新型泡沫铝的制备及其孔结构的控制

发展了一种高压渗流铸造法制备孔结构可控的新型泡沫铝，推导出孔结构参数计算公式，并据此提出孔结构参数控制和测量方法。制得的泡沫铝具有较理想的孔结构。     

Cellular Metals Manufacturing

Open cell, stochastic nickel foams are widely used for the electrodes and current collectors of metal – metal hydride batteries. Closed cell, periodic aluminum honeycomb is extensively used for the cores of light, stiff sandwich panel structures. Interest is now growing in other cell topologies and potential applications are expanding. For example cellular metals are being evaluated for impact energy absorption, for noise and vibration damping and for novel approaches to thermal management. Numerous methods for manufacturing cellular metals are being developed. As a basic understanding of the relationships between cell topology and the performance of cellular metals in each application area begins to emerge, interest is growing in processes that enable an optimized topology to be reproducibly created. For some applications, such as acoustic attenuation, stochastic metal foams are likely to be preferred over their periodically structured counterparts. Nonetheless, the average cell s ize, the cell size standard deviation, the relative density and the microstructure of the ligaments are all important to control. The invention of more stable processes and improved methods for on‐line control of the cellular structure via in‐situ sensing and more sophisticated control algorithms are likely to lead to significant improvements in foam topology. For load supporting applications, sandwich panels containing honeycomb cores are much superior to those utilizing stochastic foams, but they are more costly than stochastic foam core materials. Recently, processes have begun to emerge for making open cell periodic cell materials with triangular or pyramidal truss topologies. These have been shown to match the stiffness and strength of honeycomb in sandwich panels. New cellular metals manufacturing processes that use metal textiles and deformed sheet metal are being explored as potentially low cost manufacturing processes for these applications. These topologically optimized systems are opening up new multifunctional applications for cellular metals.     

Tensile Behaviour of Replicated Aluminium Foams

The replication process is used to produce open‐cell 99.99 % pure aluminium foams of controlled pore diameter and solid volume fraction; each parameter is varied respectively from 40 to 400 μm and 10 to 30 vol. pct. The foam tensile behaviour is consistent with the small‐strain compressive behaviour and shows a significant dependence on pore size.     

Aluminium Foam Sandwich (AFS) Ready for Market Introduction

A novel production process for aluminium foam sandwich panels (AFS) is described. As an example for a serial application of AFS a support for a mobile telescope arm on a small lorry is presented and discussed.     

Effect of composition and processing parameters on the characteristics of tannin-based rigid foams. Part I: Cell structure

Tannin-based rigid foams and derived glasslike carbon foams are new, lightweight, cellular materials, prepared from 95% natural precursors. They are mainly based on bark extracts that are cross-linked with a little of formaldehyde, in the presence of furfuryl alcohol, blowing agent and acid catalyst. Their carbonaceous counterparts are obtained by pyrolysis in inert atmosphere. Various processing and composition parameters were varied, in order to observe the resultant effects on the pore structure, i.e., cell morphology, apparent density, homogeneity, and surface area. Especially, the amounts of foaming agent, strengthener and additives (nanoclay filler) were changed, and the influences of mould diameter and compression stress during foaming were investigated as well. The foams are found to be slightly orthotropic materials whose pore structure is mainly controlled by the amount of blowing agent, leading to an easily tuneable linear cell density that typically ranges from 50 to 250 pores per inch. All the other parameters have much lower influence.     

CVD Technique for Inco Nickel Foam Production

In this paper, the capability of the CVD technique to produce uniform foams of different properties, with cell size ranging from ～ 450 to ～ 3200 μm, porosity from ～ 70 to ～ 98 %, and nominal thickness up to 3 mm is presented. In addition to the established application as a battery electrode material, some other potential capabilities and applications are explored.     

The Role of Oxidation in Blowing Particle‐Stabilised Aluminium Foams

Metal foams were produced by blowing gas into aluminium alloy melts. The effect of oxygen content of the blowing gas on composition and structure of the inner surface of the foam cells is studied by varying gas composition from argon, nitrogen and air to pure oxygen. Scanning Electron Microscopy, Auger Electron Spectroscopy and Transmission Electron Microscopy are used to analyse the surfaces. Initially particle‐free melts are pre‐treated by bubbling air through them after which a certain degree of foam stability is achieved. The oxidation products are characterised by microscopy on such foams.     

Surface Refinement of Metal Foams

Aluminium foams produced via the PM‐process are characterized by a moderate specific strength, a high surface roughness, and a poor wear behavior; to increase their mechanical properties and to improve the surface finish, wear and corrosion resistance; thermally sprayed coatings can be applied. The quality of the coating depends on the coating material, the chosen process, the preparation of the surface and spraying parameters. Aluminium alloys and iron based alloys for abrasive applications were deposited via electric arc spraying, ceramic coatings against wear were deposited by means of plasma spraying. Hard metallic coatings for severe abrasive applications were applied by high‐velocity‐oxyfuel spraying (HVOF). The results proved the suitability of this technique to significantly enhance the mechanical properties and the surface finish of metal foams. The specific strength and stiffness of the new composite materials outperform pure metal foams. The corrosion behavior was tested performing a salt spray test.     

泡沫金属的制备工艺及应用

根据泡沫金属制备过程中金属的状态,将泡沫金属的制备方法归类为:熔体凝固法、固态烧结法、金属沉积法,并按此分类对泡沫金属常用制备工艺进行了介绍.泡沫金属具有轻质、高孔隙率、电磁屏蔽等性能,按照功能用途和结构用途2方面对其应用领域进行了介绍.     

Processing of Titanium Foams

Because of their excellent mechanical properties, low density and biocompatibility, titanium foams are attractive for structural and biomedical applications. This paper reviews current techniques for titanium foam processing, which are all based on powder‐metallurgy because of the extreme reactivity of liquid titanium. A first group of processes is based on powder sintering with or without place‐holder or scaffolds. A second group relies on expansion of pressurized pores created during prior powder densification.     

Creep Response of Sandwich Beams with a Metallic Foam Core

The creep response of metallic foam sandwich beams in 3‐point bend is investigated numerically for the case of a metallic foam core and two steel faces. The face sheets are treated as elastic, while the foam core is modeled by a viscoplastic extension of the Deshpande‐Fleck yield surface. This power‐law creeping constitutive law has been implemented within the commercial finite element code ABAQUS. It is found that the beams creep by a variety of competing mechanisms, depending upon the choice of material properties and the geometric parameters. A failure map is constructed and effect of rate dependence on the load‐deflection curves is quantified, and compared against the available experimental data.