Papers by Keyword: Field Activated

Abstract: TiB₂-TiC+Ni/TiAl/Ti graded materials were prepared by field-activated pressure-assisted synthesis process (FAPAS) and the mechanical properties and residual stress were investigated. Shear fracture that occurs at the interface between the cermets and TiAl with the maximum shear strength of 85.88 MPa. The residual stress and deformation induced by the thermal effect of chemical reaction and Joule heat during the synthesis process were analyzed by nonlinear finite element simulation. It is demonstrated that the maximum equivalent residual stress locate in the transition layer between the ceramics and TiAl, consistent with the shear test result.

Abstract: Iron disilicide (-FeSi2, and -FeSi2+Cu0.1wt%) were prepared by a field-activated pressure assisted synthesis(FAPAS) method from elemental powders and the thermoelectric properties were investigated. The average grain size of these products is about 0.3m. The thermal conductivity of these materials is 3-4wm-1K-1in the temperature range 300-725K. These products’ figure of merit is 28.50×10-4 in the temperature range 330-450K. The additions of Cu promote the phase transformation of -Fe2Si5 + -FeSi → β-FeSi2 and shorten the annealing time. It is proved that FAPAS is a benign and rapid process for sintering of -FeSi2 thermoelectric materials.

Abstract: In this paper, the synthesis of four-layered functionally graded materials (FGMs) samples of (TiC)pNi/TiAl with titanium substrate by field-activated and pressure-assisted synthesis process (FAPAS) was investigated. It was shown that the TiC particles formed by in-situ combustion synthesis process were fine and distributed uniformly. Moreover, the imposition of the electric field and the combustion reaction of TiAl is the key for the successful synthesis of the FGMs during the process. The microstructure, phase composition of the interfaces and mechanical properties of the graded material were characterized. Moreover, the sample has an excellent thermal shock resistance ability and gradient distribution of micro-hardness across the substrate layers and the surface layer.

Abstract: Iron disilicide（-FeSi2）compounds were synthesized by field-activated pressure assisted synthesis (FAPAS) process, and their thermoelectric properties were measured. Fine microstructure with small pores was obtained in the fabricated samples. The average grain size was approximately 0.3 m. The thermal conductivity in the temperature range of 300-725 K was 3-4 Wm-1K-1, which was considerably lower than that of the same materials synthesized by other methods including SPS process. Lower thermal conductivity provided a higher figure of merit, ZT of 28.50×10-4 in the temperature range of 330-450 K.

Abstract: In this paper, the synthesis of four-layered functionally graded materials (FGMs) samples of (TiB2)pNi/(TiB2)p(Ni+Ni3Al)/ Ni3Al with different metallic substrate (Ni, Cu and Cr-Ni steel) by field-activated and pressure-assisted synthesis process (FAPAS) was investigated. It was shown that the imposition of the electric field and the combustion reaction of Ni3Al is the key for the successful synthesis of the FGMs during process. The exothermal reaction of the powder of nickel and aluminum during combustion enhanced the diffusion bonding in the interfaces subsequently. The microstructure, phase composition of the interfaces and mechanical properties of the graded materials were characterized, which showed indicative formation of firm bonds by the combustion reactive process. The samples have an excellent thermal shock resistance ability and gradient distribution of micro-hardness across the substrate layers and the surface layer.

Abstract: Using the processes of field-activated and pressure-assisted combustion synthesis (FAPACS), FGM materials (FGMs) were prepared under the conditions of field-assisted and the hot-press. The microstructure and the phase composition of the interface of the graded materials were investigated and the results showed that the metallurgical joining layer was formed in the interfaces of the (TiB2)pNi/Ni3Al/405 steel. The mechanical characterization of the gradient materials showed that the composition and the micro-hardness of the gradient material were gradient distributed, and its surface Rockwell hardness and wear resistance are better than that of hardened 20Cr steel.