Potential New Matrix Alloys for production of PM Aluminium Foams

The powder compact melting technique for aluminium foam production as practised today accepts a certain mismatch between foaming agent decomposition and matrix alloy melting temperatures. This mismatch is believed to influence the pore structure in an unfavourable way. Adjustment of TiH₂ decomposition as well as liquidus and solidus temperatures of matrix alloys can be used to counteract it. Effects of TiH₂ thermal treatments are investigated using thermal analysis. TiH₂ variants gained via annealing treatments were used to produce aluminium foam precursor materials. As matrix for these specimens, aluminium based alloys with low liquidus and solidus temperatures were selected. Alloy systems considered include established combinations of aluminium with Cu, Mg, Si and Zn as well as special quaternary mixtures of these elements. First examinations presented include thermal analysis of alloys as well as studies on expansion vs. time and temperature relationships of precursor material based on new alloys and foaming agent variants.     

Aluminium foaming using a CO2 laser

Abstract

This paper explores the possibility of laser assisted aluminium foaming from a foamable precursor material. A preliminary study of the experimental results shows a unidirectional and localised expansion of the foam. A pore size gradient and a density gradient exist in the structure as the processing conditions change. The foam has large pores and lower density for slow processing speeds, in contrast to the case of fast processing speed where there is a small pore size but higher density. On the top surface as the melt collapses, there is a closure of pores.     

Design and manufacturing of anti-intrusion bars made of aluminium foam filled tubes

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH₂ blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed.     

The FOAMCARP process: foaming of aluminium MMCs by the chalk-aluminium reaction in precursors

A brief outline is presented of the factors involved in the search for gas-generating agents offering superior performance for foaming of liquid aluminium alloys. These include kinetic and thermodynamic characteristics of decomposition reactions, the ease of dispersion of the powdered foaming agent in the melt, the nature and likely effect of decomposition products on melt flow, potential reactions between the foaming gas and the melt and the availability, cost and ease of handling of the powder concerned. There is one very promising candidate material, calcium carbonate, which offers advantages compared to currently-employed hydride powders in virtually all aspects of their performance. It is shown that foams can be produced having appreciably finer cells (<1 mm diameter) and more uniform cell structures than currently-available melt route foams, a potentially lower ceramic content in the cell walls and dramatically reduced raw material costs. The presence of an oxidising foaming gas in the cells leads to reaction with the liquid cell surface, forming a continuous oxide film. The presence of this film has a significant effect on foam stabilisation, slowing down cell coalescence and melt drainage.     

Density and strength characteristics of foamed gypsum

This paper deals with the effect of substances producing and assisting gas and foam formation on the properties of gypsum density and strength. The gas-based foaming method utilises aluminium sulphate, potassium alum or ammonium bicarbonate for the chemical production of gas bubbles in gypsum paste. The second method obtains foamed gypsum by means of air entrainment in wet gypsum paste. The foaming agents chosen were sodium lauryl sulphate and nonyl phenol ethoxylate that are widely employed in detergent production. Five different foaming techniques are obtained with these additives required for gas and foam production. Citric acid, as retarder, and carboxyl methyl cellulose (CMC), as viscosity increasing agent, were used for promoting foam and gas formation during the foaming experiments. Aluminium sulphate was discovered to be the one that achieves the most foaming in gypsum. The techniques utilising potassium alum, sodium lauryl sulphate and ammonium bicarbonate reduced the density of gypsum products by values varying between 30% and 35%. Foaming with nonyl phenol ethoxylate had an insignificant effect on density. The addition of citric acid and carboxyl methyl cellulose assisted with density reduction. Besides regulating the hardening time, citric acid supported density reduction by releasing gas through a reaction with marble powder. However, an addition of CMC above 0.1% or 0.2% causes a density increase by preventing bubbles to expand and merge with each other. The compressive strength of low-density gypsum products falls well below 10 Mpa, stipulated by TS 370 for building gypsum.     

