This study demonstrates the stabilization of Mg-3Ca foams by ex-situ addition of TiB2 particles (D50 = 8.045 μm) as effective agents to enhance foam morphology and stability. TiB2 additions (3 and 5 vol%) delayed cell coarsening and preserved higher circularity by increasing melt viscosity. While Mg-3Ca foams contracted during prolonged foaming (5–15 min), TiB2-containing foams retained and even enhanced their expansion, achieving volumes of 625 % and 652 % compared to 566 % for the base alloy. A single-film stabilization model revealed thicker and smoother films (130 μm to 323 μm) with reduced oxide accumulation in the presence of TiB2 particles, highlighting their role in enhancing foam longevity. Quasi-static compression tests indicated that higher TiB2 content introduced serrated deformation, slightly reducing energy absorption. These findings advance our understanding of particle-stabilized Mg foams, offering new opportunities for lightweight, high-performance materials

The present work aims to study the influence of hot deformation on microstructural development and flow behavior in the Al-4.8Mg-0.3Sc alloy produced by the laser powder bed fusion (LPBF) technique. Uniaxial compression tests have been conducted within a temperature regime of 200–350 ºC at a 0.01–1 s−1 strain rate using a Gleeble-3800™ thermomechanical simulator. The major results show that the flow behavior is governed mainly by strain hardening at 1 s−1 strain rate and dynamic recrystallization (DRX) at 0.1 s−1 within 250–350 ºC. The constitutive equations have been developed by employing activation energy (Q) and other material constants to forecast the influence of deformation temperature and strain rates on flow stress. Compared to other Al alloys (114–227 kJ/mol), the mean Q for hot deformation is found to be significantly higher (∼340 kJ/mol at a 0.69 true strain), indicating more stress requirement for deformation, also confirmed by the flow curves. Moreover, the processing map developed with MDMM+Poletti instability criteria is found to be appropriate compared to DMM and MDMM models. The safe workable zone is obtained in the range of 250–350 ºC/0.01–1 s−1 with a maximum power dissipation efficiency of 45.8 %. Microstructural analysis shows that recrystallization starts primarily at melt pool boundaries which formed during the LPBF process. The highest recrystallization fraction is observed for the specimen deformed at 350 ºC/0.01 s−1 (59.3 %). SEM analysis of the samples deformed at 200 ºC/0.01–1 s−1 and 250 ºC/1 s−1 depict the formation of various defects, such as voids and micro-cracks, mainly governed by the non-uniform deformation at the particle/matrix interface and due to the presence of voids/pores. A detailed investigation of Q, stress exponent (n), flow stress behavior, and constitutive equations suggests that the hot deformation is mainly governed by both dislocation climb and cross-slip mechanisms.

The present work reports the synthesis and mechanical behavior studies of Mg–3Ca alloy foams stabilized by ultrafine MgAl2O4 (spinel) particles. The MgAl2O4 particles was created in-situ in the Mg–3Ca alloy melt through the reaction of Mg, Al and O. Foaming was done by adding dolomite (CaMg(CO3)2) as blowing agent in the melt. The foaming behaviour was studied for different MgAl2O4 content in Mg–3Ca and holding times (10 and 15 min). The study reveals that the presence of MgAl2O4 significantly influences the foaming behavior of Mg–3Ca alloy resulting in equiaxed cell structure, uniform cell size distribution, higher expansion in comparison to the Mg–3Ca alloy foam which contains only MgO and CaO. An in-depth phase and microstructural analysis were performed to investigate the particles present in the gas-solid interface of the foam that contributes to foam stabilization. The quasi-static compression studies of foams exhibited better compressive strength (≈3–11 MPa) and energy absorption capacity (≈1.3–5.7 MJ/m3) in comparison to the Mg foams reported in the literature. The ductility of the Mg foams was also measured and compared with that of existing aluminium foams.

The present study aims at investigating the effect of pre-milling nickel (Ni) and aluminium (Al) powders on the sintering behaviour of NiAlFeCoCr high entropy alloys (HEA). As-milled NiAlFeCoCr HEA was prepared by mixing the Ni, Al, Fe, Co and Cr powders (in equiatomic ratio) for 10 h in a planetary ball mill. In case of pre-milled (NiAl)FeCoCr HEA, Ni and Al powders were initially milled for 5 h and this mixture was then further milled with Fe, Co and Cr powders for another 10 h. XRD, SEM-EDS, TG-DSC and Dilatometric analysis were performed for the characterization of these HEAs. The formation of FCC and BCC phases was observed in both, as-milled and pre-milled HEAs. The sintering behaviour (at 1000–1200 °C) of the HEAs was compared and observed that as-milled HEA sintered by viscous flow mechanism, which was absent in case of pre-milled HEA. An exothermic reaction observed in the as-milled HEA at 518 °C representing Ni and Al reaction, was absent in the pre-milled HEA, indicating that Ni and Al had reacted during the pre-milling process. The micro-Vickers hardness of as-milled HEA also increased from 638 ± 8.73 HV to 662 ± 12.24 HV upon pre-milling.

