Study On The Preparation Method And Mechanism Of Aluminum Foam Sandwich With Complex Surface

Aluminum foamsandwich is three layers structure,which is composed of face plate and aluminumfoam coreplate.It has advantages of compactmetal and metalicfoam,which has a broad application prospect in the fields of aviation,space and automobile.At present,the main preparation methods of the sandwich are adhesive bonding method and powder compact meltingmethod.The adhesive bonding method is poor in environmental adaptability,and the process of powder compact meltingmethod is complex,and aluminumfoamsandwichis the main plate structure.In order to further expand the application of aluminum foam sandwich,it is of great engineering value to study the preparation method of sandwich with complex surface.In this paper,in view of the existing problems in the manufacturing and application of aluminum foam sandwich,a new preparation method of aluminum foam sandwich with complex surface is developed,which is the process route ofpowder pack rolling + hot forming,and the high temperature foaming.By means of theoretical analysis,experimental research and numerical simulation,the key technology and related mechanism in the process are studied systematically.There is no obvious change in the morphology of the titanium hydride particles after the oxidationtreatment.The oxide films of Ti3O and TiO2 are formed in turn from inside to outside.and the titanium hydride particles with the different proportions of Ti3O/TiO2will show different colors.With the increasing of oxidation temperature and time,the mass loss rate of titanium hydride decreases and the thermal decompositiontemperature increases significantly.The mass loss rate of titanium hydride is only 0.59%after the oxidation treatmentat 520?/3h,while the thermal decomposition temperature reaches 624?,and increases by 97?.In this paper,titanium hydride has been oxidized at 480?/1hin order to prepare AlSi12 alloy foamsandwich.The relative density of core plate is symmetrical along the middle line.The relative density of core plate increases with the increasing of rolling reduction,and the plateau region of relative densityincreases correspondingly.When the rolling reduction is more than 80%.the relative density and its distribution are almost constant.On this condition,the relative density reaches 0.98,and the effective utilization of sandwich precursorreaches 70%.The 5 ?m diffusion layer has formed between the face plate and core plate,and the interface of the face plate/core plate has realized the metallurgical bonding.The foaming process of sandwich precursor is composed of three stages:pore formation,growth and fracture.At different stages,the microstructure of pore wall is different.The microstructure of pore wall transforms from spherical solid solution? + eutectic phase to dendritic solid solutiona+ eutectic phase.The rolling reduction,foaming temperature and foaming time have an interactive effect on foaming behaviors of sandwich precursor.The larger the rolling reduction and the higher the foaming temperature,the higher the expansion factor of sandwich precursor after the foaming.The foaming time has the optimum value.The optimum foaming time is 180s at the foaming temperature of 740?.and the expansion factor of sandwich precursorreaches 2.56.The elastic modulus and yield strength of aluminum foam sandwich are lower than the theoretical value of Gibson and Ashby model,which are close to the mechanical properties of open-pore aluminum foam,and the deformation propertiesare controlled by the bending of pore edge.The energy absorption efficiency of aluminumfoamsandwich has plateau region,and the higher the relative density and the shorter the plateau region.The absorption energy of the sandwich increases first with the increasing of the relative densityand then decreases.At the relative density of 0.34,the energy absorption reaches the maximum value of 1.41MJ/m3.Aluminum foamsandwich has three failure modes:face yield,indentation and core shear.Based on this,the relationship curve between the mass index and the load indexof the sandwich is established.For a given load index,the structure mass index can be calculated according to the curve.The sandwich precursor is both temperature sensitive material and rate sensitive material.Under the high temperature and low strain rate,the sandwich precursor has better forming ability.Under the condition of 450?/0.001s-1.the peak flow stress and elongation are 22.1 MPa and 23.8%respectively.During deformation,the face plate and core plate can be effectively deformed simultaneously,and the fractured TiH2 powder is the crack initiation.Aluminum foamsandwiches with curved surface and complex surface are prepared on the basis of the process:hotformingat 450?+ foaming at 780?/210s.The feasibility of the process is verified,and the potential application is demonstrated.