Formation of Amorphous and Non-Equilibrium Phases in Ti-Cu and Ti-Ni Alloys Synthesized by Mechanical Alloying Under a High Pressure

A. Dobromyslov 

Russian Academy of Sciences, Ural Division, Institute of Metal Physics, 18 S.Kovalevskaya str., GSP-170, Ekaterinburg 620219, Russian Federation

Abstract


Non-equilibrium and amorphous states can be obtained in different
alloys synthesized from elemental powders by mechanical alloying under
a high pressure. The Ti-Cu and Ti-Ni alloys were prepared by
mechanical alloying elemental powders of nickel or copper and titanium
at room temperature using a pressure technique. For this mixture of
powders of different composition was pressed at up to 5 GPa between
Bridgmen anvils and deformed by rotation of one anvil about the other.
The structure of prepared alloys was investigated by X-ray diffraction
and transmission electron microscopy. We have studied the
microstructures and the phase states of Ti-Cu and Ti-Ni binary alloys
synthesized from powders by mechanical alloying. This study has
revealed that the investigated alloys have nanodispersed and amorphous
structure. The microstructure of Ti sample subjected to severe plastic
deformation is sufficiently homogeneous with large-angle
misorientations of fragments. Intense texture maxima were observed on
(1101) diffraction line of the a-phase. Our results show that severe
plastic deformation at room temperature under quasistatic pressure
leads to nanostructures. The grain size in pure titanium is 10-20 nm.
The grain size decreases with the increase of Cu or Ni in the alloy to
1 nm. The equilibrium solid solubilities of both Cu or Ni in Ti and Ti
in Cu or Ni are small at room temperature. Mechanical alloying under
high pressure increases the solid solubility of alloying elements
essentially. The solubility of Cu into Ti is 10 at.%. The solubility
of Ni into Ti is 7 at.%. It was found that the alloys containing from
80 to 100 at.% Cu or Ni consisted only of the FCC solid solution. The
solubilities of Ti into Cu or of Ti into Ni are 20 at.%. Amorphous
phase forms in alloys containing from 11 to 80 at.% Cu or from 13 to
80 at. % Ni. We noticed that the equiatomic composition is more
suitable for obtaining of this phase state. The amorphous phase in
Ti-Cu and Ti-Ni systems is observed in the composition region, where
intermetallic compounds exist in the equilibrium phase diagram. Effect
of various heat treatments on the fine structure of synthesized alloys
has been studied. The process of mechanical alloying elemental powders
is described as a peritectoid reaction.

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Presentation: poster at High Pressure School 1999 (3rd), by A. Dobromyslov
See On-line Journal of High Pressure School 1999 (3rd)

Submitted: 2003-02-16 17:33
Revised:   2009-06-08 12:55
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