热塑性淀粉/高密度聚乙烯复合材料的制备及性能研究

目的 总结近年来有关植物纤维增强聚乳酸发泡材料研究的相关文献,为聚乳酸发泡材料的制备及性能研究提供参考。方法 按照发泡方法进行分类,介绍采用不同发泡方法制备植物纤维/聚乳酸复合发泡材料的性能,重点综述采用超临界CO2发泡法时,添加植物纤维对发泡材料性能的影响。 结果 植物纤维增强聚乳酸发泡材料的研究处于实验室研究阶段;添加植物纤维的聚乳酸发泡材料的泡孔尺寸更均匀、更小,泡孔密度增大,力学性能也有所提高。结论 添加植物纤维可以增强聚乳酸发泡材料的力学等性能;植物纤维和聚乳酸复合发泡材料的相关研究对聚乳酸发泡材料的大规模生产具有重要指导意义。     

植物纤维增强聚乳酸发泡材料的研究进展

目的 建立基于电感耦合等离子质谱(ICP-MS)技术的总有机锡迁移量分析方法,用于食品接触材料中总有机锡的快速筛查。方法 使用四氢呋喃溶解法筛选出添加有机锡类热稳定剂的试样,采用水和体积分数为4%的乙酸模拟物进行迁移试验,迁移温度为20 ℃和40 ℃,迁移时间为10 d,同时比较常规浸泡迁移和超声加速迁移的结果,对检测方法的精密度、准确度进行了确认。结果 总有机锡迁移测定方法在质量浓度为0.13~13 μg/L时呈良好的线性关系,采用体积分数为4%的乙酸模拟物迁移的检出限为0.011 μg/L,定量限为0.033 μg/L;水模拟物迁移的检出限为0.0097 μg/L,定量限为0.029 μg/L。总有机锡加标回收率范围为98.1%~109.9%,相对标准偏差(RSD)<4.5%。结论 此方法具有灵敏度高、选择性好和准确性高等特点,适用于PVC包装材料中总有机锡迁移量快速分析。     

A classification of studies on properties of foam concrete

Though foam concrete was initially envisaged as a void filling and insulation material, there have been renewed interest in its structural characteristics in view of its lighter weight, savings in material and potential for large scale utilization of wastes like fly ash. The focus of this paper is to classify literature on foam concrete in terms of constituent materials (foaming agent, cement and other fillers used), mix proportioning, production methods, fresh and hardened properties of foam concrete. Based on the review, the following research needs have been identified: (i) developing affordable foaming agent and foam generator, (ii) investigation on compatibility between foaming agent and chemical admixtures, use of lightweight coarse aggregate and reinforcement including fibers, (iii) durability studies, and (iv) factors influencing foam concrete production viz., mixing, transporting and pumping.     

Laser additive manufacturing foam aluminium-12 wt-% silicon with different addition TiH2 foaming agent

The aim of this work is to study the effects of laser additive manufacturing on microstructure and mechanical properties of foam Al–12?wt-%Si aluminium alloy with/without TiH₂ foaming agent. The results showed that low porosity closed foam Al–12Si was successfully obtained. The effect of processing parameters on the porosity is discussed. The porosity was changed from initial 20.9% without foaming agent to 32.3 and 45.9% with 5 and 10% addition of foaming agent, respectively. Average micro-hardness values of the obtain foam Al–Si alloy is varied from 100 to 130?HV and the shape of compressive stress–strain curve is as the same as foam aluminium made by powder metallurgy and casting methods.     

Microstructure of high-strength foam concrete

Foam concretes are divided into two groups: on the one hand the physically foamed concrete is mixed in fast rotating pug mill mixers by using foaming agents. This concrete cures under atmospheric conditions. On the other hand the autoclaved aerated concrete is chemically foamed by adding aluminium powder. Afterwards it is cured in a saturated steam atmosphere.New alternatives for the application of foam concretes arise from the combination of chemical foaming and air curing in manufacturing processes. These foam concretes are new and innovative building materials with interesting properties: low mass density and high strength. Responsible for these properties are the macro-, meso- and microporosity. Macropores are created by adding aluminium powder in different volumes and with different particle size distributions. However, the microstructure of the cement matrix is affected by meso- and micropores. In addition, the matrix of the hardened cement paste can be optimized by the specific use of chemical additives for concrete.The influence of aluminium powder and chemical additives on the properties of the microstructure of the hardened cement matrices were investigated by using petrographic microscopy as well as scanning electron microscopy.     

