Experimental And Numerical Research On Laser High-speed Impact Welding Of Brass And Dissimilar Metals

Laser high-speed impact welding as the solid phase welding technology is particularly suitable for the connection of dissimilar metals with microscopic scales,which provides a new way for micro-welding of brass and dissimilar metals.In this paper,the laser high-speed impact welding technology was used to realize the micro-welding of brass and dissimilar metals.The microstructure and mechanical properties of laser high-speed impact welding samples and the formation mechanism of interfacial wave were systematically investigated through experiment study and numerical simulation.The main research contents and results are as following:Firstly,the welding of Al/Brass was realized by laser high-speed impact welding process.In this experiment,the surface and cross-sectional morphology of the welding samples were observed by optical microscopy(OM).The welding interface microstructure was observed and analyzed by scanning electron microscopy(SEM)and X-ray energy spectrometer(EDS).The mechanical properties and failure modes of welding joints under different laser pulse energies were studied by tensile shear test and peeling test.The results showed that the laser pulse energy has a significant influence on the interface morphology,and the wavelength and amplitude of the interface wave increase with the laser pulse energy.When the laser pulse energy was higher than 1200 mJ,the local melting blocks would be formed in the valley region on the brass side.EDS analysis showed that slight element diffusion occurred at the welding interface.With the increase of laser pulse energy,the maximum tensile force and peeling force increased.It was considered that the increase of interfacial wave size was beneficial to the improvement of welding joint quality.However,the increase rate of tensile force and peeling force gradually decreased with laser pulse energy,which indicated that the occurrence of local melting adversely affected the welding joints.In addition,two failure modes occurred in the tensile shear test and peeling test,which were spalling failure and fracture failure.Secondly,the experimental study on Brass/SS304 by laser high-speed impact welding was carried out.The effects of different laser pulse energies and flyer plate thicknesses on the surface morphology and microstructure of welding joints were studied.The mechanical properties of welding joints were systematically studied by combining the local thinning phenomenon of flyer plate.The results showed that when the thickness of the flyer plate was constant,the wavelength and amplitude of the interface wave increased with the laser pulse energy.Under the same laser pulse energy,the wavelength and amplitude of the interface wave decreased with the increase of the flyer plate thickness.EDS analysis showed that the thickness of the element diffusion layer was about 6μm at the bonding interface.The spalling failure and fracture failure occurred in the tensile shear test and peeling test.Under the excessive laser pulse energy or standoff distance,the maximum tensile force and peeling force decreased sharply.In addition,the maximum tensile force and peeling force increased with the increase of the flyer plate thickness.Finally,the Al/Brass and Brass/SS304 welding combinations were simulated by SPH method.The dynamic response of high-speed impact welding and the formation mechanism of interface wave were explored.The simulation results showed that the amount and velocity of jet increased with the increasing impact velocity and the jet mainly came from the material with lower density.The impact velocity was an important factor affecting the interface waveform.With the increase of initial impact velocity,the wavelength and amplitude of the interface wave increased.Under the combined effect of shear stress and impact pressure,the interfacial wave was formed by the material with lower density periodically penetrate another material.In the Al/Brass simulation combination,when the impact speed was set at 1200m/s,the most serious plastic deformation occurred in the valley region near the brass side,resulting in a sharp rise in temperature.The region with the highest temperature in the simulation coincided with the local melting region in the experiment.The research laid a foundation for the laser high-speed impact welding process applied to the micro-welding of brass and dissimilar metals.