The paper investigates the stabilization behaviour of in-situ created, sub-micron sized MgAl2O4 (spinel) particles at various concentration in Al-11 wt%Si foams. The foam evolution (expansion, coalescence and drainage) as a function of particle concentration and foaming time was monitored in-situ using X-ray radioscopy. The foam containing higher concentration (3.4 vol%) of MgAl2O4 exhibited higher stability and expansion until solidification. Decreasing the MgAl2O4 concentration to 2.5 vol% exhibited similar foam expansion like 3.4 vol% particle-containing foam, however the stability of the former is poor due to higher drainage. The foam containing lower MgAl2O4 concentration (1.7 vol%) showed poor stability and expansion due to further increase in drainage. The 3D visualisation of MgAl2O4 particles in the gas solid interface embedded in the oxide skin was brought out by FIB tomography. TEM analysis revealed that the nano-sized MgAl2O4 particles are closely embedded in the oxide skin.

Pure Mg foams stabilized by ex-situ added CaO particles were developed in this study. Mg/xCaO foams (x = 5, 7 and 10 wt.%) exhibited uniform pore distribution, thinner yet stable pore wall cross-sections. Mg-Ca-O transition phase and MgO particles were formed at the interface of Mg-CaO, which improved the wetting of CaO particles in the Mg melt. The CaO particles, Mg-Ca-O transition phase and blocky MgO particles collectively stabilized the foam. Mg-Ca-O and MgO phases disperse along the gas-liquid interface of foams thereby preventing from wrinkling of interfaces during solidification. TEM analysis of Mg/10wt.% CaO foam powder also confirmed the formation of nano-sized (~ 200 nm) MgO particles of different morphologies. TG-DSC analysis confirmed the exothermic Mg-CaO reaction at 610 ºC, resulting in formation of Mg2Ca and MgO phases, as identified using XRD analysis. 7 wt.% CaO addition exhibited the best foam structure in terms of mean pore diameter (2.19 mm) and circularity (0.75). The lowest foam density of 0.38 g/cm3 and relative density of 21 % was achieved in case of Mg/10wt.% CaO foams.

This study aims at using Fly Ash (FA) particles as reinforcement particles in the Mg matrix and studying the thermal properties of the novel Mg-3Ca/FA composites produced via liquid processing route. About 3, 6 and 9 wt.% of FA was added to these composites. SEM micrographs of composites show the presence of Mg2Ca at grain boundaries of α-Mg, as well as micropores and agglomerates of FA particles. Mg reacts with Fly Ash constituents such as SiO2 and Al2O3 to form MgO, CaO, Mg2Si, CaMgSi and MgAl2O4, which have lower thermal conductivity than the Mg-3Ca alloy. The in situ formed phases created large number of interfaces, which increased with an increase in FA concentration in Mg composites. Decomposition of oxides increases the number of solute elements (Al, Si, etc.) in Mg that induces lattice distortions and reduction in heat flow (HF), Cp and CTE of composites. Evidently, HF, Cp and CTE of FA-reinforced composites are due to lower thermal conductivity of FA and in situ formed metal oxides when compared to that of Mg-3Ca alloy. Addition of 9 wt.% FA to the alloy reduced the Cp (at 100 °C) from 0.4033 to 0.2842 J/g °C (i.e., by 29.53%) and CTE (at 200 °C) from 26.0 to 21.9 (× 10−6)/°C (i.e., by 15.57%).

Mg-3Ca alloys with varying Zn concentration (0 to 5 wt pct) were foamed using CaCO3via liquid processing route and their compressive and energy absorption behavior were investigated. The Mg-Zn-Ca alloy foams revealed a uniform cell structure with minimum defects and improved expansion in comparison to Mg-3Ca foams without zinc. The cell wall microstructure of Mg-3Ca alloy foam revealed micro-cracks and MgO particle agglomerates at the gas-solid interfaces. Upon Zn addition, the micro-cracks were diminished to larger extent and finely MgO particles were dispersed homogenously at the gas-solid interface. Pore diameter of the foams decreased from 2.29 to 2.06 mm, while circularity improved from 0.60 to 0.72 with increasing Zn content from 0 to 5 wt pct. The peak compressive stress also improved from 1.64 to 5.09 MPa with 5 wt pct Zn addition to Mg-3Ca foam. The ductility number improved from 0.66 to 0.75 while retaining energy absorption efficiency ~ 60 pct in the plateau region. The improved mechanical properties of Mg-Zn-Ca foams are due to elimination of brittle Mg2Ca and increase in the Mg6Zn3Ca2. The reduced pore diameter, circular and equiaxed pores and crack-free interfaces in the foams were also contributed to the better mechanical properties.

