Quasicrystalline powders

Key words quasicrystalline powders, consolidation, high quasihydrostatic pressure... 

Quasicrystalline powders behave while consolidation in many features like ceramic materials and are consolidated with difficulties. Usually it is performed by HIP technique, but this process takes rather much time and requires complicated equipment. In our former works [1] it was shown that the consolidation of ceramic powders is significantly easier when using high quasihydrostatic pressure that activates particle contact interaction, and high-temperature sintering requires 2-3 min. 

From the utmost points in the curve in Fig. 1 we obtained an average evaluative value of the yield stress of the porous billet from quasicrystalline powder cs=0.6 GPa in the process of preliminary pressing. Just this stress is optimum for forming billets. The shape of the curve is an evidence of the powder with quasicrystalline component to conduct while preliminary... 

The deviations from the average value for the utmost points of the curve do not exceed 0.1 GPa (6 %). This result is an evidence of the fact that a porous body from the quasicrystalline powder deforms under a high quasihydrostatic pressure as porous bodies from plastic material. Thus, it is shown that the effective pressure P for the consolidation of a powder billet of Al63Cu25Fei2 in the high-pressure apparatus is... 

Amorphous powder formed by mechanical alloying for 510 h at intensity 5 was further milled at intensity 7 for 25 h. The typical broad diffuse maximum of the amorphous state disappeared, and the characteristic intensity distribution of the quasicrystalline phase showed up in the X-ray diffraction pattern. Therefore, additional milling at higher intensity led to an amorphous-to-quasicrystal transition. Amorphization can also be achieved for crystalline starting powder mechanically alloyed for 206 h at intensity 9 by a further milling for 433 h at intensity 3 [3.108]. 

CONSOLIDATION OF AL-CU-FE POWDERS WITH QUASICRYSTALLINE COMPONENT BY USING HIGH QUASIHYDROSTATIC PRESSURES... 

Consolidation ofAl-Cu-Fe powders with a quasicrystalline component... 

Thus, there are found the technological conditions for consolidating powders with quasicrystalline component that allow to sinter dense quasicrystalline samples with the porosity 0 < 2 %. Compacted samples in the form of cylinders of 6 mm in diameter and of about 5 mm in height were manufactured. 

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