7 research outputs found
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Sintering maps for ceramic-filled-glass composites
Ceramic-filled-glass (CFG) composites densify by viscous flow during final-stage, non-reactive, liquid-phase sintering (NLPS). The rate of densification is controlled by the viscosity of the CFG composite dispersion during sintering, which is determined by the concentration of ceramic filler in the composite, and the viscosity of the suspending glass medium. A mathematical expression has been developed that determines the critical filler concentration in a given viscosity glass at which high-density CFG composites will be produced in a given time during final-stage NLPS. This expression has been used to predict the effects of sintering time, pore size, and glass viscosity on critical filler concentration, and to construct final-stage sintering maps that provide guidelines for designing and processing high-density CFG composites. 12 refs., 2 figs
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Ceramic granule strength variability and compaction behavior
Diametral compression strength distributions and the compaction behavior and of irregular shape 150--200 {mu}m ceramic granules and uniform-size 210 {mu}m glass spheres were measured to determine how granule strength variability relates to compaction behavior of granular assemblies. High variability in strength, represented by low Weibull modulus values (m<3) was observed for ceramic granules having a distribution of sizes and shapes, and for uniform-size glass spheres. Compaction pressure data were also analyzed using a Weibull distribution function, and the results were very similar to those obtained from the diametral compression strength tests for the same material. This similarity suggests that it may be possible to model granule compaction using a weakest link theory, whereby an assemblage of granules is viewed as the links of a chain, and failure of the weakest granule (i.e., the weakest link) leads to rearrangement and compaction. Additionally, with the use of Weibull statistics, it appears to be possible to infer the variability in strength of individual granules from a simple pressure compaction test, circumventing the tedious task of testing individual granules
Refinement of master densification curves for sintering of titanium
An approximate master curve for the densification of cold-pressed titanium powder during vacuum sintering was published previously. It was based on the combined results for three different titanium powders. The master densification curve model incorporates the effects of particle size, compaction pressure, sintering time, and sintering temperature on densification. The collection of a large amount of additional data now allows refinement of the model. Distinct curves are presented for three different titanium powders, prealloyed Ti6Al4V, and Ti-Ni binary alloys. The master densification curve is sigmoidal, but deviates from the ideal form at high sintered density; the relative sintered density saturates at 90 to 100 pct, depending on the particle size of the titanium powder, and to a lesser extent the compaction pressure. The master densification curve below the saturation level is slightly dependent on the compaction pressure. © 2010 The Minerals, Metals & Materials Society and ASM International