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Metal matrix syntactic foams (MMSF) are foam composites obtained by filling hollow and/or porous particles into a metal matrix. MMSF are promising materials in defense, aerospace, automotive, marine and engineering applications. Mechanical and physical properties of MMSF can be tailored to reach better structural and/or functional behaviors by fitting processing and tailoring parameters. Some of these parameters are: reinforcement size, volume fraction, distribution of reinforcements and chemical composition. Three techniques are available to manufacture MMSF: Stir casting/vortex method (SC), powder metallurgy (P/M) and infiltration routes. Infiltration process is by far the main employed for making MMSF, it allows a large range of reinforcement (30 vol % to 78 vol %) and offers great advantages compared to other techniques. This paper reviews infiltration routes used to date, their advantages and drawbacks, the main processing parameters of each route, and a relation of representative studies developed to date on the synthesizing of MMSF by molten infiltration processes.

In this paper, the sound absorption properties of aluminum sponges manufactured by infiltration process have been studied. The results show that the sound absorption factor α changes in function of pore size. Additionally, the sound absorption factor α was sensitive to the frequency range measured and it was depending of the thickness sample. It was found that the interconnected porosity plays an important role increasing the sound absorption properties of the aluminum sponges studied.

Aluminium foams can be manufactured by two main methods: casting and powder metallurgy. When the latter route is used, a foaming agent (usually TiH2) is mixed with the aluminium or aluminium alloy powders, followed by powder mixture consolidation (usually hot extrusion) into a precursor and finally its foaming treatment. In this research, two calcium carbonate powders were used as foaming agents on an Al–Mg–Si (AA6061) alloy. Their different characteristics (particle size and chemical composition) modified the manufacturing process to achieve the final foam. AA6061 powders were then mixed with 10% calcium carbonate and, after cold isostatic pressing into green cylinders, hot extruded at different temperatures (475–545 °C). The foaming treatment was carried out in a furnace preheated to 750 °C using several heating times. The density changed from 2.03 to 2.10 g/cm3 after cold isostatic pressing to 2.64–2.69 g/cm3 in precursor materials obtained by hot extrusion. Foaming behaviour depends on the carbonate powder as well as the extrusion temperature. Thus, natural carbonate powder (white marble) produces a foam density close to 0.65 g/cm3 after a shorter time than when chemical carbonate is used. The foam structure showed a low degree of aluminium draining, no wall cell cracks and a good fine cell size distribution. Compressive strength of 6.11 MPa and 1.8 kJ/m3 of energy absorption were obtained on AA6061 foams with a density between 0.53 and 0.56 g/cm3.

The decomposition of constituents of slates under non-oxidizing atmosphere leads to the manufacturing of foams. Thus die pressing at 80MPa of slates powders (particle size La descomposición de los componentes de la Pizarra durante su calentamiento en condiciones no oxidantes conduce a la obtención de espumas. Así, mediante la compactación en matriz a 80MPa de polvos de Pizarra de menos de 80 μm de tamaño de partícula y con adición de un aglomerante, se obtiene una densidad en verde próxima a 1,8 g/cm3. El calentamiento de estos compactos en atmósfera de N2-5% H2 permite alcanzar densidades de 2,2 g/cm3 a 1100ºC , mientras que a 1150ºC la espumación del compacto conduce a densidades inferiores a 0,4 g/cm3. La adición de Clínquer de cemento Portland (5% y 10% en peso) modifica la densidad de la espuma a 1150ºC , teniendo que elevarse la temperatura de sinterización a 1175 ºC para alcanzarse espumas con densidades próximas a 0,4 g/cm3 con un 10% de Clínquer. Estas espumas con Clínquer presentan un elevado tamaño de poro, así como una resistencia a compresión en el intervalo de resistencias de los vidrios espumados: 0,4-1,5MPa.

Manufacturing of metal matrix composites (MMCs) through powder metallurgy route and their characterisation are the objects of the present work. Thus a light alloy reinforced with 5% of ceramics is obtained after attrition milling of mixed powders, die pressing, lubrication of compacts and hot extrusion into 10 mm diameter bars. Since 7xxx series of aluminium alloys show high mechanical properties, AA7015 alloy was chosen as metallic matrix and B 4 C, TiB 2 and Si 3 N 4 ceramics were added. After process optimisation, the microstructure of these materials shows a uniform distribution of ceramics in the aluminium alloy matrix. Physical properties like density, conductivity and coefficient of linear dilatation were determined on extruded MMCs samples. Hardness and tensile strength properties on machined samples according to ISO 2740 standard were evaluated. Also wear behaviour using a pin-on disk test was studied, within a microstructure study, which was carried out using optical and scanning electron microscopy.

