

Aluminum metal matrix composites are more and more widely applied in aerospace,spaceflight,auto manufacturing due to their excellent combination properties of high specific strength,high specific stiffness,high elastic modulus, better wear-resistance.But Aluminum metal matrix composites is not applied widely in industry because of its poor welding ability.The welding technique is the key to expand its industry application for Aluminum metal matrix composites.Therefore,we propose a new method named ultrasonic frequency pulse "in-situ" plasma arc welding to make an exploration for the application of SiCp/6061Al MMCs.Combining low-power ultrasonic frequency pulse power and plasma welding,we set up a ultrasonic frequency pulse arc welding system,so that the plasma arc welding is modulated by high frequency to be a kind of controllable ultrasound emission source at the same time as a welding heat source.The effects of this welding process on microstructures and mechanical properties(Ar and N₂ as ionized gas,Ar as fielded gas) of SiCp/6061Al MMCs and mechanism of its alloying process is investigated in the present work.The changes of microstructure and composition of fusion welded joints of composites was in observation with OM(optics microscopy),SEM(scanning microscopy) and XRD(X-ray diffraction).And mechanical properties of fusion welded joints were measured by microhardness and tensile tests.The experimental results show that the same frequency arc-ultrasonic could be excited.The formation of Al₄C₃ was effectively prohibited and the new weld reinforced such as Al₃Ti,TiC,TiN was produced.Compared with not modulated,the arc-ultrasonic could significantly reduce the size of the reinforced and also improve its distribution to make the welding joints denser.The hardness of the weld middle zone had become lower and the strength of welding joints had been increased, reaching 240MPa.Observing the distribution of the reinforce on different exciting frequency,we found the distribution become more uniform.Especially in the resonant interval 40KHz,50KHz,the distribution was better and the strength of welding joints was bigger.And the strength reached 263MPa at 40KHz.