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By Lucas L. Costa, Luiz F. Lopes, Ludy C. Motta, Felipe P. D. Lopes, Sergio N. Monteiro, Lara S. Vasconcellos

"Environmentally correct materials like the lignocellulosic natural fibers, which are renewable and biodegradable, are being extensively investigated as possible substitutes for synthetic fiber in polymeric composites. Several natural fibers have never been thoroughly investigated as possible composite reinforcement. The fiber obtained from the leaves of the buriti (Mauritia flexuosa) palm tree is one example. Therefore, the objective of this work was to study the properties of buriti waste fibers, in amounts of up to 30%, reinforcing polyester composites.IntroductionIn the past century, the technological development gave priority to new synthetic materials with energy intensive methods of production. Today, there is a concern that conventional energy source such as petroleum, natural gas and coal are the main responsible for global warming. Therefore, the use of natural materials is gaining attention not only for the saving in process energy but also the renewable and biodegradable characteristics that make them environmentally correct. The lignocellulosic natural fibers extracted from cultivated vegetables like jute, sisal, hemp, coconut, flax, ramie and many others are typical examples. This type of fiber is being extensively investigated as a possible substitute for synthetic ones, especially the glass fiber, as composite reinforcement [1].A relevant example of lignocellulosic fiber substitution is nowadays occurring in vehicles. The automobile industry is applying composites reinforced with natural fibers to replace parts such as panels and seat cushions made of fiberglass or polymeric foams [4], as illustrated in Fig. 1. The practical reasons for this preference are that natural fiber composites present less damage to tools and molding equipments as well as relatively better finishing and less abrasive surface than corresponding parts made, for instance, of glass fibers. On top of these advantages, low cost is probably the main motivation for the industrial interest for natural fiber composites, especially in the case of residual fibers [5] or post-used fabrics such as jute sackcloth [6]. Natural fibers, however, are hydrophilic and will not form strong bonding with a hydrophobic polymer, normally used as composite matrix [1-3]. Another disadvantage is the heterogeneous characteristics of a natural fiber, which is typical of biomaterials. This results in a relatively great dispersion of dimensions and properties values such as the mechanical strength [1-3]."

Jan 1, 2008

By Yong Hack Lee

Nonferrous smelting processes have been through a rapid transformation since the beginning of 1980. The copper smelting technology has changed from the conventional Blast Furnace process to the Flash Smelting and MIB process. In the field of lead smelting, the technology has changed from the Blast Furnace Smelting to the Direct Smelting such as QSL and KIVCET. In 1992, Onsan Refinery successfully commissioned Direct Smelting QSL technology for lead. The QSL could produce more than 160,000 ton per year of lead bullion from lead concentrate and various residues. Moreover, since the year 2000, the TSL (Top Submerged Lance) Technology utilizing the same Direct Smelting process has been successfully commissioned to treat lead concentrate as well as lead sulfate residue produced from a hydrometallurgical zinc plant. This paper presents and compares the energy flows of lead smelting processes such as a conventional process and the Direct Smelting Processes plotted on the Pb-O-S phase diagram. The oxygen potential diagram suggests how to control the oxygen potential in the furnace. Also, it describes the recent operational experience in the TSL plant of Onsan Refinery with necessary mass balance of key elements.

Jan 1, 2003

By Micheal McCarter, Biswadeep Saha, Meenakshisundaram Ramanathan, Chai Ren, Sivaraman Guruswamy

