Research On Sound Eliminating Performances And Energy Absorption Properties Of Porous Aluminum Alloys By Laser Additive Manufacturing

Closed-cell porous metal material is a new type of functional material,which has been attracted a wide attention due to its good energy absorption properties,sound insulation properties and sound absorption properties.The manufacture of porous aluminum alloys by laser additive manufacturing technology can not only solve its problem of tight junctions,but also can achieve the manufacture of large porous acoustic enclosures and the porous vibration reduction parts of key components of complex structures.Therefore,it is of great significance to carry out research on the laser additive manufacturing of porous aluminum alloys.In this paper,a new type of laser additive manufacturing process for porous aluminum alloys is developed.The pre-treated modified pore-forming agents were fed into the molten pool in a synchronized powder feed mode to prolong the incubation period of the pore-forming agents and eventually achieve porous structures.Energy absorption performance,sound insulation performance and sound absorption performance of porous aluminum alloys were characterized and evaluated.At the same time,the influencing rules of the powder pretreatment process,Ti addition and the addition of rare earth La2O3 were investigated.In addition,a kind of porous phononic crystal structure has also been designed.Through the combination of simulation and experiment,the variation law of the acoustical performance is explored,which provides a theoretical basis for its practical application.The results show that the best parameter of electroless plating of powders is 30min for primary plating.The optimum parameters of laser direct deposition are as follows:the laser power density is 57.20W/mm²,the scanning rate is 6mm/s,the multichannel overlap rate is42%,the multilayer hole-making layer thickness is 0.7mm,and the scanning path is a one-way long grating scan path.In the whole frequency domain,the sound insulation performance of the porous aluminum alloy is proportional to the porosity,but is inversely proportional to the size of pores,while the porosity is the main control effect when the frequency is low;the ideal energy absorption efficiency reaches 0.58 within the energy absorption range,and the average sound insulation amount reaches 40.74dBAt the same time,the study found that the method of rehydration can improve the powder pretreatment process,thereby significantly improving the energy absorption properties and sound insulation of porous aluminum alloys;the addition of Ti reduced the porosity and the average pore size,but improved the elastic modulus and yield strength.As a result,the energy absorption efficiency increased first and then decreased,while the sound insulation performance was always improved.The addition of rare earth La₂O₃ increased the areal density.The addition of 0.5%La₂O₃ increased both the energy absorption efficiency and the sound insulation performance.The addition of 1%La₂O₃ increased the energy absorption efficiency,but the sound insulation performance was greatly reduced.The ABAQUS finite element analysis results and the experimental results of the laser-selected porous phononic crystal sample showed that the acoustic waves incident inside the porous phononic crystal structure undergoes scattering reactions after contacting the diffuser structure,and the same-phase scattering waves interfere with each other,resulting in Some of the sound energy is converted into heat energy,which in turn provides sound insulation and sound absorption effects.Due to the presence of microscopic pores in the sample formed by the laser selective zone,the sound insulation in the low frequency range is in agreement with the calculated value,and the sound insulation performance in the high frequency range is slightly higher than the calculated value.