Ti2AlC and Ti3SiC2 MAX phase foams: processing, porosity characterization and connection between processing parameters and porosity

Proceeding of: World PM2016 Congress Proceedings. New materials and applications, biomedical applicationsMAX phases Ti2AlC and Ti3SiC2 foams with controlled porosity and pore size were produced using the space holder method. The foams were processed using water-leachable crystalline carbohydrate as space holder that involves: mixing, cold isostatic pressing, dissolution and sintering. Three combinations of volume percentage (20%-60%) and size distribution (250-1000 mum) of space holder were introduced during mixing. The foams were characterized and compared with the material without space holder. The characterization included: morphology (overall, open and closed porosity by Archimedes method) and gas permeability. Foams with porosity up to about 60 vol% and pore size distribution ranging from about 250 to 1000 mum were produced. Experimental porosity was compared to the theoretical expected porosity. The results show a bimodal porosity that can be customized by the sintering and the space holder. This study connects the processing parameters to the porosity created and allows control of porosity and pore size to produce tailor-made properties.The authors would like to thank the funding provided for this research by the Regional Government of Madrid- Dir. Gral. Universidades e Investigación, through the project S2013/MIT-2862 (MULTIMAT-CHALLENGE-CM), and by Spanish Government through Ramón y Cajal contract RYC-2014-15014 and the project MAT2012/38650-C02-0

Interfacial design of Cu-based composites prepared by powder metallurgy for heat sink applications

Thermal aspects are becoming increasingly important for the reliability of the electronic components due to the continuous progress of the electronic industries. Therefore, the effective thermal management is a key issue for packaging of high performance semiconductors. The ideal material working as heat sink and heat spreader should have a CTE of (4-8) × 10-6 K-1 and a high thermal conductivity. Metal matrix composites offer the possibility to tailor the properties of a metal by adding an appropriate reinforcement phase and to meet the demands in thermal management.http://www.sciencedirect.com/science/article/B6TXD-4NK4G71-1/1/50620dd9a257eaca4c01d63891e3380

Cu-based composites prepared by powder metallurgy for thermal management of electronic devices

Thermal aspects are becoming increasingly important for the reliability of the electronic components due to the continuous progress of the electronic industries such as the higher output power and the higher level of integration of ICs. To achieve long life and reliable performance of these components, it is necessary to keep the operating temperature of the electronic device within specified limits. Therefore, the effective thermal management is a key issue for packaging of high performance semiconductors. The ideal thermal management material working as heat sink and heat spreader should have a CTE (coefficient of thermal expansion) of 4 ppm/K to 8 ppm/K and a high thermal conductivity. The aim of this work is the development of copper matrix composites reinforced with diamond or SiC in order to obtain a composite material having a thermal conductivity higher than 400 W/mK in case of copper/diamond or higher than 300 W/mK in case of Cu/SiC. The Cu-based composites reinforced with diamond or SiC particles were fabricated by a powder metallurgical method (powder mixing with subsequent pressure assisted consolidation). In order to design the interfacial behaviour between copper and the reinforcement different alloying elements were added to the copper matrix or coated powders were used in case of SiC. The thermophysical properties will be displayed and discussed as a function of the reinforcements as well as the alloying element used for composite preparation. The differences between coated and uncoated powders will be discussed

TFP reinforced metal - one way to increase the specific strength

The integration of fibers, especially tailor fiber placement (TFP), in metal matrices offers one way to generate composite materials with increased specific strength compared to the unreinforced metal matrix. The TFP can be adapted according to the final load paths through the component and can be covered partially or fully with the metal. Following this approach load transfer elements can be built, transferring much load and having low mass. First fields of application are identified in building and automotive industry. This work includes the powder metallurgical manufacturing process using Spark Plasma Sintering (SPS) technique, the characterization of the microstructure and the tensile test of different specimens (sintered copper, TFP (as received) and TFP (Cu covered) reinforced copper). Experimental result on 19.5 vol.% TFP (Cu covered) reinforced copper shows an increase of specific strength around a factor of 2.2 compared to pure copper

High-entropy alloy CoCrFeMnNi produced by powder metallurgy

Lately high-entropy alloys (HEAs) have been the topic of extensive research, as these materials are promising candidates for many challenging applications, as for example tools, moulds and functional coatings. In contrast to conventional alloys, HEAs consist of five or more principal elements, each having a concentration between 5 and 35 at.-%. Against expectations, HEAs show a rather simple microstructure consisting preferentially of cubic phases. Due to this microstructure, HEAs show promising properties, e.g. in terms of high-temperature stability, high strength and ductility. Within this research, a single-phase CoCrFeMnNi HEA was produced by powder metallurgy (PM). In contrast to conventional metallurgy, PM offers a lot of advantages, e.g. good material efficiency and high shape complexity. Gas atomised powder was used and selected PM methods are presented (e.g. pressureless sintering, spark plasma sintering, additive manufacturing (EBM)). The process methods were evaluated by characterising the material properties (density, microstructure, mechanical properties) of the compacted and sintered samples

Silver/diamond composite material - powder metallurgical route and thermo-physical properties

To meet the need of high-performance thermal management materials in the field of electronic applications, heat sink materials reinforced with synthetic diamonds have been prepared via powder metallurgy. A matrix of a silver alloy with a silicon content of 0.45 wt.% was chosen out of the prediction of the thickness of a final carbide layer of about 180 nm. The volume content of the diamonds and the diamond size were kept constant. The mixed powders were consolidated by Spark Plasma Sintering (SPS) using different sintering temperatures between 800 and 870 °C with a holding time of 30 min. The maximum thermal conductivity of 680 W/(mK) measured at room temperature and 620 W/(mK) at 275 °C was obtained at 810 °C sintering temperature. The degradation of the most promising sample after one thermal cycle up to 275 °C was determined below 1 percent of the value after sintering

Spark plasma sintering and hot extrusion of aluminium alloy powder

The Spark Plasma Sintering (SPS) is a promising sintering technology to produce dense bulk pre-compacts from micro- or nano-structured aluminium alloys at lower temperatures and shorter sintering times. The densification behaviour and sintering response of an atomized Al-Si alloy sintered by SPS was investigated. A high density of bulk material with porosity less than 1 % can be prepared by SPS with a temperature of 450 deg C, holding for 2-5min and a pressure of 170 MPa. The particle size of the prealloyed powder influencing its electrical resistance plays a crucial role at the finding of the optimum processing parameters in case of a power-controlled sintering regime. In addition, the homogeneity of the microstructure across the diameter of the sintered samples are investigated and correlated with in-situ measurements of the temperature distribution within the samples. Residual porosity is mainly localised at the margin close to the wall of the die, corresponding to the lowest measured temperatures. The influence of the process parameters on the structure and tensile properties of subsequently hot extruded material was studied. The mechanical tensile properties of the SPSed compacts are significantly lower compared to that of the extruded material due to some residual porosity and the weakness of the joint between the initial atomized alloy powder particles. The extruded P/M material offers superior mechanical strength to the comparable compositions of known die cast piston alloys

Materials for biomass combustion atmospheres

High temperature corrosion is one major challenge for biomass gasification materials. FeCrAl alloys have proven to have superior resistance to oxidation in air and combustion atmospheres. However, for an industrial application, these alloys must be joined to a conventional high-temperature alloy to cut down material costs. In this study the resistance of FeCrAl alloys with different aluminum contents in synthetic gasifier atmosphere is presented. Simultaneously, their properties after being soldered to Nicrofer 3220H (1.4876) and thermally cycled with high heating and cooling rates in air are revealed