"Three-point bend test was used to study the effect of electrochemically charged hydrogen and magnetic field on the embrittlement behavior of AISI 4340 steel in this work. Acoustic emission signals were collected during the test and analyzed to gain an understanding of the crack growth process. Cathodic hydrogen charging in AISI 4340 steel resulted in drastic reduction of ductility and strength. Hydrogen embrittlement was characterized by a change in fracture surface from dimpled ductile surface to quasi cleavage type fracture. No significant effect was observed in the presence of magnetic field. The acoustic emission signals collected during the test provided an indication of the extent of energy released during the crack growth process.*Support of this work by NSF through the award DMR-0854166 is gratefully acknowledgedIntroductionGrowing interest in hydrogen as a clean fuel and use of steel and other iron based alloys for storage and transport of hydrogen has led to extensive study of the influence of hydrogen on the mechanical properties of these alloys. Hydrogen interaction with materials may result in degradation of mechanical properties. Embrittlement, either ductile or brittle, can be described as a condition which decreases the toughness of the material or increases the ease of crack growth. Hydrogen present even in few parts per million is sufficient to embrittle steels at room temperature [1]. In most cases, hydrogen exposure is through an electrochemical process in aqueous corroding environments. In such cases, they are prone to be exposed simultaneously to electrically induced magnetic fields, which are also believed to affect the hydrogen embrittlement susceptibility of these alloys. So it is also important to study the effect of magnetic field on the hydrogen embrittlement susceptibility. Hydrogen solubility by electrochemical process in aqueous solution is proportional to square root of current density for iron. [2,3]"

Jan 1, 2012

By David E. Hardt

"One of the critical variables to be controlled during arc welding is the size or geometry of the weld pool. The measurement of pool geometry has become an increasingly important problem with the advance of welding automation and control, and this paper addresses that problem. The basic concept of pool size estimation via measurement of pool dynamics is presented. The theory underlying this concept is discussed and is followed by a review of the current work in this area. It is concluded that pool dynamics can be characterized by natural frequencies of oscillation, for stationary welds, and that these can be measured by appropriate signal processing performed on the arc voltage. However, it appears that only full penetration welds show a strong correlation between weld size and natural frequency. Also, the extension of these results to the realistic case of moving welds has yet to be considered in detail. Nonetheless, this method of in-process measurement for real-time weld process control is still quite attractive where applicable since it can be accomplished simply by modifying the arc current schedule and by signal processing of the arc voltage.INTRODUCTUIONThe study of welding process control has been dominated by research into methods of in processing sensing of the weld pool geometry. While it has been shown feasible to measure the topside pool geometry using video methods [1,2], the penetration or backside bead width have remained elusive quantities. This is particularly true if a topside sensor location is required.The concept of using weld pool motion as a pool geometry sensing method was proposed by Hardt et al. [3] and later demonstrated by Hardt and Zacksenhouse [5] and Richardson and Renwick [6]. The concept is based on the fluid dynamics of a pool constrained by a solid container and by significant surface tension forces (i.e. a small shallow pool, not a ""pond"" or ""lake""). Such a pool, if subjected to external forces, will exhibit a surface motion is a function of that force, the properties of the fluid, the surface tension, and the shape of the container. Thus, if this motion can be excited and measured, and the relationship to the pool geometry determined, a means of sensing pool shape will exist."

Jan 1, 1986

By Toshiyuki Kozuka

CdTe metal composite semi-conducting material has high potential in good performance of energy conversion efficiency for solar cell and there is much room for improvement of the performance by developing a process of making a thin CdTe film. In this paper, the imposition of intense magnetic field on CdTe electro-depositing surface is proposed, which is one of the possibilities for improving the energy conversion efficiency. In the experiment, cryogen-free super-conducting magnet up to 5T was used and CdTe film was deposited electrically in -0.72V vs. SHE The electrolyte was Cd and Te ammonia alkali solution with controlled temperature in the acrylic cell of 70mm diameter. Electro-deposition behavior of CdTe has affected by the imposition of the intense magnetic field due to microscopic convection in the vicinity of the depositing surface. Electro-deposited surface of CdTe becomes smooth due to microscopic convection around the surface, and the crystallization behavior is also affected, where crystallization temperature and the grain size is changed by the imposition of intense magnetic field.