The present paper investigates the stabilization of Mg-3Ca alloy and Mg-3Ca/SiC/5p composite foams with and without the addition of 0.12 wt.% beryllium. In Mg-3Ca alloy foam, Be addition has shown a significant improvement in the expansion and pore structure. Whereas, in case of Mg-3Ca/SiC/5p composite foams, the SiC particles stabilized the foam effectively, while Be addition does not show any distinguishable improvement in the foam structure. The formation of BeO and the dense coverage of SiC particles in the gas–solid interface of Mg-3Ca and Mg-3Ca/SiC/5p composite foams, respectively, are the reasons for the foam stabilization. Mg-3Ca/SiC/5p composite foam exhibited lowest foam density of 0.10 g/cm3. The quasi-static compression test shows that Mg-3Ca-0.12Be/SiC/5p composite foam containing Be exhibited lower foam density and higher normalized compressive strength. The energy absorption capacity per unit foam density in Be containing foams was also higher.

Stabilization is an essential requirement to produce closed-cell metal foams. In the melt route of foaming, usually ceramic particles are used as foam stabilizers. For the first time, the present study introduces ZrB2 particles as foam stabilizers. We demonstrate the foaming of in-situ based Al composite containing submicron ZrB2 particles. The effect of foaming temperature and holding time on the structural and mechanical properties of the foams was studied. The composites and foams were characterized using XRD, SEM/EDS, and optical scanning techniques. The mechanical properties of the foams were determined by subjecting the foams to a quasi-static compression test. Submicron ZrB2 particles present in the cell wall and at the gas-solid interface promoted foam stability. All the foams exhibited a good cellular structure with high expansion. Among all the foams, the foams prepared at 680 °C with a holding time of 120 s exhibited the smallest cell size and the best mechanical properties. The structural and mechanical properties of the Al–5ZrB2 foams were found to be comparable to conventional foams.

The present work is the first ever study where the influence of beryllium (Be) addition on the stability of Mg alloy foam was investigated. Mg-3Ca alloy foams were produced by the liquid processing route with and without Be micro-addition. CaCO3 was used as a blowing agent. Mg-3Ca alloy foam without Be resulted in stable foam but exhibited low expansion with poor foam structure. Be addition significantly increased foam expansion and improved their structure. The expansion and the structure of the Mg foams obtained are comparable with that of commercially available aluminum foams. The XPS analysis confirmed the presence of BeO at the gas–solid interface of Mg foam. Be stabilizes the gas–solid interface of the foam by forming a smooth and crack-free surface of BeO layer which prevents the continuous oxidation of liquid foam and also minimizes the loss of blowing gas thereby enhancing the stability of Mg-3Ca alloy foams.

The present work reports on foaming of magnesium alloys and composites using MgCO3 as the blowing agent. Foaming was done via the molten metal route by direct addition of MgCO3 in molten Mg. The alloys and composites required for foaming were prepared by varying the concentration of aluminum (10 to 30 wt pct) and calcium (0 and 2 wt pct) in Mg. SiC of 10-µm size and about 10 to 20 vol pct was added as reinforcement particles in the composite. The liquidus temperature of the alloys and composites, the decomposition behavior of MgCO3, and the intrinsic oxides that formed in the melt have a significant effect on the structure of the foams. Mg alloys and composites with 30 wt pct Al showed better foaming behavior with higher expansion, lower density, good cell structure, and uniform cell size distribution due to the smaller difference between their liquidus temperature and the decomposition temperature of MgCO3. The addition of 2 wt pct Ca showed a significant effect on foaming, and the MgO and MgAl2O4 (spinel) particles formed in situ in the molten Mg during foaming acted as the stabilizing agents.

In this study, it was shown that aluminum powder can be used as stabilizing particles for the fabrication of aluminum foams by melt route. When Al powder was mixed with the TiH2 before adding into the melt, it also acted as dispersing agent for the TiH2 thus further improving the structure of the foams. Stirring during powder mixing also contributed towards foam stability by introducing oxides into the melt. The oxides were examined using SEM/EDS and oxygen analyzer.

