Study On Ultrasonic Welding Preparation Of Bulk Metallic Glass Fe₇₈Si₉B₁₃

Bulk metallic glass (BMG) is an engineering structure material with widelypotential applications. In order to realize the connection of amorphous alloy,exploring efficient energy-saving metallurgical combination technology hasimportant research value. Some studies have reported that the friction welding, pulsewelding, electron beam welding, laser welding and explosion welding technologycould be used to fabricate bulk metallic glass.Firstly, this paper carried out the solid connection of multilayer Fe78Si9B13sheetsbased on the ultrasonic welding technology, and achieved good welding joints andappropriate welding process parameters. The welding joints were studied bymicrostructure observation (OM and SEM), micro-X-ray diffraction analysis(micro-XRD), differential scanning calorimetry analysis (DSC), microhardness testand welding temperature test. The connection mechanism of the ultrasonic weldingand crystallization for multilayer Fe78Si9B13sheets were analyzed, which provides aneffective way for the preparation of bulk metallic glass.Results show that, two to six layer sheets can be connected together byultrasonic consolidation due to the superplasticity and high heat stability ofsupercooled liquid amorphous Fe78Si9B13. The appropriate process parameters ofultrasonic welding for two layer sheets are that, ultrasonic time is0.20s and staticpressure is1.37×103N. The appropriate process parameters of ultrasonic welding forthree to five layer sheets are that,(1) ultrasonic time is0.19s and static pressure is1.72×103N,(2) ultrasonic time is0.20s and static pressure is1.60×103N,(3)ultrasonic time is0.21s and static pressure is1.49×103N,(4) ultrasonic time is0.22sand static pressure is1.37×103N. The appropriate process parameters of ultrasonicwelding for six sheets are that, ultrasonic time is0.22s and static pressure is1.60×103N. Although the point gap area of joint interface cannot be effectivelyconnected, the solid combination of contact area can be realized without defect andcrystallization, which keeps the original thermal resistance. The joint hardness ofweld zone and heat affected zone both increased slightly. The interpass temperature of sheets was in supercooled liquid temperature range of amorphous Fe78Si9B13.Secondly, ultrasonic welding of multilayer Fe78Si9B13sheets was simulated byusing the finite element analysis software ANSYS. The two-dimensionalaxisymmetric heat source model was established. The transient temperaturedistribution in the welding process was obtained. Results show that, the highesttemperature of joint interface (536°C) is greater than the crystal transitiontemperature of495°C for two layer sheets under the ultrasonic time0.22s and staticpressure1.37×103N. For three to five layer sheets, the highest temperatures ofinterface which are respectively485°C,462°C and442°C, are all in the supercooledliquid region. For six layer sheets, the maximum temperature of interface (409°C) isbelow the glass transition temperature of420°C. This demonstrates that multilayeramorphous sheets after ultrasonic connection with appropriate process parameters canavoid crystallization.Finally, ultrasonic welding of Fe78Si9B13sheet and3003aluminum was carriedout. Various test results show that, a clear weld without negative phenomenon wasobserved in the joint interface of Fe78Si9B13and3003Al, and the amorphous areakeeps amorphous and the hardness of weld zone reaches to6×102kg/mm2and thetensile peel strength of joint is about9.81×102N/m. The appropriate processparameters are that ultrasonic time is0.14s and static pressure is1.37×103N, andultrasonic time is0.15s and static pressure is1.14×103N. In addition，the plastic flowof amorphous alloy and aluminium is an important factor to complete solidcombination.