热压注成型ZrSiO4—MgO—Al2O3三元复合直孔陶瓷过滤器的研究

介绍了热压注法成型ＺｒＳｉＯ４－ＭｇＯ－Ａｌ２Ｏ３三元复合材料直孔陶瓷过滤器的工艺，采用优化设计方法研究了ＺｒＳｉＯ４－ＭｇＯ－Ａｌ２Ｏ３三元复合陶瓷过滤器材料的配比，进行了过滤钢水的试验。结果表明，该种过滤器具有良好的性能与应用效果。适合于工业化大批量生产。     

直接发泡法制备泡沫陶瓷过滤器

介绍了一种新型泡沫陶瓷过滤器的制备方法并对其性能进行了测试研究。首先制备凝胶注模成型所需氧化铝陶瓷浆料，再添加吐温（Tween）和曲通（Triton）系列表面活性剂，通过机械搅拌使其直接发泡，再通过有机单体丙烯酰胺聚合，固化泡沫浆料，成型得到坯体，经干燥、烧结之后，制备成氧化铝泡沫陶瓷。研究了该工艺所成型泡沫陶瓷气孔率和通孔率（开孔气孔率）的关系，结果表明，直接发泡法可以制备高通孔率的泡沫陶瓷，能够满足过滤器使用时高开孔率和高强度的要求。     

热压铸成型ZrO2—Al2O3—MgO三元复合直孔陶瓷过滤器的研究

采用混料最优设计的方法研究了ＺｒＯ２－Ａｌ２Ｏ３－ＭｇＯ三元复合材料的配比，及其成型工艺。进行了直孔过滤器过滤钢水效果试验。结果表明，在研究的范围内直孔过滤器的最适宜配比为：ＺｒＯ２：Ａｌ２Ｏ３：ＭｇＯ＝９２．５：２．８８：４．６２；通过过滤净化后４５＾＃钢的强度提高了１５％，冲击韧性提高了３４％。     

用陶瓷过滤器去除钢液中的Al_2O_3夹杂物的实验研究

用陶瓷泡沫过滤器、多孔过滤器和环形过滤器对用真空感应法生产的，且用AI脱氧的50kg铁水进行Al2O3夹杂物过滤的试验。根据化学分析得出的总氧含量计算过滤效果．结果表明：用泡沫过滤器过滤纯铁水最好效果达90％，最低氧含量MO～30μg／g，且与铁水中原始氧含量无关。用多孔过滤器对铁水进行过滤的过滤率达80％，直径大于20μm的夹杂物全部去除。用不同直径纤维的环形过滤器对铁水进行试验，Al2O3夹杂去除率在72％～84％之间。实践证明：以上3种陶瓷过滤器对去除钢液中的Allo．夹杂物均为有效，夹杂物的分离率都很高，但是，当钢水量较…     

铸钢用泡沫陶瓷过滤器的研制及应用

论述了在１５００－１６００℃温度下，烧结制备铸钢用增韧泡沫陶瓷过滤器的工。屏在正交设计的基础上取样进行了Ｘ射线衍射分析，扫描电镜形貌观察及性能测试，从而获得了烧结制备铸钢用泡沫陶瓷过滤器的最佳配方。采用所制备的泡沫陶瓷过滤器对ＺＧ４５进行了过滤试验，结果表明，所制备的增韧泡沫陶瓷过滤器能够过滤净化钢液，过滤净化后的ＺＧ４５力学性能有显著改善。     

过滤器过滤性能优劣的判定方法

介绍了过滤器的主要过滤性能指标,根据这些指标在过滤与净化中的作用对其进行了权重分级,给出了过滤器过滤性能优劣判定的定量表述方法。     

液压系统污染控制动平衡研究

分析了液压系统的污染来源，通过实验检测了实际液压系统过滤器的过滤比远低于理论过滤比，并提出影响过滤性能的过滤器吸附率的概念，据此推导了液压系统简化的污染控制动平衡方程，并给出了近似条件下的解。本文的实验和理论研究对液压污染控制系统的设计具有指导意义。     