The paper aims to investigate standalone FeCoCrNi2Al, FeCoCrNiAl0.3, FeCoNiAlTi0.4 and NiCoCrAlSi high entropy alloys (HEA) as a possible bond coat material for thermal barrier coating (TBC) system. For this high entropy alloys prepared by mechanical activated synthesis (MAS) were densified by spark plasma sintering (SPS). MAS HEAs were investigated for phase formation, melting temperature and coefficient of thermal expansion by X-ray diffractometer (XRD), Differential scanning calorimetry (DSC) and Dilatometer respectively. Isothermal oxidation of sintered samples was carried out at 1050 °C for a period of 5, 25, 50, 100, 200 and 300 h in the air. The formation and growth of thermally grown oxides (TGO) were investigated by Raman spectroscopy, X-Ray Diffraction, and Scanning electron microscopy (SEM). The oxidation study shows that FeCoCrNi2Al and FeCoNiAlTi0.4 HEA follow parabolic rate weight gain due to the formation of TGO enriched in Al2O3. Discontinuous weight changes due to the formation of CoAl2O4, NiCrFeO4, and Cr2O3 phases were observed in FeCoCrNiAl0.3 HEA. TGO enriched in Al2O3 and NiAl2O4 were observed in NiCoCrAlSi HEA, whereas FeCoNiAlTi0.4 HEA shows the formation of TGO enriched in Al2O3, NiAl2O4, Ti2O3, and Al2O5Ti. Increase in coefficient of thermal expansion (CTE) with increasing temperature is observed for FeCoCrNi2Al and FeCoNiAlTi0.4 HEA. FeCoCrNi2Al HEA showing average CTE of 15.16 ± 0.25 × 10−6/K, good mechanical properties, and containing α-alumina TGO layer, makes it a potential candidate for a bond coat material.

Aluminium foam is most commonly used in automobiles, so a closed-cell foam is going to be prepared. This is prepared by the powder metallurgy process using aluminium in addition to Copper and Magnesium, along with Titanium Hydride as a blowing agent. The composition of the powder used vary with weight%, Aluminium of purity 99.7%, Copper of purity 99.8%, Mg of purity 98.3% along with this TiH2 is used as a blowing agent. Copper is used in this method because it has higher melting temperature and higher strength, and also to add strength to aluminium while compacting. The composition of Al-Mg-Cu produces foam with properties of corrosion resistance, and also reduce the weight of the foam. Since Mg gives better result than the Cu, Mg is used as an alloying element because it can increase the oxidation rate, improve the structure of the pore developed in foam, can produce less coarse and more homogeneous foams, and also obtain the maximum expansion of the foam. Thus by varying the parameters like varying the composition of the powder, temperature, time and the pressure given during compaction we will be able obtain a better result for producing a good precursor.

Aluminium alloy foams are created by injecting air into liquid alloys containing non-metallic particles. In addition to an alloy containing the usual SiC particles, other types of metal/particle composites are studied, which are created by in situ reactions in the melts: two fluoride salts react and form TiB2 particles, and Ca addition or addition of CuO and SiO2 gives rise to the formation of various oxides and spinel particles. Injecting air into the molten composites through two different steel cannulas leads to the formation of first bubbles and then foam. The entire process is monitored in situ by X-ray radioscopy. The goal is not only to understand how and what kind of particles stabilise gas injected foams better, but also to reduce the fraction of added particles, which could improve mechanical properties, solve recycling issues and reduce production costs. All the observed composites are shown to have the potential to be processed to metallic foam. Melts containing TiB2 particles are found to perform as well as those containing SiC even at lower volume fractions. Oxidation of alloy melts promoted by Ca addition gives rise to melts that exhibit good foamability. Melts oxidised by CuO and SiO2 addition show partial stability. Mg is found to be a required alloying element to create stable foams. Smaller bubbles can be produced using smaller injector needle openings. By reducing bubble size and using new variants of in situ generated particles, more stable foams can be achieved with a lower number density of stabilising particles.

Closed-cell foams were produced from re-melted aluminum alloy scrap that contained 0.13 wt pct Mg magnesium in the as-received state and higher levels after adding 1, 2, or 5 wt pct Mg. The excess Mg gave rise to the fragmentation of long oxide filaments present in the scrap alloy into smaller filaments and improved its distribution and wetting by the Al matrix. Foaming the re-melted scrap alloy containing 1, 2, and 5 wt pct Mg excess showed stability and good expansion in comparison to the scrap alloy containing 0.13 wt pct Mg only, but the cells became non-equiaxed when the Mg concentration was high (≥2 wt pct excess) due to cell wall rupture during solidification. Compressibility and energy absorption behavior were studied for scrap alloy foams containing 1 wt pct Mg excess, which is the optimum level to obtain good expansion, stability, and uniform cell size. Foams with densities in the range of 0.2 to 0.4 g cm−1 produced by holding at the foaming temperature for different times were used for the investigation. A uniform cell structure led to flatter stress plateaus, higher energy absorption efficiencies, and reduced “knockdown” in strength compared with commercial foams made by gas bubbling. The mechanical performance found is comparable to that of commercial foams made by a similar method but the expected costs are lower.

