Study On Ultrasonic Assisted Laser Welding Process And Mechanism Of SiC_p/6061 Aluminum Matrix Composite

SiC particle reinforced aluminum matrix composites have the advantages of low density,low thermal expansion coefficient,high specific strength,good wear resistance and corrosion resistance,etc.,and have extremely broad application prospects in the fields of shipbuilding,aerospace and automobile manufacturing.However,due to the great difference in physical and chemical properties between SiC and Al matrix,it is difficult to weld SiC/Al material.Especially during fusion welding,the interface reaction will occur in the weld,resulting in the formation of acicular brittle phase Al₄C₃,which results in the serious decline of mechanical properties of the joint,restricting the further application and development of SiC/Al material.In this paper,the pulse and continuous laser waveforms are used respectively,and the 17%volume fraction of SiC_P/6061 is used as the research object for welding experiments.The influence of various process parameters on the weld formation is systematically discussed;supplemented by adding an intermediate layer and applying means such as ultrasonic vibration are designed to reduce and eliminate pores,improve the distribution of phases in the weld,and improve the mechanical properties of the laser welded joints of aluminum-based composites.First,a continuous laser self-fusion welding test was carried out on SiC_P/6061,and the influence of various welding parameters on the quality of weld formation was explored through the single control variable method.The results show that under the selected parameters,the SiC particles in the weld will dissolve and react with the Al matrix at high temperature to form the needle-like brittle phase Al₄C₃.The size of Al₄C₃grows as the heat input increases.When the welding heat input is too large,a large number of macroscopic pores appear in the welding heat-affected zone.In order to solve the problem of brittle phases in the weld,Ti foils of different thicknesses were selected as the filler material.The results show that the Ti foil filled can improve the fluidity of the molten pool,inhibit the interfacial reaction and generate TiC particles that are more compatible with Al.Different content of Ti element will have different effects on the structure of the weld.Ti content is small（t Ti≤0.03mm）,the metallurgical products in the weld are TiC particles and Al₄C₃brittle phase;if Ti content is excessive（t Ti>0.03mm）,TiC particles and fishbone-like Al₃Ti will be formed in the weld,which is too long Large Al₃Ti will be detrimental to the mechanical properties of the joint.At this time,the maximum tensile strength of the welded joint is 280MPa,which is about 78.6%of the strength of the base material.Using pulsed laser for self-fusion welding of SiC/Al materials,under the condition of ensuring penetration,compared with continuous laser welding,the brittle phase size in the weld is reduced,but a large number of them are still present in the weld.After the Ti foil is filled,the tensile strength of the joint is not significantly improved,and the weld structure appears delamination.The maximum tensile strength of the welded joint is 120MPa,which is only 33.7%of the strength of the base metal.In order to reduce the segregation of the reinforcing phase and reduce the porosity of the joints,an ultrasonic-assisted laser welding platform was built to introduce ultrasound into the molten pool,and use the acoustic flow and cavitation effects of the ultrasound on the molten pool to stir the molten pool and refine the crystals.The purpose of the grain.The results found that 30%amplitude ultrasound can better eliminate the pores in the joint and refine the tissue.When the laser power is 2000W,the welding speed is 0.02m/s,0.1mm Ti foil is added,and 30%amplitude ultrasound is applied,the weld is beautifully formed without defects,and the joint strength is 298MPa,which is 6%higher than that without ultrasound.It is 83.7%of the strength of the base metal.