Diffusion in the titanium-nickel system: II. calculations of chemical and intrinsic diffusion coefficients |
| |
Authors: | G F Bastin G D Rieck |
| |
Affiliation: | (1) University of Technology, Eindhoven, Netherlands |
| |
Abstract: | Diffusion coefficients in the Ti-Ni system have been calculated by the aid of equations given by Sauer and Freise, and Wagner.
Values for the TiNi (50 at. pct Ni) phase were found to be:D
u
(cm2/s) = 0.0020 exp - 142,000/R for the temperature range between 650 and 940°C. The heat of activation, expressed in J/mol,
has an accuracy of ±6000. For the β-Ti(Ni) phase containing 6 at. pct Ni the temperature dependence of the diffusion coefficient
is expressed by:D
u
(cm2/s) = 0.0688 exp - 141,000/RT. The uncertainty in the energy of activation is ±12000 J/mol. No clear variation of the diffusion
coefficient with concentration could be detected. It was found that Ni is by far the fastest moving component in β-Ti(Ni),
Ti2Ni and TiNi (at least in the composition range between 50 and 53 at. pct Ni). Values ofD
Ni/D
Ti have been calculated with an equation derived by van Loo. The significance of the calculated values is critically examined.
By means of a practical example it is shown that the calculated ratio of the intrinsic diffusion coefficients can be extremely
sensitive to slight variations in the position of the marker interface.Diffusion coefficients in the Ti-Ni system have been
calculated by the aid of equations given by Sauer and Freise, and Wagner. Values for the TiNi (50 at. pct Ni) phase were found
to be:D
u (cm2/s) = 0.0020 exp - 142,000/R for the temperature range between 650 and 940°C. The heat of activation, expressed in J/mol,
has an accuracy of ±6000. For the β-Ti(Ni) phase containing 6 at. pct Ni the temperature dependence of the diffusion coefficient
is expressed by:D
u (cm2/s) = 0.0688 exp - 141,000/RT. The uncertainty in the energy of activation is ±12000 J/mol. No clear variation of the diffusion
coefficient with concentration could be detected. It was found that Ni is by far the fastest moving component in β-Ti(Ni),
Ti2Ni and TiNi (at least in the composition range between 50 and 53 at. pct Ni). Values ofD
Ni/D
Ti have been calculated with an equation derived by van Loo. The significance of the calculated values is critically examined.
By means of a practical example it is shown that the calculated ratio of the intrinsic diffusion coefficients can be extremely
sensitive to slight variations in the position of the marker interface.
This paper is based on a Thesis submitted by G. F. BASTIN in fulfillment of requirements for the degree of Doctor in Technological
Sciences. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|