泡沫镁制备技术研究现状及其在航空航天领域的应用前景

泡沫镁作为一种新型功能材料,近年来逐渐受到了国内外的广泛关注,但由于镁过于活泼,易引起爆炸,难以在生产中被大量使用,故关于泡沫镁的研究较少。主要综述了泡沫镁阻尼性能、吸声性能、吸能性能、散热性能、生物医学性能和电磁屏蔽性能等几种主要的性能特点,进而综述了粉末冶金法、熔体发泡法、渗流铸造法等几种常见的泡沫镁材料制备工艺的研究进展,并结合笔者的研究理解对几种制备工艺进行了对比,分析了各种制备方法的优缺点。在此基础上对泡沫镁材料在航空航天领域上的应用进行了分析,表明了其在航空航天领域有着广阔的应用前景。     

高效复合类发泡剂的制备及其性能研究

泡沫混凝土具有容重轻、自立性强及防渗性好等特点,是一种新型港口码头挡土墙回填材料,其中发泡剂的研制对泡沫混凝土的性能起着至关重要的作用。本文制备的发泡剂是以浓度为0.8%的α-烯基磺酸钠溶液为发泡剂母液,选取稳泡物质A、B、C和D对母液进行稳泡改性,并对泡沫性能进行分析研究。该发泡剂制备的泡沫表面光泽细腻,稳定性较好,其中发泡倍数为46.7倍,1 h沉降距为1.2 mm,1 h泌水量为15.7ml,将该发泡剂应用于挡土墙回填用泡沫混凝土,产品表现出了较好的力学性能和抗渗性能。     

Viewing the Early Stage of Metal Foam Formation by Computed Tomography using Synchrotron Radiation

Foamed aluminium alloy containing 7 wt.‐% of Si is investigated by μm‐resolved X‐ray computed tomography (CT) using synchrotron radiation. The foam is fabricated employing a powder metallurgical route. The evolution of foam microstructure is characterized by studying a series of samples representing different stages of foam expansion obtained by interrupting the foaming process for each sample at different foaming times. The computer tomographic reconstruction provides a 3D image of the pore structure as well as the spatial distribution of blowing agent particles. A statistical evaluation allows to determine the size distribution of the blowing agent and of the pores at different foaming stages.     

Effects of aluminium powder content and cold rolling on foaming behaviour of xAlp/Al5Si4Cu4Mg/0.8TiH2 composites

Abstract

Aluminium foams were produced by applying powder metallurgy technology. The process began by making aluminium powder and mixing it with alloy powder (Al5Si4Cu4Mg) and foaming agent (TiH₂). The mix was compacted to the form of a billet by cold pressing and then it was hot extruded to a dense foamable strip, which was cold rolled to give 40% thickness reduction. The resulting precursor composites of both the extruded strip and the extruded plus rolled strip were then freely foamed without a mould at a constant temperature of 700°C for different foaming times. The effects of aluminium powder content and cold rolling on the foaming characteristics of the foamable composite strip were studied. It is noted that aluminium powder fibre in the extruded composite strip acts as a barrier to pore initiation and evolution due to the higher melting point of pure aluminium fibre than that of the alloy matrix. Cold rolling promotes foaming of the composite strip due to the TiH₂ cracking and debonding between TiH₂ particles and metal matrix. The morphological and microstructural evolution of composite foams was also investigated. The foaming mechanism can be described by the following sequence: cracklike pore nucleation between elongated powder fibres; ellipsoidal, spherical, and polygonal pore growth; and the collapse of pores as a result of coalescence.     

Editorial

In this study the Taguchi method is used to find the optimal process parameters for aluminium foam manufacturing. Porous metals are the unique materials used for light weight structural components, for filters and electrodes and for shock or sound absorbing products. Recently, interesting foaming technology developments have proposed metallic foams as a valid commercial chance. Metallic foam manufacturing techniques include solid state powder methods, gas blowing processes, metal deposition onto a polymer precursor and liquid state processing. The aluminium foams presented in this study are produced by the powder metallurgy route starting from aluminium powders with titanium hydride as the foaming agent. During the experimental work, many samples are made by utilizing the combination of process parameters based on Taguchi orthogonal design. Three manufacturing parameters are studied: the silicon carbide content in powder mixture, the compaction pressure and the foaming temperature. The Taguchi method is applied to design an orthogonal experimental array and a multi-objective optimization approach is then proposed by simultaneously minimizing the relative density and maximizing the absorbed energy. Verification test is also performed to prove the effectiveness of the presented technique.     

