Process And Properties Of Large Sized Aluminum Foam Sandwich Panels Prepared By Powder Metallurgy Method

The aluminum foam sandwich panels have the characteristics of light weight,high energy absorption capability,excellent electromagnetic shielding and so on.At the same time,the"sandwich" structure makes the specific strength and specific stiffness of the materials significantly improved than that of single foam aluminum.It is a kind of advanced structural and functional integrated materials with broad application prospects in aerospace,automobile manufacturing,national defense and military industries.This thesis is financed by the key R&D project of Liaoning Province,which is supported by the large-scale foam aluminum sandwich structure material controllable preparation and typical component research and development(No.2019JH2/10100008).In this paper,the preparation technology of large-scale aluminum foam sandwich panels made by rolling composite powder metallurgy method is studied,and the electromagnetic shielding performance and mechanical properties of the products are characterized and analyzed.It is expected to provide experimental basis and theoretical basis for the design and development of material application components.The main work and research results are as follows.With 3003 aluminum alloy as the panel,Al,Si,Mg and Cu powder as the matrix raw material,and TiH2 as the foaming agent,the foam with a good core layer was successfully prepared through mixing,cold rolling,hot rolling,foaming and other processes.Aluminum foam sandwich panel with structural and plate core interface strength.Rolled composite pilot tests of 350 mm×2000 mm foamed preforms were performed at Chinalco Group Northeast Light Alloy Co.,Ltd.The optimized preparation processes of the foamed aluminum sandwich panel determined in the study are as follows:In the cold-rolling compounding stage,a multi-pass rolling scheme with a small reduction of 1 mm per pass is adopted,which can effectively reduce the loss of powder while eliminating the residual air in the powder,and the densification effect is good.In the hot rolling stage,the rolling speed of 10 m/min can effectively control the wide deformation of the rolled product.The suitable rolling temperature range is 240? to 400?.If the rolling temperature is too low,cracks in the core powder after rolling may occur.If the temperature is too high,TiH2 will decompose in advance.By exploring the pass reduction ratios at different hot rolling temperatures,it is found that the critical reduction ratio of the composite is 25%,and when the reduction ratio is higher than 35%,the stress effect easily causes the edge of the sheet to crack.In the foaming stage,the factors that affect the foaming effect of the preform include heat transfer speed,foaming temperature and foaming time.After taking measures to accelerate heat transfer,the uniformity of core porosity is significantly improved,and the expansion ratio can be greatly increased from 4?5 times to 8?9 times.By adjusting the foaming process at the foaming temperature of 600?630? and the foaming time of 12?21 min,the core aluminum foam with porosity of 90.6%and average pore diameter of 3.6 mm can be obtained.The shielding effect of aluminum foam sandwich panels on electromagnetic waves is reflected in three aspects:reflection loss,absorption loss and multiple reflection loss.The shielding effectiveness of aluminum foam sandwich panels in the UHF section of 2.6?8.2 GHz is fluctuating with frequency,and the value is distributed between 10?50 dB.The compressive stress-strain curves of aluminum foam sandwich panels prepared in this study can be divided into three stages:elastic deformation stage,stress platform stage and compaction stage.The continuous brittle fracture of the core layer occurs in the stress plateau stage.Elastic deformation and brittle fracture are the forms of energy when aluminum foam core is compressed.The compression stress strain curve of the aluminum foam sandwich panel reaches the peak value of 8 MPa,the elastic gradient reaches 0.45 GPa,the platform stress reaches 6.2 MPa,and the absorption energy reaches 4 MJ/m3.The deformation of aluminum foam sandwich panels under bending load is divided into three stages:elastic deformation stage,yielding stage and complete failure stage.The yield stage is the main energy absorption stage,and the failure mode is the sag at the loading point,the overall instability and the delamination of the core.Under the span of 100 mm,the foam aluminum sandwich panel with a porosity of 87.13%?90.91%can withstand the load of 0.8?2.5 kN.The lower porosity,the better flexural performance.