过滤工艺对铝电阻率的影响

主要研究了过滤器孔径、工作压头及温度等因素对铝电阻率的影响，研究结果表明合理的过滤工艺可以有效地降低铝的电阻率。工业纯铝和含硼铝经细孔过滤器过滤，可以降低电阻率0．32％和1．34％，为高电导率铝合金的开发应用提供必要的参考数据。     

大尺寸轻型碳化硅质反射镜素坯的凝胶注模成型

利用凝胶注模成型工艺制各了大尺寸轻型碳化硅(SiC)质反射镜素坯.讨论了SiC的颗粒级配、固相含量对浆料性能的影响以及催化剂、引发剂、浆料温度对凝胶时间的影响.结果表明:最佳分散条件下固相含量为65%的SiC水基浆料具备良好的流动性,适于进行凝胶注模成型;引发剂加入量为20 mmol/L浆料,与催化剂的摩尔比为5:1,浆料温度降到15℃时,凝胶时间能够满足注模及成型所需.最终测试了反应烧结后SiC陶瓷的性能.     

熔模铸造的过滤技术研究

研究了在熔模铸造中净化碳钢钢水的过滤技术。对不同过滤器在模组中的安放位置作了研究;比较了过滤和未过滤试样的力学性能、金相组织和断口形貌;研制了适用于熔模铸件的过滤器,并在生产中进行了应用试验。研究结果表明,试验所用的过滤方法,能改善合金性能、有效地去除钢中非金属夹杂物,所研制的熔模铸造过滤器对提高铸件质量有实用意义。     

Joining stainless steel metal foams

Abstract

Metallic foams produced from stainless steel are one of the most recently developed ultralightweight materials. These foams have very low densities and high energy absorption capacities and are therefore expected to have widespread applications in the manufacture of ultralightweight structural components. The fabrication of load bearing structural components such as implants, and high temperature air or fluid filters, are potential application areas depending on the form of the cell structure of the foam. Closed cell metal foams are typically suitable for structural uses whereas open cell foams tend to be preferred for functional applications. Development of adequate joining technologies for these materials is an essential step for their widespread industrial utilisation. The present paper describes a brazing method that is capable of providing excellent joints between 316 stainless steel foams and a conventional 316 stainless steel bulk alloy. Having optimised the bonding conditions and using a Cu–Ti alloy as the filler metal, bonds between a foam and a bulk alloy were produced. No apparent plastic deformation of the metal foam occurred in the course of the 10 min length brazing process, and the resulting bonds had tensile strengths higher than that of the stainless steel foam.     

Compressive properties of open-cell ceramic foams

The compressive experiments of two kinds of ceramic foams were completed. The results show that the behavior of ceramic foams made by organic filling method is anisotropic. The stress-strain responses of ceramic foams made by sponge-replication show isotropy and strain rate dependence. The struts brittle breaking of net structure of this ceramic foam arises at the weakest defects of framework or at the part of framework, which causes the initiation and expanding of cracks. The compressive strength of ceramic foam is dependent on the strut size and relative density of foams.     

Foam topology: bending versus stretching dominated architectures

Cellular solids can deform by either the bending or stretching of the cell walls. While most cellular solids are bending-dominated, those that are stretching-dominated are much more weight-efficient for structural applications. In this study we have investigated the topological criteria that dictate the deformation mechanism of a cellular solid by analysing the rigidity (or otherwise) of pin-jointed frameworks comprising inextensional struts. We show that the minimum node connectivity for a special class of lattice structured materials to be stretching-dominated is 6 for 2D foams and 12 for 3D foams. Similarly, sandwich plates comprising of truss cores faced with planar trusses require a minimum node connectivity of 9 to undergo stretching-dominated deformation for all loading states.     

Deformation stabilization of lattice structures via foam addition

Stochastic foams are soft but absorb energy efficiently under compressive loading; in contrast, periodic lattice structures are strong but generally exhibit poor energy-absorbing characteristics. Here we present and assess a hierarchical composite concept that aims to combine the desirable attributes of stochastic foams and lattice structures. The composite comprises a low-density polymer lattice structure with centimeter-scale voids and stochastic foam with pores in the sub-millimeter scale in the spaces between the lattice struts. The assessment is made on the basis of compressive response. We show that the post-yielding strength of the lattice can be doubled with the addition of even a weak (low-density) foam: the strength exceeds the combined contributions from the lattice structure and the foam alone. Addition of slightly denser foams can lead to an even larger strength increase. Using X-ray computed tomography, we show that the strength elevation is attributable to the stabilization of the strut members against buckling when surrounded by foam. Finite-element calculations of lattice structures alone and lattice/foam composites show similar characteristics. This composite concept may allow attainment of combinations of strength and energy absorption capacity that cannot be accessed by either foams or lattice structures alone.     