Metallic foams have now reached the maturity of development in terms of process stability, materials properties and costs required for industrial applications. The fine-tuning of the manufacturing process carried out in the past few years has been responsible for this success. Nowadays, Al foam panels as large as 2.5 m × 1.5 m in area and having a uniform pore structure are commercially available. In parallel to this development, new processing routes are being explored, including foaming with novel blowing agents, foaming by application of under-pressure, foaming of scrap and of other metals such as magnesium. Some of the steps of these developments are reviewed.

The expansion and stability of foams made from remelted aluminium alloy scrap has been studied. Foams made from scrap alloy contain oxide bi-films introduced from the swarf (machining chips and turnings) of LM26 alloy and these oxides act as stabilizing agents. The wettability of the oxides and hence the stabilisation is studied by varying the addition of Mg (0 to 2 wt.%) in the alloy. The viscosity of the melts with and without Mg addition is measured and correlated with foam expansion and stability. A detailed microstructural analysis of the base alloy and foam cell wall was conducted to obtain an understanding of the stabilisation behaviour of oxides.

Aluminium alloy foams are created by injecting gas containing different levels of oxygen (from 蠐1 ppm to 21%) into melts stabilised with SiC or TiB<inf>2</inf> particles. Individual liquid aluminium alloy films meant to represent the films in a foam are produced of the same materials. For foams and films, the oxygen concentration of the atmosphere is controlled. Synchrotron X-ray radioscopy on liquid films is applied to track the movements of the particles within and to observe how they flow, pile up and form clusters. Experiments on aluminium foams show that only when the injected gas and the surrounding atmosphere contain oxygen foams can be expanded continuously. In contrast, if foaming is carried out by injecting argon into the melt and the Ar atmosphere is free of oxygen no stable foams can be created, even if the melt contains 20 vol.% SiC particles. Both film and foam surfaces are analysed ex-situ by energy-filtered TEM and SEM. It is found that oxide layers form, cover the particles and push them into the metal. A high oxygen content in combination with Mg in the alloy promotes this process. It is concluded that not only particles are required to allow for foaming, but also the formation of an oxide skin is necessary and the combination of both are the basis of film and foam stabilisation.

The expansion and stability of foams made from remelted aluminium alloy scrap has been studied. Foams made from scrap alloy contain oxide bi-films introduced from the swarf (machining chips and turnings) of LM26 alloy and these oxides act as stabilizing agents. The wettability of the oxides and hence the stabilisation is studied by varying the addition of Mg (0 to 2 wt.%) in the alloy. The viscosity of the melts with and without Mg addition is measured and correlated with foam expansion and stability. A detailed microstructural analysis of the base alloy and foam cell wall was conducted to obtain an understanding of the stabilisation behaviour of oxides.

The present study is based on the idea of understanding the rupture of films in metal foams by studying free standing metallic films as a model system. Liquid dynamics, the velocity of the rupturing material as well as the behaviour of ceramic particles inside the melt were analysed optically ex situ and by synchrotron X-ray radiography in situ. It was found that the resistance of films to rupture is mainly based on the interaction between solid particles and an immobile oxide skin, the formation of which depends on the oxygen content of the surrounding atmosphere and the presence of magnesium. This journal is © the Partner Organisations 2014.

Complex liquid structures such as metallic foams were produced in a furnace that allowed in situ X-ray monitoring of the evolution of the structure and distribution of the liquid in the foam. The experiments were carried out during parabolic flights which provided varying levels of gravity. The evolution of the characteristic liquid fraction profiles due to gravity induced drainage was measured and analysed in terms of the foam drainage equation, obtaining viscosity and surface tension by fitting solutions of the equation to the experimental data. The surface tension of the melt in the foam was decreased up to 40%. Effective viscosities of up to 139 times the viscosity of a pure bulk melt were observed. These effects could be attributed to the smaller influence of solid particles dispersed in the melt and the larger influence of the complex foam structure. © 2014 the Partner Organisations.

We developed a novel process for foaming aluminum and its alloys without using a blowing agent. The process involves a designated apparatus in which molten aluminum and its alloys are first foamed under reduced pressure and then solidified quickly. Foaming was done for pure aluminum (99.99 pct) and AlMg5 alloy not containing stabilizing particles and AlMg5 and AlSi9Mg5 alloys containing 5 vol pct SiO2 particles. We discuss the foaming mechanism and develop a model for estimating the porosity that can be achieved in this process. The nucleation of pores in foams is also discussed. © 2012 The Minerals, Metals & Materials Society and ASM International.

