Papers by Keyword: Densification Behavior

Abstract: In this investigation, the rare-earth oxide La₂O₃ combined with Al₂O₃ served as sintering additives and commercial α-SiC and B₄C powder were applied to fabricate SiC/B₄C composites by pressureless sintering. The results proved that combination of Al₂O₃ and La₂O₃ sinter additives were effective for densification of SiC/B₄C composites. The influence of sinter temperature on the phase constitution, micro-structure and densification behavior of SiC/B₄C composites was investigated.

Abstract: The SiC-B₄C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al₂O₃ combined with Er₂O₃/SiO₂ was served as sintering aids. The results were shown that the combination of Al₂O₃/Er₂O₃/SiO₂ sintering additives were effective for densification of SiC-B₄C multi-phase ceramics. The influence of B₄C content on the phase constitution, microstructure and densification behavior of the SiC-B₄C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B₄C multi-phase ceramics had similar evolvement trend when B₄C content increased. Keywords: Gas-Pressure Sintering, SiC-B₄C multi-phase ceramics, densification behavior.

Abstract: The effect of the Al₂O₃ additive on the densification behavior, microstructure and mechanical properties of the B₄C–xwt%Al₂O₃ composites sintered by means of spark plasma sintering (SPS) process were investigated. It was found that addition of Al₂O₃ improve the sinterability of B4C at temperatures between 1700 and 1800°C remarkably. The composite samples which with an addition of 4 wt% Al₂O₃ and sintering at 1750°C exhibits excellent mechanical properties (relative density: 98.82%, hardness: 90.6 HRA).

Abstract: Zirconium diboride and silicon carbide are thought to have a low intrinsic sinterability due to their strong covalent bonds, low bulk and grain boundary diffusivities. ZrB₂-SiC ceramic composites were prepared by a field assisted pressureless sintering process in the present work. The densification behavior and the effect of sintering temperature on microstructure and properties of sintered samples were studied. Pellets were in-situ formed by dry uniaxial pressing in the graphite die at a pressure of 50MPa for 3min and then sintered at a sintering temperature ranged from 1650 °C to 1950 °C with fixed heating rate and holding time. The current, voltage, temperature and displacement data were all collected by the real-time acquisition system. The bulk densities were determined by Archimedes method and the microstructure of samples was characterized by SEM. The onset of some measurable shrinkage of the green body was recorded at around 1400 °C regardless of the sintering temperature and significant shrinkage took place at higher temperature of around 1600 °C. For the sample sintered at 1950 °C, no shrinkage occurred after ~2min holding time. The relative density increased significantly with increasing temperatures and samples could be densified to a relative density of more than 99% at 1950 °C by the field assisted sintering process without obvious grain growth.

Abstract: Densification behavior of iron powder under cold stepped compaction was studied. Experimental data were also obtained for iron powder under cold stepped compaction. The elastoplastic constitutive equation based on the yield function of Shima and Oyane was implemented into a finite element program (ABAQUS) to simulate compaction responses of iron powder during cold stepped compaction. Finite element results were compared with experimental data for densification, deformed geometry and density distribution. The agreement between finite element results and experimental data was very good for iron powder. The distributions of hydrostatic pressure and the Mises stress of iron powder under cold stepped compaction were also studied.