Preparation And Mechanical Properties Of Ti/Aluminum Foam/Ti Composite Sandwich Structures

Aluminum foam is a new type of ultra-light porous material which is composed of pores and scaffolds.Many excellent characteristics make it show a broad application prospect in the vigorous development of modern industry,and has been applied in daily life.However,the low absolute strength of aluminum foam,poor mechanical properties,poor surface smoothness,corrosion and other problems seriously limit its application in industry.In view of the existing problems of Aluminum foam,the research on aluminum foam is gradually extended from the study of aluminum foam preparation technology to the study of improving and optimizing the preparation and mechanical properties of Aluminum foam composite structures（AFCSs）.As a typical composite structure in AFCSs,Aluminum foam sandwich（AFS）significantly improves the specific strength and stiffness of this kind of material,which has a better application prospect than single aluminum foam.Therefore,in this paper,the preparation process of AFS material was studied in terms of pore morphology and binding strength,and the mechanical properties of prepared samples were characterized and analyzed,providing experimental data and theoretical basis for its application in industry and the design and development of aluminum foam application components.Firstly,the preparation technology of AFS was studied based on melt foaming method.The Transient liquid phase bonding method-Aluminum foam sandwich（TLP-AFS）was prepared.By optimizing the preparation process,the uniformity of TLP-AFS pore structure was improved,and the metallurgical bonding between the panel and the core layer was realized.TLP-AFS three-point bending test results show that the load curve presents three stages:elastic deformation stage,crack growth stage and platform stage.The bending strength increases with the increase of density.When the bending degree is 15 mm,The energy absorption capacity(W_EA=13.48 J)and specific energy absorption capacity(W_SEA=0.58 J/g)of TLP-AFS at 0.80 g/cm³ density were 3.59 times and 3.22 times of those of samples with 0.69 g/cm³ density(W_EA=3.76 J,W_SEA=0.18 J/g).Failure modes include compaction deformation of aluminum foam core layer and shear and cracking of core material as well as bending deformation and peeling failure of TA2 panel.The combined action of different stresses at different locations of samples results in multiple failure modes of TLP-AFS materials.Secondly,Powder metallurgy technology was used to successfully prepare Powder metallurgy technology-Aluminum foam sandwich（PM-AFS）based on powder metallurgy joint forming,achieving a good combination of panel and core foam structure.The experimental results show that the uniform distribution of Ti H₂ in Al powder can be achieved by prolonging the mixing time of Al particles and Ti H₂.No macroscopic gap was observed between the prefabricated surface plate and the core layer when the hot pressing temperature was 430℃,the hot pressing pressure was 300 MPa and the heat preservation was 60 min.The PM-AFS samples after foaming produce good metallurgical bonding,and the elements at the bonding layer mainly exist in the form of binary phase Al₃Ti intermetallic compounds.The shear test shows that when the hot pressing temperature is 430℃and the hot pressing pressure increases from 100 MPa to 300 MPa,the bond strength of the prefabricated body increases by 122.8%,and the bond strength of the prefabricated body is 3.49～8.75 times of the shear strength of ordinary aluminum foam core.The failure mode of PM-AFS sample is mainly aluminum foam core failure.It indicated that PM-AFS prepared under these parameters could achieve better binding conditions.The results are of particular importance for the application of PM-AFS materials requiring strong connections.Thirdly,in order to verify the mechanical properties of PM-AFS under quasi-static conditions,axial compression and three-point bending tests were conducted on PM-AFS materials.In the process of compression,the existence of the panel plays a supporting role,which makes the material yield under greater stress,showing a significant increase in compressive load,so that the PM-AFS material has a higher axial bearing capacity.In the three-point bending process,the bending curve has a long platform area due to the presence of the panel,and with the increase of the thickness and density of PM-AFS,its bearing capacity and energy absorption capacity increase.PM-AFS bending failure modes mainly include compaction,dislocation movement of aluminum foam core layer,indentation and other failure modes.Compared with TLP-AFS,PM-AFS has better bonding strength without panel peeling phenomenon.Finally,in order to further verify the dynamic impact bearing performance of PM-AFS,American Instron-9350 was used to carry out drop weight impact test on PM-AFS.The test results show that the samples with different thickness have little effect on the impact bearing performance under the same impact energy,but the height of the aluminum foam core layer can affect the load-displacement distance.For the penetration,the PM-AFS samples with higher thickness show better energy absorption capacity.The main reason is that the panel acts as the main bearing member,while the energy absorption of the PM-AFS structure is mainly generated when the aluminum foam core layer is impacted.The results are verified by continuous impact.PM-AFS have strong impact resistance and residual impact resistance to repeated shocks.In view of its good energy absorption and residual impact resistance,PM-AFS has great advantages in protection and shock prevention.