Jan 1, 2003

By L. Katgerman, R. Van Toi, H. E. A. Van den Akker

"Mould filling simulations are powerful tools for optimizing the characteristics of castings. The robustness of calculational methods for mould filling simulations is generally tested in simple geometries. While a vertical plate has been used often for validation studies, this paper aims at mould filling simulations of a horizontal thin wall casting. Such castings exhibit a strong interaction between heat transfer (solidification), surface tension and gravitational force.The results are presented of a study to validate numerical simulations of mould filling phenomena in a thin wall horizontal casting. Solidification during mould filling is studied computationally. Velocities are measured using Particle Image Velocimetry.INTRODUCTIONIn foundry practice Computational Fluid Dynamics (CFD) is being considered a promising tool to arrive at a better understanding of casting defects introduced during the mould filling period of a casting. The use of CFD is believed to be advantageous in predicting possible defect locations, pouring times, and the lowest possible casting temperature without the risk of cold shuts. In addition, CFD may be used to optimize pouring system geometries [1,2]. As opposed to experimental studies in, e.g., cold water models, CFD allows for the flexible modification of the casting geometry and the pouring system, and for the inclusion of physical effects such as solidification and heat transfer. Thus, a proper use of CFD may lead to a reduction of the casting rejection rate without expensive trial-and-error procedures, and to a decrease of production costs in foundries. Mould filling simulations take a special place in CFD, because a free surface tracking algorithm is required. Over the past decade methods, MAC [3] and SOLAVOF [4], have been extended to 3-D. The robustness of computational methods for mould filling simulations is generally tested in simple geometries [5,6]. While a vertical plate has been used often for validation studies, this paper concentrates at mould filling simulations of a horizontal thin wall casting. Thin wall horizontal castings exhibit a strong interaction between heat transfer (solidification), surfaces tension and gravitational force. The gravitational force in this setting is orthogonal to the plane of flow and has therefore no influence on the shape of the free surface in the plane of flow. Mould filling numerical methods and algorithms have been recently reviewed by Chen et al.[7]."

Jan 1, 1999

By A. P. Paiva

Although the advantages of Solvent Extraction for separation/purification of relatively concentrated solutions are well known in Extractive Metallurgy, its use for the recovery of elements present in low levels only recently has been discussed, with particular attention devoted to precious metals. In this work, the extraction behaviour of Cyanex 471X towards silver, from an acidic chloride medium is reported, the extraction and stripping isotherms and related kinetic features analysed. Results on the selectivity of silver extraction against high contents of iron, copper and lead are discussed. Phosphine sulphide extractants are generally associated with solvation mechanisms: analysis of the extraction pathways along with the possibility of reaching a suitable loading in the organic phase are also presented.

Jan 1, 1993

By Jilai Xue, Jun Zhu, GermainKouma Ndong, Luxing Feng

High-temperature corrosion behaviors of Fe-Ni-Cr alloy as inert anodes for aluminum electrolysis have been studied. The effect of anodic overpotential on layer growth of anodic surface is specially considered. The corrosion layers on the anodes tested were analyzed using XRD and SEM-EDS to provide a fundamental understanding of the layers growth at metallic anode surface. The dissolution of the scale layers on the metal anode occurred with low overpotential, while AlxM3-xO4 spinel phase within the scale layers was found with an increased overpotential. A mixture of multiple MyO layers existed on the anode substrate. The results may be useful for understanding and controlling the corrosion behaviors of Fe-Ni-Cr anode for potential application in aluminum electrolysis.