Manufacturing routes for metallic foams

The study of metallic foams has become attractive to researchers interested in both scientific and industrial applications. In this paper, various methods for making such foams are presented and discussed. Some techniques start from specially prepared molten metals with adjusted viscosities. Such melts can be foamed by injecting gases or by adding gas-releasing blowing agents which cause the formation of bubbles during their in-situ decomposition. Another method is to prepare supersaturated metal-gas systems under high pressure and initiate bubble formation by pressure and temperature control. Finally, metallic foams can be made by mixing metal powders with a blowing agent, compacting the mix, and then foaming the compact by melting. The various foaming processes, the foam-stabilizing mechanisms, and some known problems with the various methods are addressed in this article. In addition, some possible applications for metallic foams are presented. Editor’s Note: A hypertext-enhanced version of this article can be found at www.tms.org/pubs/journals/JOM/0012/Banhart-0012.html For more information, contact John Banhart, Fraunhofer-Institute for Manufacturing and Advanced Materials, Wiener Str. 12, 28359 Bremen, Germany; e-mail banhart@telda.net.     

石膏型渗流法制备的开孔泡沫铝的压缩行为研究

本文采用可溶石膏型预制块,通过加压渗流的方法制备了泡沫纯铝、泡沫ZL101合金和泡沫ZL102合金,并通过准静态压缩实验研究了3种不同基体材料的泡沫铝的压缩行为及吸能性能.结果表明:通过石膏型渗流法制备的开孔泡沫铝合金的孔隙率可以达到85％～93.5％;泡沫铝基体材料的力学性能对泡沫铝压缩力学性能有重要影响;泡沫ZL1...     

Novel manufacturing process of closed-cell aluminum foam by accumulative roll-bonding

A new manufacturing process for closed-cell aluminum foams was developed using bulk aluminum sheets as a starting material. Aluminum preform containing titanium hydride powder was successfully produced through accumulative roll-bonding (ARB). Heating the preform sheets under the controlled temperature conditions, we obtained foamed aluminum plates of about 40% porosity.     

石膏型渗流制备泡沫铝填充圆管压缩行为研究

采用石膏型渗流制备开孔泡沫铝并填充到薄壁圆管,制成泡沫铝夹心管。通过准静态压缩试验研究了泡沫铝夹心管的压缩行为。结果表明：采用石膏型渗流法制备的泡沫铝孔隙率在85%左右,其压缩变形阶段可分为弹性段、塑性平台段和致密化段;空心圆管的压缩行为与其本身的结构参数有关;泡沫铝夹心管的力学性能与吸能能力比空心圆管和泡沫铝有了一定的提高,且石膏型渗流法所制泡沫铝夹心管质量较轻。     

Pyrolysis of polyurethane by microwave hybrid heating for the processing of NiCr foams

Reticulated polyurethane foams are often used as templates for the processing of metal and ceramic foams, since polyurethane foams with a high homogeneity and uniformity of pores and a wide variety of porosities and pore sizes are commercially available. Current conventional methods to pyrolyse polyurethane have brought attention to issues such as long processing time, high costs and high contents of carbon residue. Microwave hybrid heating, as a new pyrolysis method, has been investigated in this research to overcome these issues. Two microwave hybrid and one conventional heating process as comparison were performed to pyrolyse binder and polyurethane for the processing of NiCr8020 foams, which were fabricated by dip-coating method in a powder metallurgical route. Compared to the conventional process, the processing time and residual carbon content of the pyrolysed and pre-sintered foams can be reduced significantly by utilizing microwave hybrid heating techniques, whereas the stability of microwave hybrid heating must be improved and a compromise must be made between the heating rate and the residual carbon content due to the formation of burst holes during the rapid decomposition of polyurethane.