X-ray computed micro tomography as complementary method for the characterization of activated porous ceramic preforms

Abstract

X-ray computed micro tomography (CT) is an alternative technique to the classical methods such as mercury intrusion (MIP) and gas pycnometry (HP) to obtain the porosity, pore-size distribution, and density of porous materials. Besides the advantage of being a nondestructive method, it gives not only bulk properties, but also spatially resolved information. In the present work, uniaxially pressed porous alumina performs activated by titanium were analyzed with both the classical techniques and CT. The benefits and disadvantages of the applied measurement techniques were pointed out and discussed. With the generated data, development was proposed for an infiltration model under ideal conditions for the production of metal matrix composites (MMC) by pressureless melt infiltration of porous ceramic preforms. Therefore, the reliability of the results, received from different investigation techniques, was proved statistically and stereologically.

Experimental Models for Activtation Mechanism of Pressureless Infiltration in the Non‐Wetting Steel‐Alumina MMC System

“…The average next nearest Ti interparticle distance in the activator containing layer is between 53 and 70 lm. [18] As soon as such melt bridges are established, the steel melt can propagate along the existing melt surfaces.…”

“…[18] It was observed that the infiltration behaviour improves with increasing Ti particle number, but not with increasing the concentration using larger Ti particles. In order to simulate variable density and size of the activator particles three liltographic masks were prepared.…”

“…[16,17] Preliminary experiments on preforms have shown that activator concentration and size are important parameters for infiltration. [18] Therefore, model pores with different dot sizes and densities were prepared. The diameter of the dots and distances among them were tuned lithographically.…”

Activation Mechanism and Infiltration Kinetic for Pressureless Melt Infiltration of Ti Activated Al2O3 Preforms by High Melting Alloy

“…The average distance between activator particles is thus the most critical parameter. The maximum surface to surface distance between nearest neighbor particles for which under the given conditions infiltration was observed, is between 20 and 30 mm [35] The latter value is the average next nearest neighbor distance for A100T40 samples with 3 wt% Ti, which did not infiltrate at all. This threshold range is consistent with the observation that none of the A100T200 samples were infiltrated, in which the nearest neighbor distance is above the threshold value ($25 mm) even for the sample with the highest activator content (20 wt%; 42 mm).…”

“…[35]. The set of experiments was made with a X3CrNiMo13-4 steel (Bö hler AG; Switzerland, Walisellen).…”