Liquid metallic alloys with and without stabilizing particles such as TiB2 or SiC were processed to single films or artificial single Plateau borders to clarify the stabilization mechanisms of metallic foams based on the same melts. First, isolated single films were pulled out of a liquid metal by using circular wire frames of various sizes. Modified wire frame structures comprising double or quadruple parallel frames were then used to create artificial metallic Plateau borders. Drainage in single metallic films between two Plateau borders was studied by cutting films vertically and analysing their cross sections. Particle movement in liquid films was observed in-situ via synchrotron X-ray radioscopy. It was found that Mg-free liquid metallic alloys containing stabilising particles are less stable and rupture immediately because of unhindered drainage. In contrast, films made of AlSi9Mg0.6 alloy containing TiB2 or SiC are stable for long holding times. Our study shows that the complexity of drainage and evolution of Plateau borders in true metal foams can be studied by using a simple model system based on a single metallic film between two artificial Plateau borders. © 2013 Elsevier B.V.

Aluminum alloys made from machining chips that have been heat treated and re-melted, have been successfully foamed (after the addition of TiH2) using processes analogous to both the "Alporas" and "Formgrip" methods. The high oxygen contents associated with the swarf (0.11 wt% for the as-received material, increasing to >0.5 wt% after conditioning) results in large fractions of both clustered and dispersed oxide films in the melt. It is these films that enhance the "foamability" of this material. Through additional alloying with Mg and holding in the liquid state to allow reaction to take place, fragmentation and wetting of the oxides occurs and foams with low densities (<0.3 g cm-3), good pore structures, and good stability were obtained. The use of scrap material, without costly or embrittling additives, offers a low cost route to the manufacture of high quality foams. Aluminum machining chips have been successfully foamed using processes analogous to both the "Alporas" and "Formgrip" methods. The chips provide large fractions of both clustered and dispersed oxide films to the liquid, which enhances its "foamability." Through additional alloying with Mg and "melt conditioning," fragmentation and wetting of the oxides occurs and foams with low densities, good pore structures, and good stability are obtained. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of facets of particles is a common problem. In this paper an algorithm is presented which allows automated quantitative 3D analysis of facets of many particles within tomographic datasets. The algorithm is based on the analysis of probability distributions of the orientations of triangle normals of mesh representations. The result consists of lists containing number of detected facets, their size, global orientation and the interplanar angles between facets for each analyzed particle. Characterization of each particle according to any of these facet properties is then possible, e.g. statistics about different crystal shapes or removal of particles that do not show significant faceting. Analyses of a 3D dataset obtained by focused ion beam (FIB) tomography of a sample containing spinel particles are presented. © 2012 Elsevier B.V.

Strontium-modified Al-15 wt%Si casting alloys were investigated after 5 and 60 min of melt holding. The eutectic microstructures were studied using complementary methods at different length scales: focused ion beam-energy selective backscattered tomography, transmission electron microscopy and 3D atom probe. Whereas the samples after 5 min of melt holding show that the structure of eutectic Si changes into a fine fibrous morphology, the increase of prolonged melt holding (60 min) leads to the loss of Sr within the alloy with an evolution of an unmodified eutectic microstructure displaying coarse interconnected Si plates. Strontium was found at the Al/Si eutectic interfaces on the side of the eutectic Al region, measured by 3D atom probe. The new results obtained using 3D atom probe shed light on the location of Sr within the Al-Si eutectic microstructure. © 2010 Elsevier B.V.

A novel foamable aluminum alloy has been developed. It contains sub-micron-sized MgAl2O4 (spinel) particles that are generated in situ by a reaction of SiO2 with a molten Al-Mg alloy. The study involves an optimization of parameters such as Mg concentration, SiO2 particles size, and reaction time and shows that a composite containing MgAl2O4 particles as chief reinforcement in the matrix leads to effective foaming. Composites containing large sized transition phases and particle agglomerates in the matrix yield poor foam structure. The best foamable composite obtained contained 3.4 vol. pct of ultrafine (80 nm to 1 μm) MgAl2O4 particles uniformly distributed in an Al-Si alloy matrix. The corresponding metal foam contained 75 pct porosity and exhibited a uniform distribution of cells. © The Minerals, Metals & Materials Society and ASM International 2011.