Verbundwerkstoffe mit Aluminiumschaum – Anwendungen im Schienenfahrzeugbau

Aluminium foam composites – applications in railroad manufacturing After their rediscovery in the beginning of the 90ies foamed metals are now being produced on an industrial scale. In most applications the aluminium foam is used as composite material, i.e. in combination with other materials. The composites can be distinguished into flat or complex shaped sandwich structures on the one hand, and 3‐dimensional shaped foam parts on the other hand. The processes and feasible geometries are described. The material properties and the industrial applications are illustrated. Within a publicly funded project the utilisation of sandwich composites with an aluminium foam core layer was evaluated regarding applications for railroad vehicles. The central aim of the investigation was the production of a large segment of the vehicle’s front module. Results of this project are presented.     

Aluminium foam–polymer composites: processing and characteristics

Dissemination of closed cell metal foam unique properties (low density, efficient energy absorption, high vibration/sound attenuation) in real life products has often been difficult to realise. With advanced pore morphology (APM) aluminium foam–polymer hybrids a new and simplified process route targeted at application in foam-filled structures (e.g. automotive A-pillar) has been introduced. APM foams are made from spherical, small volume foam elements joined to each other in a separate process step. Joining the aluminium foam elements by adhesive bonding delivers composite foam with approximately 80–95 wt.% aluminium foam and 5–20 wt.% adhesive (polymer). Setting up cellular structures from spherical foam elements allows for automatic part production, good pore morphology control and cost effective aluminium foam application. An automated production line is displayed and discussed. Mechanical properties of APM aluminium foam–polymer hybrids are similar to other closed cell aluminium foams. Integration of APM foams in profiles resulted in significantly improved properties as observed for conventional closed cell aluminium foam fillings. The unique properties of APM composite foams make them an attractive alternative as a cost effective and easily applicable material of construction with targeted uses such as energy absorbing reinforcement of composite structures.     

泡沫金属的制造方法

概要叙述了泡沫金属的特性，制造方法及用途，并以泡沫铝为例，着重介绍了发泡法的原理及过程，指出了泡沫金属制造技术上应该解决的问题。     

Deformation characteristics of metal foams

The deformation behaviour of a series of aluminium and zinc foams was investigated by uniaxial testing. Because the deformation behaviour of metal foams is expected to be anisotropic owing to the existence of a closed outer skin and with respect to the foaming direction, a series of measurements was carried out where the orientation of the outer skin and the foaming direction were varied. Stress–strain diagrams and corresponding compression strengths were determined for aluminium- and zinc-based foams. The influence of an age-hardening heat treatment was investigated. Finally, the axial deformation behaviour of aluminium tubes filled with aluminium foam was tested under uniaxial loading conditions. The results of the measurements are discussed in the context of possible applications of metal foams as energy absorbers. © 1998 Chapman & Hall     

Effect of the interface bonding on the mechanical response of aluminium foam reinforced steel tubes

Aluminium foams have been recently proposed as filling reinforcements to improve impact behavior of hollow components used as protection systems in vehicles. In this study, aluminium foam filled stainless steel tubes have been prepared by directly foaming metal powder compacts inside the tubes. Attention was concentrated on the interface phenomena that characterize the core–shell interaction and the process parameters determining the metallurgical reactions between the two alloys. The formation of binary and ternary intermetallic compounds was observed at the aluminium/steel interface whenever the growth of the oxide layer on the foam surface in foaming was constrained. Compression tests of the reinforced tubes confirmed a maximized energy absorption in coincidence with the formation of the interface bonding. In those cases, extended foam intrusions into compressed tube folds were observed. The microstructural investigation revealed that in the transition zone the intermetallic layer strength was comparable to that of the foamed matrix.