Manufacturing and characterization of bearing materials is the object of the present work. Thus, graphite particles are added to an aluminium matrix as lubricant. It was added as nickel coated graphite in order to avoid a strength decreasing. Mixing of powders following by cold compaction and hot extrusion was the manufacturing way. Extruded materials showed good graphite distribution into the aluminium matrix, with densities between 3.11 to 3.75 g/cm3 as a function of the nickel/graphite content. Hardness and radial crushing strength decrease when graphite content is increased. On the contrary, friction properties are improved with the graphite content because it decreases friction coefficient and wear. Diffusion heat treatment on extruded materials improves furthermore these friction properties but it decreases the radial crushing strength.El objeto de este trabajo es la obtención y caracterización de materiales compuestos (MMC´s) para la fabricación de cojinetes para fricción en seco. Así se incorpora a una matriz de aluminio, partículas de grafito para actuar como lubricante si bien en forma de grafito recubierto de níquel para disminuir la perdida de resistencia que presentan estos materiales. La fabricación de estos materiales se realizó mediante compactación de las mezclas de polvos en matriz y su extrusión en caliente. Los materiales obtenidos presentaron una buena distribución del grafito en la matriz de aluminio, con densidades entre 3.11 g/cm3 y 3.75 g/cm3 según el contenido de níquel/grafito. La dureza y la resistencia al aplastamiento radial disminuyen al aumentar el contenido en grafito. No obstante, un mayor contenido en grafito si mejora las propiedades a fricción del material, disminuyendo el desgaste ocasionado y reduciendo el coeficiente de fricción. El tratamiento térmico de difusión de los materiales extruidos mejora sus propiedades de fricción si bien disminuye su resistencia al aplastamiento radial.

On the present work the objective is to manufacture a AA2014+10 vol-% Intermetallic (NbAl3 or FeAl2 ) metal matrix composites. Since Powder Metallurgy route was chosen, the powder mixtures of metallic powders which forms AA2014 alloy and intermetallic powders were obtained by mechanical alloying. Powder mixtures were cold die pressing and green samples were hot extruded. As result of this intermetallic addition, mechanical properties of AA2014 alloy are improved and a tensile strength of 516 MPa on AA2014+NbAl3 and 465MPa on AA2014+FeAl2 within an elongation close to 2% on both metal matrix composite materials are reached.El objeto del presente trabajo es la obtención de los materiales compuestos AA2014 +10 vol-% NbAl3 o FeAl2. Para ello se realizó la mezcla inicial de los polvos metálicos que constituyen la aleación AA2014 y de los polvos de estos intermetálicos seguido de su aleación. Las mezclas obtenidas se compactaron en frío y los compactos en verde se extruyeron en caliente. Como resultado de la adición de los intermetálicos se mejoran las propiedades mecánicas de la aleación AA2014, alcanzándose resistencias a tracción de 516 MPa para el AA2014+NbAl3 y de 465MPa para el AA2014+FeAl2, con un alargamiento próximo al 2.0% en ambos materiales compuestos de matriz metálica.

The influence of several heat treatments on the mechanical and physical properties of three different sintered Ni-Cu-Mo alloyed steels are evaluated. The heat treatments carried out were quenching and tempering at different temperatures. The raw material studied was a Fe-Mo prealloyed powder with an 1.5% Mo content.Se estudia la influencia que distintos estados de tratamiento térmico ejercen sobre las propiedades mecánicas y físicas de tres aceros aleados con cobre, níquel y molibdeno sinterizados. Los tratamientos térmicos realizados consisten en temple y revenido a distintas temperaturas. El material de partida utilizado para conseguir la aleación de molibdeno ha sido un polvo prealeado de Fe-1,5% Mo.

Sintered molybdenum-, copper-, nickel- alloyed steels, have been studied through the influence of the Chemical composition on different mechanical and physical properties. In all the studied steels, a constant percentage of carbon has been used, as well Fe-Mo prealloyed powders, with a 1,5% Mo content. Selected sintering conditions were close to those used in the P/M industry, potential consumer of the studied steels.Se estudian los aceros aleados sinterizados con molibdeno, cobre, níquel y grafito, a partir de la influencia de su composición sobre distintas propiedades mecánicas y físicas. En todos los aceros, se utilizó una composición de carbono constante, así como polvos prealeados de Fe-Mo, con 1,5% Mo. Las condiciones de sinterización elegidas han sido las más próximas a las utilizadas en la industria pulvimetalúrgica, que es el usuario potencial de los materiales estudiados.

