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Interdiffuion in Ternary Aluminium-Base Alloys Under High Pressure

Tomoshi Takahashi 

Department of Materials Science and Engineering, Niihama National College of Technology, Niihama, Japan

Abstract


Pressure, as well as temperature and component, is one of important
factors which determine the existing states in materials. In
particular, the properties of materials are changed the extreme states
of high-pressures and high temperatures, and the substances and
structures, which are not capable of obtaining under ordinary
pressure, appear under the high-pressure. In the case of manufacturing
new materials, diffusion phenomena of constituting atoms are utilized
under high pressure as well as the ordinary pressure, but it is
thought that the diffusion under high-pressure occurs under
considerably different situations comparing with the atmospheric
pressure. Diffusion is a basic and important factor for understanding
and discussing the phenomena such as the recrystallization,
homogenization, aging, precipitation, etc. Therefore, it is necessary
to obtain the information for diffusion in Al-base ternary alloys
under high-pressures. In the present work, the interdiffusion
coefficients in the $B&A(J-fcc phase of the Al-Cu-Zn,
Al-Cu-Mg and Al-Zn-Mg alloys have been determined under pressures from
0.101 to 3000 MPa in the temperature ranges from 793 to 868 K. The
direct interdiffusion coefficients Dii(i=Cu, Zn, Mg) are positive, and
the indirect interdiffusion coefficients Dij(i$B!b(Jj) are
negative in the Al-Cu-Zn and Al-Zn-Mg systems. The interdiffusion
coefficients decrease with increasing pressure. The activation
energies for the interdiffusion and impurity diffusion increase with
pressure. The ratios of the activation volume to the molar volume of
each aluminum alloy ,$B-y(JV/V0, are 0.96-1.05 (Al-Cu-Zn
system), 1.01-1.08 (Al-Cu-Mg system) and 0.99-1.10 (Al-Zn-Mg system).
Their values for the ternary aluminum alloys are slightly larger than
those of the binary Al-Cu, Al-Zn and Al-Mg alloys.

 

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Presentation: oral at High Pressure School 1999 (3rd), by Tomoshi Takahashi
See On-line Journal of High Pressure School 1999 (3rd)

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