Rev.Adv.Mater.Sci. (RAMS)
No 3, Vol. 18, 2008, pages 264-268

STRUCTURE OF NANOCRYSTALLINE Ti-BASE ALLOYS OBTAINED BY MECHANICAL
ALLOYING AND ULTRA HIGH PRESSURE SINTERING

Jan Dutkiewicz, Wojciech Maziarz and Lucyna Jaworska

Abstract

The Ti-base alloys with additions of Ta and Nb had been ball milled and subsequently sintered using ultra high pressure Bridgeman method. The milled powders with structure of α-Ti solid solution and average crystallite size of 10 nm and particle size of 5 µm were hot pressed under 4 GPa for 1 min at temperature 650 úC. This technique allowed preserving the structure of the examined alloys at a nanometric level. The grain size of alloys after UHP sintering changed from 25 up to 90 nm with an increase of content of the elements stabilizing the β phase in the alloy. The nucleation and growth of the β phase during sintering were major factors, which controlled the final structure of the sintered alloy. The Ti alloys containing additions of either Ta or Nb consisted mainly of the α-Ti structure with different fractions of β-Ti phase, whereas additions of both Ta and Nb generally increased the fraction of the β-Ti phase. Conventional TEM diffraction studies confirmed the presence of α-Ti and β-Ti phases in the investigated powders and HREM was applied to measure the grain size of both α and β phases.

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