Jan 1, 2015

By G. R. Adams, N. Y. Tang, N. Qiang

"Aluminum is the most important alloy addition to Zn baths for controlling the reaction kinetics between the steel substrate and molten Zn in continuous galvanizing operations. Due to the complexity of the Zn-Fe-Al ternary system, the measurement and control of effective bath Al remains a challenge for modem galvanizers. The successful development of Al sensors has made the real-time measurements of bath Al contents possible. To facilitate their application, a computer interface and a palm-size data logger have been developed by Cominco. Plant applications indicated that the sensor possessed sufficient accuracy for process monitoring and control. The working mechanism of the Al sensors and Cominco's development work is described, and the results of sensor applications are presented.IntroductionControl of bath Al content is critical in modem continuous galvanizing because it has a strong influence on coating structure and properties and the overall product quality. The control of effective bath Al content (Al in liquid solution) is particularly critical for galvannealing where a high bath Al content may lead to incomplete alloying during post annealing, and a low bath Al content may result in other operation problems, such as excessive bottom dross accumulation and difficulties in coating thickness control. The desirable accuracy of the Al control is within ±50 ppm of target levels. In principle, such an accuracy is achievable for modem chemical analysis facilities, such as atomic absorption photospectrometer (AAS) and induction-coupled plasma (ICP). However, a recent study carried out by the International Lead and Zinc Research Organization (ILZRO) indicated that such an accuracy is rarely achieved in the zinc and steel industries.(1)"

Jan 1, 1997

By D. C. Azubike

Wolframite (FeWO4) usually having cassiterite (SnO2) as a major impurity is a primary source of tungsten. Its direct reduction/carburisation with carbon in the temperature range 1000-1400°C, and with hydrogen at 600-900°C followed by carburisation with CO at 900°C are described. Depending on the conditions and reactants employed, Fe, Fe2W, B-Sn,WC, W2C, Fe3W3C and Fe6W6C are the products. Tin was found to inhibit the overall reduction and carburisation reactions significantly. The potential for either efficient separation of iron and tungsten or a one-stage production of an iron-based metal carbide composite is discussed.

Jan 1, 1992

By J. K. Brimacombe, I. V. Samarasekera, B. G. Thomas

"Mathematical models have been developed for the processing of static cast steel ingots and are app1ied to investigate the mechanisms for the formation of panel cracks. Panel cracking is an intermittent but persistent defect that causes affected steel ingots to be scrapped. A two-dimensional, finite-element, heat-transfer model was formulated and employed to calculate the temperature distribution in both large and small steel ingots during the various processing stages from initial casting to the start of rolling, including solidification, cooling in the mold and in air, reheating in the soaking pit, and subsequent air cooling. The stress state in the ingot arising from the calculated temperature variations was then determined. This involved the development of a transient, elasto-visco-plastic, finite element, thermal stress model, including the effects of phase transformation volume changes and kinetics creep, and temperature-dependent, mechanical properties. The results of the mathematical model predictions of temperature and stress were then used to determine the mechanisms and to suggest solutions for two different types of panel crack formation. Mid-face panel cracks apparently form during air cooling when the mid-face surface temperature is between the Arl and 500~C. Off-corner panel cracks appear to initiate internally during the early stages of reheating but do not propagate to the surface until much later. IntroductionPanel crack formation in static-cast steel ingots is a defect that has been plaguing the steel industry for several decades. Although the problem is intermittent, it is also serious since affected ingots must be scrapped. Panel cracks are manifested as two distinct types of cracking problems. ""Mid-face"" panel cracks are found exclusively in small, 2 to 6 ton, medium carbon steel (0.3 to 0.7% C) ingots and usually exhibit a single, continuous, longitudinal crack down the center of one of the ingot faces as shown in Fig. l (l). ""Off-corner"" panel cracks often form roughly oval, discontinuous crack patterns on the wide faces of large, 20 to 30 ton ingots as seen in Fig. 2 (2). They affect only low carbon steels (0. l to 0.2% C) with high manganese content. Both defects affect only aluminum-treated steels and are caused by a combination of intermediate temperature ductility loss involving aluminum-nitride precipitation and thermal stress generation. The ductility problem has received a good deal of attention which was the subject of a recent review (3). The present study was undertaken to investigate the thermal stress aspects of the problem through the development of mathematical models of heat transfer and stress generation in static-cast steel ingots. The ultimate objective was to elucidate the mechanisms of formation for both types of panel crack and to evaluate possible solutions to the problem."