The effect of TiAl3 particle size and distribution on their settling and dissolution behaviour in molten aluminium during grain refinement has been studied. For this purpose Al-5Ti master alloys containing blocky TiAl3 particles of different size and distribution are synthesised at reaction temperatures 750, 800 and 850 °C for 60 min and used for grain refinement. The extent of fading and the recovery due to stirring is calculated from the measured grain size and used to judge the dissolution and settling behaviour of TiAl3 in molten Al, which is greatly attributed to its size and distribution in Al-5Ti master alloy. Fine TiAl3 particle dissolve faster in the melt and cause fading. Larger size TiAl3 particles exist for longer time in molten Al and act as a nucleating site even when added in hypoperitectic concentration (0.05 wt% Ti). © 2010 Springer Science+Business Media, LLC.

An investigation into the effect of ternary alloying element additions such as copper, magnesium, manganese, zinc, and nickel on pore formation in cast Al-12.6-wt pct Si eutectic alloy by employing a novel pore characterization technique is reported here. In this approach, the low-pressure testing method was combined with the metal foam manufacturing technique of intentionally adding TiH2, which enhances hydrogen pore formation and offers a method to distinguish the effect of individual alloying elements on hydrogen porosity formation. © The Minerals, Metals & Materials Society and ASM International 2010.

The settling behaviour of heterogeneous nucleating particles such as TiAl3, TiB2, AlB2 and TiC in liquid Al has been studied through vertical sectioning experiments. The experimental results obtained were correlated with the settling rate of the particles calculated using the Stokes' law. The TiB2 and TiC particles show larger settling tendency among all particles studied. The overall settling behaviour of the particles is largely influenced by their size distribution in their respective master alloys, their agglomeration and dissolution behaviour in the liquid Al. © 2010 W. S. Maney & Son Ltd.

The grain refining response of LM25 (Al-7Si-0.35Mg) alloy has been studied with the newly made Al-5Ti-0.8C and Al-5Ti-1.2C master alloys which have been successfully prepared in the laboratory by reaction of K2TiF6 salt and graphite powder with Al. The results have been compared with the grain refining efficiency of Al-3B, Al-1Ti-3B and Al-5Ti-1B master alloys on LM25 alloy at different addition levels. The results show that the grain refining efficiency of even lowest addition level (0.1 wt.%) of both Al-5Ti-0.8C and Al-5Ti-1.2C master alloys are equivalent to the 1.0 wt.% addition levels of Al-1Ti-3B and better than 1.0 wt.% of Al-3B master alloy. At higher addition levels of Al-5Ti-0.8C and Al-5Ti-1.2C master alloys exhibits fading in grain structure on longer holding due to agglomeration of TiC particles and poisoning of Si. © 2008 Elsevier B.V. All rights reserved.

Liquid metals are mostly made foamable by Ca additions followed by a thickening period. There is a need for an additive that can be easily admixed to an aluminium alloy melt and makes this melt foamable. We have selected aluminium-based grain refiner composites to test their foamability. TiB 2, TiC or TiAl3 particles were produced in the melt by flux-assisted melting using fluoride salts. The particle size was kept below 1 μm for TiB2 and TiC and around 10 μm for TiAl3. The composites were heated to above their melting point (700°C) and were then foamed by either the addition of TiH2 or by injecting gases into the melt directly. Foams were successfully produced using TiB2 and TiC particles, while TiAl3 did not lead to any foam. Foam stability increased from TiB2 to TiC. Ex-situ characterisation of the foams by SEM showed that the particles segregate to the surfaces of the cell walls and lead to almost dense coverages there. Even after dilution of the initial composite a significant amount of foam can be still produced, indicating that these composites are suitable foam stabilizing additive for aluminium alloys and that foams based on small volume fractions of non-metallic additives can be produced.

The present paper deals with a novel experimental technique to study liquid metal foam stability. This method is based on making single films from liquid Al and Al alloys with and without stabilizing particles and to show how foams stability could be studied on a simplified system such as a single film instead of having to deal with a multitude of different structural elements present in a foam. It is found that merely weakly stable films can be made from commercially pure Al and no stable films from Al-Si alloys which do not contain any particles. In contrast, thin stable films without rupture could be made from aluminium alloy containing particles such as SiC and TiB2. Significant thinning of film is observed when the particle concentration decreases in the melt.

The present work reports on the foaming of liquid aluminium containing TiB2, TiC or TiAl3 particles (4-11.5 vol.%) which were prepared in-situ by flux-assisted melting using fluorides. This procedure was in analogy to the production of composites containing grain refining particles. The particle size was kept below 1 μm for TiB2 and TiC and around 10 μm for TiAl3. Foams were successfully produced using TiB 2 and TiC particles and thus it could be demonstrated for the first time that metal foams can be stabilised by sub-micrometre particles. The influence on foam stability of alloying with Si and dilution of the melt with pure Al was studied in addition. Microstructural analysis of the foams showed that the particles segregate to the surfaces of cell walls leading to an almost dense coverage, thus helping in stabilising the foams.

