Study on Preparation and Properties of Aluminum Foam Sandwich by Mixing Elemental Powder Rolling
|Keywords||aluminum foam sandwich pore structure powder metallurgy foaming impact test three-point bending test|
Aluminum foam, which has peculiar properties (low specific weight, efficient capacity of energy absorption, thermal insulation, low magnetic permeability, excellent damping, etc.), is a new kind of functional material. However, the aluminum foam only is not suitable for some applications because of its brittleness and fragility. Traditionally, aluminum foam sandwiches are compositions of metal panels and aluminum foam core combined with all kinds of connection modes, and they offer exceptionally mechanical property compared with aluminum foam. However, these kinds of sandwiches have some demerits such as low production efficiency, poor high temperature resistance and low strength combination between panels and core, Aluminum foam sandwich is prepared by mixing elemental powders rolling, the binding between panels and core of aluminum foam sandwich is firm because it is metallurgical binding. And the mechanical properties of aluminum foam material can be improved. Aluminum foam sandwich offers low specific weight, high specific stiffness and specific strength, substantial shielding, etc. Due to their excellent performance, aluminum foam sandwiches have broad prospects of application and development in the industrial fields, such as automobile, aviation and aerospace. Aluminum foam sandwich possesses excellent comprehensive properties, and thus it is a kind of significant functional material for the development of national economics.In this work, the technical process and the basic theoretical research of preparing high-performance aluminum foam sandwich by mixing elemental powders rolling were studied. There are two distinct advantages for this technique. One is a direct recombination between the foam core and the panels can be obtained from this technique. The technique, which is a combination of rolling and powder metallurgy, can replace the conventional gluey technique. Another advantage of taking this fabrication route is that it gives an additional flexibility to incorporate elemental powders into the matrix to form the desired alloys. After uniform mixing the powders and foaming at a high temperature, near-net-shape foaming productions are easily obtained. The main contents and conclusions of this paper are as follows.The technique on preparation of aluminum foam sandwich by mixing elemental powders rolling was studied. Effects on the process of preparing aluminum foam sandwich were analyzed from three factors, cold rolling reduction ratio, foaming temperature and holding time. The effects of Si particle size and addition of Mg on uniformity and stability of the pore structure in the aluminum foam sandwich core were discussed. The heat treatment of TiH2 on the effect of aluminum foam sandwich was investigated. The combination between core and panels was analyzed. The results show that, aluminum foam sandwich with excellent pore structure can be obtained when Al and Si powders were applied as raw materials and TiH2 as foaming agent, together with the cold rolling reduction ratio kept in the range of (65-70%) and foaming temperatures and foaming times at 630-640℃,7-9 min, respectively. And heat treatment of TiH2 powders at 450℃for an hour can delay foaming and improve the pore structure. The pore structure could be improved by decreasing the particle size of Si and adding 1wt.%Mg.In order to examine the mechanical properties of aluminum foam sandwiches, the impact and three-point bending test were carried out. The interface combination between the core and the panels was explored, and the failure behaviors and the deformation characteristics of aluminum foam sandwiches were investigated. The results show that, combination between the core and the panels is excellent after impacting, and the failure behaviors of the aluminum foam sandwiches are different due to their different densities. The three-point bending test demonstrates that the pores in the aluminum foam sandwich core are destroyed gradually along the direction of stress from the upper to the lower, which means the aluminum foam sandwich possess efficient capacity of energy absorption.