Sintering of icosahedral quasicrystalline Al-Cu-Fe powders using high quasihydrostatic pressure

Mykola O. Yefimov ,  Yuly V. Milman ,  Dina V. Lotsko ,  Sergey V. Ulshin ,  Izabella I. Timofeeva ,  Miroslav V. Karpets ,  Olexander I. Bykov 

Institute for Problems of Materials Science, 3, Krzhizhanovsky, Kyiv 03142, Ukraine

Abstract

The processes accompanying the sintering of quasicrystalline Al-Cu-Fe powders were investigated. Pure Al-Cu-Fe powders and powders alloyed by 0.3 wt.% Sc and 11 wt.% Cr were chosen for studies. Quasicrystalline powders were produced by water atomization technique. The technology of sintering with high quasihydrostatic pressure was used. High-temperature sintering under high quasihydrostatic pressure was realized in the high-pressure cell of “lentil” type. Sintering was carried out at 700 С during 2 min using the pressure range from 2.8 up to 7 GPa. The optimum pressure of preliminary cold pressing (0.6 GPа) and high temperature pressing (3-4 GPа) were determined. The compacts with porosity < 2% were obtained. The phase compositions of compacts were studied by X-ray diffractometry and SEM techniques. Microhardness was measured by Vickers indenter at a load of 2 N. Using the original technique developed by authors the plasticity characteristic δH of the sintered quasicrystalline compacts was determined from the microhardness values as well.
The annealed Al-Cu-Fe and Al-Cu-Fe-Sc compacts were obtained in the single-phase quasicrystalline state whereas the Al-Cu-Fe-Cr compacts - in the single-phase approximant state.
It is revealed that microhardness of sintered compacts noticeably lowers with the growth of the sintering pressure, whereas line broadening in X-ray patterns of compacts increases. The analysis of line broadening in X-ray patterns has shown a progressive growth of the density of phason defects in quasicrystalline lattice with increasing the sintering pressure.
The stress-strain curves were obtained for all sintered compacts. The stages of strengthening and softening are observed for all deformation curves. However, the softening stage on deformation curve of Al-Cu-Fe-Cr compacts (approximant phase) is shorter than for the samples of the quasicrystalline phase. In all sintered compacts the δH=0.67-0.70.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium I, by Mykola O. Yefimov
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-04 14:53
Revised:   2009-06-07 00:44
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