Browsing by Keyword "Sintering"
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Item The initial stage of liquid phase sintering for an Al-14Si-2.5Cu-0.5Mg (wt%) P/M alloy(2010-06) Arribas, I.; Martín, J. M.; Castro, F.; TRAZABILIDAD CIRCULARThe present paper focuses on the initial stage of the liquid phase sintering (LPS) of a commercially available P/M Al-Si alloy, with nominal composition Al-14Si-2.5Cu-0.5Mg (in wt%). The microstructural examination of the as-received powder showed that it is constituted by pure Al particles and master alloy particles with composition Al-28Si-5Cu-1Mg (in wt%). Its compressibility is lower than for the conventional elemental P/M aluminium premixes, but it is still better than for prealloyed Al powders and other P/M powders. Thermogravimetry experiments showed that the elimination of the organic lubricant takes place between 275 and 490°C during heating to the sintering temperature. The phase transformations leading to the formation of the liquid phase were studied by differential scanning calorimetry (DSC). The dimensional changes associated with the generation of the liquid were measured by dilatometry. Samples quenched into water from different temperatures (between 450 and 575°C) and times (between 0 and 30min) were studied to reveal the microstructural evolution of the alloy. The first liquid is formed inside the master alloy particles at around 505°C. This liquid spreads across the compact, enhancing the chemical homogenization of the material. The alloying elements diffuse from the liquid inside the originally pure Al particles, reducing their melting temperature. This alloying process is almost concluded at around 535°C. When the temperature is increased the liquid starts to be formed also in the originally pure Al particles. The melting of the FCC Al-rich phase finishes around 575-590°C. The full melting of the alloy occurs at about 635-645°C. After analyzing the different possible causes, it is concluded that the main swelling mechanism is the volume change associated with the melting of a fraction of the material when the temperature is increased. The phases detected by X-ray diffraction (XRD) in the as-received powder and in the sintered compact are FCC Al-rich solid solution, Si, θ-phase (CuAl2), and Q-phase (Cu2Mg8Si6Al5).Item A Step towards A Robust Binder Jetting Technology: Process Parameter Optimization for 17-4PH Steel to Increase Powder Bed Homogeneity(European Powder Metallurgy Association (EPMA), 2020) Lores, A.; Azurmendi, N.; Agote, I.; Andrés, U.; EXTREMATThe inhomogeneity in properties of parts manufactured by Binder Jetting is one of the main concerns for the industrial adoption of the technology. It has been observed that parts manufactured in the same print-job present some deviations in density and dimensional accuracy. Therefore, the aim of this work is to develop a robust process parameter configuration for a commercial grade 17-4 PH stainless steel alloy. Sample parts were distributed along the build envelope to map the powder bed inhomogeneities. Then, through statistical analysis, the effect that different process parameters have over powder bed properties variations (green density, sintered density and dimensions) was studied. In summary, the present study throws some insight about the parameter effect in process homogeneity, allowing the optimization thereof and the reduction of properties variation, giving the opportunity to made great strides towards the industrial adoption of the technology.Item Ti3SiC2-Cf composites by spark plasma sintering:: Processing, microstructure and thermo-mechanical properties(2019-08) Lagos, M.A.; Pellegrini, C.; Agote, I.; Azurmendi, N.; Barcena, J.; Parco, M.; Silvestroni, L.; Zoli, L.; Sciti, D.; EXTREMATMAX phases, and particularly Ti3SiC2, are interesting for high temperature applications. The addition of carbon fibers can be used to reduce the density and to modify the properties of the matrix. This work presents the densification and characterization of Ti3SiC2 based composites with short carbon fibers using a fast and simple fabrication approach: dry mixing and densification by Spark Plasma Sintering. Good densification level was obtained below 1400 °C even with a high amount of fibers. The reaction of the fibers with the matrix is limited thanks to the fast processing time and depends on the amount of fibers in the composite. Bending strength at room temperature, between 437 and 120 MPa, is in the range of conventional CMCs with short fibers and according to the resistance of the matrix and the presence of residual porosity. Thermo-mechanical properties of the composites up to 1500 °C are also presented.