In the present paper the authors studied isolated metallic films made from the same material used for making metallic foams, and then characterised their properties. Metal films were made from a liquid aluminium alloy reinforced with ceramic particles of known concentration. Melts without such particles were also investigated. It is shown that stable films could not be made from Al-Si alloy having no particles, and just extremely thin and fragile films could be made from commercially-pure Al. In contrast, aluminium alloys containing particles such as SiC and TiB2 allowed pulling thin, stable films, which did not rupture. Significant thinning of films was observed when the particle concentration in the melt decreased. By in situ X-ray monitoring of liquid films during pulling, film thickness and drainage effects within the liquid film could be studied. The morphology and microstructure of films was characterised after solidification. Our work shows that the question of how foams are stabilised can be studied using a simplified system such as a film, instead of having to deal with the multitude of different structural elements present in a foam. © the Owner Societies.

The present paper reviews the grain refinement experiments conducted in the author's laboratory to understand the poisoning and fading phenomena in the grain refinement of Al and its alloys. The dissolution and settling behavior of TiAl3, TiB2, and TiC particles in Al melt, which cause fading during grain refinement, has been studied in detail. The poisoning effect of the alloying elements such as Cr, Zr and high level of Si with Al-5Ti-1B master alloy as grain refiner has been demonstrated. Boron rich master alloys such Al-3B and Al-1Ti-3B and newly developed Al-Ti-C master alloys are found to be more effective grain refiners for Al-Si alloys compared to the conventional Al-5Ti-1B master alloys.

Al-5Ti-0.8C and Al-5Ti-1.2C master alloys have been successfully prepared by reaction of K2TiF6 salt and graphite powder with molten Al. While the Al-5Ti-0.8C consists of some TiAl3 particles in addition to TiC particles in the Al matrix, the Al-5Ti-1.2C master alloy revealed the presence of only TiC particles. The grain refining efficiency of these two master alloys has been compared with that of the conventional Al-5Ti-1B master alloy on Al and Al-7Si alloy at different addition levels. Al-5Ti-1.2C master alloy was found to be the most efficient grain refiner for Al amongst the grain refiners studied. Even in case of Al-7Si alloy, the Al-5Ti-0.8C and Al-5Ti-1.2C master alloys performed better than conventional Al-5Ti-1B master alloy. However, the Al-5Ti-1.2C master alloy shows poor response to grain refinement in Al-7Si alloy at higher addition levels than the Al-5Ti-0.8C master alloy, indicating poisoning. © 2005 Elsevier B.V. All rights reserved.

Catalase-like activity of the metal complexes of various crosslinked polystyrene-supported Schiff bases were carried out and correlated with the nature and degree of crosslinking in the polymer support. Polystyrenes with 2-20 mol % ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol dimethacrylate (BDDMA) and 1,6-hexanediol diacrylate (HDODA) were used as polymer supports, functions of diethylenetriamine and salicylaldehyde were incorporated to the chloromethylpolystyrene by polymer analogous reactions and complexed with Fe(II), Fe(III), Co(II), Ni(II), and Cu(II) ions. The metal uptake decreased in the order: Cu(II) > Co(II) > Ni(II) > Fe(III) > Fe(II), and extent of metal uptake by the various crosslinked system varied with the nature and degree of the crosslinking agent. The polymeric ligands and the metal complexes were characterized by various analytical techniques. The catalytic activities of these metal complexes were investigated towards the decomposition reaction of hydrogen peroxide. Generally among the various metal complexes, the catalytic activities decreased in the order: Co(II) > Cu(II) > Ni(II) > Fe(III) ≅ Fe(II). With increasing rigidity of the crosslinking agent their catalytic activity also decreased. Of the various crosslinked systems, the catalytic activity decreased in the order: HDODA- > BDDMA- > EGDMA-crosslinked system. Also, the catalytic activity is higher for low crosslinked systems and decreased further with increasing degree of crosslinking. © 2004 Wiley Periodicals, Inc.

A high swelling resin, CLPSER has been developed and utilized for the solid phase synthesis of Pardaxin, which is an 18-residue peptide. The resin was characterized by gel phase 13C NMR, IR and SEM. The utility of the new polymer support in polypeptide synthesis was further established by the comparative synthesis of pardaxin with commercially available Merrifield resin. The MALDI TOF MS, amino acid analysis and the HPLC revealed the superior quality of CLPSER.