Effect Of Surface Treatment And Structure On Cushioning And Energy Absorption Properties Of Aluminum Foam

Aluminum foam is a kind of material with specific function and structure,which has the characteristics of light weight,high specific strength,energy absorption and shock absorption.It is widely used in aerospace,automobile industry,transportation and other industries.In recent years,the rapid development of these industries has put forward higher requirements for the buffer energy absorption performance of aluminum foam.The strengthening method of surface treatment not only improves the cushioning energy absorption performance of aluminum foam,but also improves the other functional properties of the material,and thus it has received more attentions.In this paper,three representative coatings of Al₂O₃ coating,Ni-W coating and Cu coating on the surface of closed-cell aluminum foam were prepared by anodizing and electrodeposition,and the mechanical tests were carried out.Based on several buffering energy absorption evaluation indexes,the buffering energy absorption evaluation of surface treated aluminum foam was carried out,and combined with SEM and other analysis and characterization methods,the effects of coating material and ductility on the mechanical properties,deformation and energy absorption properties of aluminum foam were studied systematically.In addition,through the drop weight experiment,combined with high-speed photography and ARAMIS system,the dynamic impact tests of three kinds of prefabricated chamfered samples were carried out to explore the feasibility of optimizing the peak impact stress by improving the macro-structure of aluminum foam.The main results are as follows:(1)Anodizing treatment can effectively improve the buffer energy absorption characteristics of aluminum foam,and with the increase of oxide thickness,the performance improvement is more significant.The brittle deformation mode of the outer cell dominates the overall deformation law of the material,which leads to the increase of the length of the platform zone,which is the main reason for the improvement of the buffer energy absorption performance of anodized aluminum foam.(2)Similar to the Al₂O₃ ceramic coating,the electrodeposited metal coating shows the same brittleness characteristics in the stress-strain curve,which also has a positive effect on the length of the aluminum foam platform zone.Compared with Al₂O₃ coating,the load carrying capacity of metal coating on aluminum foam is higher than that of anodized aluminum foam,and the effective energy absorption value of anodized aluminum foam increases more significantly,but the mass specific energy absorption decreases obviously.(3)Annealing treatment improves the ductility of copper coating.After annealing,the cell deformation mode of the sample surface changes from brittle fracture before annealing to ductile deformation mode dominated by cell buckling,and the length of the platform zone is basically the same as that of pure aluminum foam.Due to the brittle deformation characteristics of the unannealed samples,the length of the platform zone is 9.09%higher than that of the annealed samples,and the effective energy absorption value is 25.66%higher.(4)The polarization curves of each sample were obtained by electrochemical test,and the effects of all kinds of coatings on the corrosion resistance of aluminum foam were studied.all kinds of coatings improved the corrosion resistance of aluminum foam and reduced the tendency of corrosion.Among them,the corrosion resistance of aluminum foam treated by anodization is the best.(5)The prefabricated chamfer changes the initial deformation mode of the foam and effectively reduces the initial peak load of the aluminum foam in the dynamic impact process.The type of chamfer determines the trend of the platform area and the overall deformation mode of the material.The research results of this paper show that after the surface treatment of closed-cell aluminum foam by anodizing and electrodeposition,the improvement of energy absorption of closed-cell aluminum foam is the result of the improvement of load-bearing capacity and the growth of platform area.Among them,the growth of the platform area is the main reason for the improvement of the energy absorption efficiency of aluminum foam,which increases the proportion of the effective energy absorption area of aluminum foam and is closer to the ideal energy absorption material.At the same time,prefabricated chamfer can weaken the impact peak load.as an economical and feasible means,this method provides a new idea for the controllable design of dynamic mechanics of aluminum foam.