Jan 1, 1986

By Kazuteru Tozcwa

The oxidation of several sulfide minerals in aqueous ammoniacal solution is discussed thermodynamically. The region in which Cu(NH3)2 4+ is stable has been estimated as a function of pH and concentration of total ammonia, {[NH3) + [NH4)}. In ammonia leaching when copper in sulfides is assumed to be extracted in the form of Cu(NH3)2 which will be rapidly converted to cupric ammine, thermodynamic data predict that such minerals are oxidized readily in the following order, CuS, Cu2S, CuFeS2, ZnS, NiS, Ag2S. This agrees with investigations on ammonia leaching of sulfide minerals, reported previously. The leaching of copper sulfide concentrate has been examined experimentally. Copper in a copper sulfide concentrate, in which the main constituents were chalcopyrite and pyrite, was effective¬ly extracted. The copper extraction was affected by factors such as (1) agitation intensity, (2) oxygen partial pressure, (3) NH3/Cu molar ratio, (4) leaching temperature and (5) addition of ammonium sulfate. From the results obtained in this work, it is concluded that mass transfer of oxygen plays the most important role in ammonia leaching of copper sulfide minerals.

Jan 1, 1976

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002

By Alicia E. Ares, Carlos E. Schvezov

In the present work it was observed the nucleation and growth of grains in the equiaxed zone of metal matrix composites (MMCs) samples directionally solidified wit the presence of columnarto- equiaxed transition (CET) in the samples. In order to do so, first, it was defined the difference between the real temperature at a given instant, which it is used in the analysis, its variation and furthermore, the variation in the solid fraction with time between the beginning and the end of solidification. It was determined a growth law assuming a lineal variation of equiaxed grain radius as a function of time, and also, it was expressed a law of grain density as a function of time, considering the presence of SiC and Al2O3 particles in the matrix. Finally, the results obtained were validated with measured values of grain density at each position of the thermocouples in the equiaxed zone of the solidified samples.

Jan 1, 2015

By J. Alberto Vázquez M.

A sensor employing yttria-stabilized zirconia (YSZ) was used to determine the oxygen activity of molten copper at laboratory scale at temperatures of 1200° and 1300 dc. The reference electrode was a Ni-NiO mixture. The amount of the deoxidizing agent (CU3P) ranged from I to 3% of the mass of copper. Thermodynamic analysis of the Cu-O-P liquid system was carried out to predict the required deoxidizing agent and the final composition of the molten copper. Both results, calculated and experimental, show that the oxygen removal is more efficient at lower temperatures. The kinetics of the deoxidizing reaction is very fast in the first minutes of the treatment. A metalography analysis of rapid cooled samples show the oxygen and phosphorus distribution

Jan 1, 2003

By F. Patisson

One of the major issues with multiparticle reactors is to handle their multiscale aspect. For modeling, it usually comes to coupling a reactor model (describing the phenomena at the macroscopic scale) with a so-called grain model (simulating the behavior of a single grain or a particle). An interesting approach proposed by H.Y. Sohn (1978) is to use the law of additive reaction times in order to calculate, approximately but analytically, the reaction rate of a particle in the reactor model. Its great advantage, compared to a numerical grain model, is to drastically reduce the computation time, particularly in the case of complex reactor models. This is the approach we retained for modeling the moving bed furnace, a counter-current gas-solid reactor used in the nuclear fuel-making route for producing uranium tetrafluoride from uranium trioxide. The numerical model we developed is 2-dimensional, steady-state and based on the finite volume method. It describes solid and gas flow, convective, conductive and radiative heat transfers, and six chemical reactions involved in the process. The law of additive reaction times is used to calculate analytically the rate of the three principal gas-solid reactions at every discrete point in the reactor. We have demonstrated the validity of this approach by comparing its results with those calculated from a numerical grain model. Also detailed in the paper are the main results of the moving bed furnace model itself and the possibilities of optimizing the process revealed by the calculations.