To date little work has been done on powder metallurgical duplex austenitic-ferritic stainless steels. In the present work the manufacture of this type of steel from prealloyed and mixed powders is studied together with the possibility of obtaining duplex compositions of other than 50% ferrite-50% austenite. Mechanical properties, microstructure, and dimensional behaviour of the sintered powders are investigated. Studies on powders sintered at the higher experimental sintering temperature of 1250°C show that there is little difference found between the properties of materials obtained from prealloyed and mixed powders when they contain the same percentages of ferrite and austenite. The strength of duplex stainless steel derived from mixed powders increases with the ferrite content and the dimensional change on sintering is found to be lower for mixed powders than for the prealloyed material. It has been found, however, that a low sintering temperature (1120°C) can cause heterogeneous microstructur...

The present study determines and compares the physical and mechanical properties of sintered 1·5 wt-%Mo steels as a function of the carbon content, the type of raw material (prealloyed powder or elemental powder mixture), and the heat treatment used after sintering. The steels were mixed and pressed under the same conditions and the sintering conditions approximated to those normally used in the industry. PM/0620

In the present work, clinker Portland has been used, not as a component of cements manufacture, but like a raw material for making structural ceramics. The manufacturing process for this material includes blending for homogenization followed by cold isostatic pressing and sintering. The sinterability of clinker Portland has been evaluated. Also mechanical properties, microstructure and mechanical reliability through the Weibull modulus, were evaluated in all of the sintered materials.

In the present work we have studied the feasibility of Powder Metallurgy in order to obtain structural ceramics from residual fly ashes powders. Characterization of powders has been carried out followed with the manufacturion of a structural ceramic through poeder compacting and sintering. Some physical and mechanical properties as density, dimensional changes and transverse rupture strength of the obtained materials were evaluated.En el presente trabajo se ha investigado la posible utilización de un residuo de las centrales térmicas de carbón de hulla, como son las cenizas volantes silicoaluminosas (clase F) ocasionadas en los procesos de combustión, como materia prima para la fabricación de materiales cerámicos estructurales.De este modo se ha procedido a la caracterización del polvo de partida para la posterior fabricación de un material cerámico mediante compactación y sinterización. Por último, se procedió a la evaluación de diversas propiedades físicas y mecánicas como son la densidad, variación dimensional, absorción de agua y resistencia a flexión de los materiales obtenidos.

In this research work we have studied the efficiency of using an advanced techniqhe, as mechanical alloying, on the metal matrix composites fabrication process by powder metallurgy. From the analysis of several composites, based on M2 high speed steel reinforced with WC, we inferred that mechanical alloying is an effectve method to manufacture these materials, and they present higher mechanical properties than high alloy steels used in structural applications.En este trabajo se estudia la eficacia del empleo de la aleación mecánica, en el proceso de fabricación de materiales compuestos de matriz metálica (base acero rápido M2) mediante técnicas pulvimetalúrgicas. Del análisis de los materiales obtenidos, acero rápido M2 reforzado con WC, se deduce que la aleación mecánica resulta ser un método eficaz para la fabricación de estos compuestos, ya que se alcanzan unas excelentes propiedades mecánicas, que superan ampliamente a las que presentan los mismos aceros reforzados con carburos mediante procesos pulvimetalúrgicos convencionales.

La transformación de los residuos de pizarra de techar en materias primas no tradicionales de la industria cerámica, es el objetivo del presente trabajo. Sin la adición de agentes espumantes, mediante la alteración que sufren los componentes de la pizarra cuando la misma es sometida a un calentamiento en atmósfera no oxidante, se han alcanzado espumas de poro cerrado o cerámica porosa de color gris oscuro con densidades próximas a 0,3 g/cm3 en las que las paredes están formadas principalmente por una fase vítrea. La materia prima empleada se obtiene por secado de lodos procedentes de las operaciones de corte de la pizarra para techar. Los compactos en verde obtenidos en matriz flotante se sinterizaron en atmósfera de N2-5% H2 a distintas temperaturas, así como en aire a 1150ºC como material de referencia y se empleó la difracción de rayos X para determinar las fases cristalinas presentes en los materiales obtenidos. Mediante dilatometría se estudio la densificación en ambas atmósferas. La densidad alcanzada en condiciones de atmósfera no oxidante disminuye al aumentar la temperatura de sinterización, y con ello las propiedades mecánicas del material. La estructura celular empieza a desarrollarse cuando se sinteriza en N2-5% H2 por encima de 1075ºC.

Phosphorus is usually considered a contaminating element in the conventional steel industry, mainly because of its high segregation, the fragileness it gives iron and the low rate of diffusion that it has in iron. Nevertheless, phosphorus is one of the elements most often used as an alloy of sintered steels, manufactured with methods based on powder metallurgy.

Sintered high speed steels (HSSs) are assuming an increasingly important role as wear resistant and cutting tool materials, areas in which they are in competition with cemented carbides. Research o...