Jan 1, 2006

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011

By Nils Eivind Kamfjord, Mari K. Næss, Gabriella M. Tranell

"In oxidative ladle refining (OLR) of silicon, the metal surface is oxidized resulting in the formation of a condensed silica fume (SiO2). In the current work, industrial measurement campaigns were performed aiming to measure the fume generation during OLR. A thorough discussion of the possible mechanisms has been included in order to improve our understanding of the Si(1)-O2(g) system.The measurement campaigns were performed at the Elkem Salten plant in Norway. In addition to fume generation from OLR, the metal temperatures and ladle purge gas amount were recorded. The results of this work suggest that fume generation during OLR results from splashing of the metal and/or oxidation of the metal surface, with oxygen transport to the metal surface being the limiting factor. Other mechanisms of SiO2 formation were investigated, however insignificant.IntroductionOne of the main environmental and economical challenges facing the metallurgical industry is fugitive emissions of both materials and energy. In the production of metallurgical grade silicon (MG-Si), refining of the silicon generally takes place through an oxidative ladle treatment (purging with an air-O2 mixture). In the refining process, exposure of silicon to air results in the formation of condensed silica fumes (SiO2) – one of the main sources of fugitive emissions in silicon production plants. The oxidation of liquid silicon, as opposed to solid silicon, has not been widely studied and described in the literature [1], thus a thorough investigation of the oxidation mechanisms, and factors affecting the oxidation reaction rate are essential in order to deal with the problem. In the current work, the rate of liquid silicon oxidation has been studied through industrial measurements of fume generation from refining adles, where the purge gas rate and composition have been varied. The results from these measurements were discussed in light of existing models describing the liquid silicon oxidation kinetics."

Jan 1, 2011

By J. Markussen

The Falconbridge Matte Leach Plant was based on leaching Ni-Cu matte with strong hydrochloric acid in rubber lined equipment. It operated from 1968 to 1983 as a precursor to Nikkelverk's present C12 Leach. The process comprised two S.X. systems. NiC12.4H20 crystallization, crystal drying, NiC12.H20 pyrohydrolysis and HC1 gas recovery. The naphtha fired fluid bed pyrohydrolyzer produced granular NiO, subsequently reduced with H2 to granular nickel for sale. The development and operation of the pyrohydrolyzer are described

Jan 1, 1991

By Guangchun Yao, Chuan Li, Hongjie Luo, Zhuokun Cao

"The expansion rate and collapse time of liquid aluminum foams are essential for the determination of operating time and quality of the resulting foam. In the present paper, liquid aluminum foams was fabricated by adding in TiH2 as blowing agent, and the variation of expansion rate with foaming time was non-contact detected by a laser distance measurer. The influence of different stabilizing agent and alloying elements was studied. The results show the fact that the fraction of stabilizing agent only perform little effects on the maximum expansion rate of liquid aluminum foams, while the influence of alloy elements are remarkable. The maximum expansion rate would increase much when Mg is added, and the liquid foam also collapse at a shorter time. Comparison was made between experimental results and mathematic calculations, which reveal the fact that it is the change of TiH2 decomposition responsible for the change.IntroductionMetal foams, combining light weight with other unique mechanical and physical properties, have gained wide interest and been developing fast during past few decades. However, manufacture of this new material is quite challenging since it involves simultaneous occurrence of gas, liquid and solid phase at high temperature [1-2].Quite some manufacture routes have been developed for manufacturing metal foams, and the structure and quality of resulting foam are remarkably improved during the last decades. However, most of the past works seems to be experiential, and because the lack of basic knowledge of foaming process, the start material is limited and the production technologies are far from reliable and reproducible.[3-4]In direct foaming process, decomposition of blowing agents, TiH2 for example, is the main force for foam expansion. The density and foam structure changes with time during the foaming process, so it is expected that foams of certain structure can be obtained by solidification of the liquid foam at a certain time [5-6]. However, the foaming process is weak in reproducibility and the influence of stabilization additives and alloying elements is unclear."

Jan 1, 2011