Design
Materials
Process
Diffusion Measurements in Liquid Nickel
J.P. Leonard1, T.J. Renk2, M.J. Aziz1 December 2002
(1)Division of Engineering and Applied Science, Harvard University, Cambridge MA (2)Sandia National Laboratories, Albuquerque NM
Currently, little information exists for diffusion of impurities in molten refractory metals. This is owing to not only the high temperatures needed to melt, but also to the high reactivity, convective processes, and surface contamination that is nearly always present in bulk liquid metals. However, pulsed ion-beam melting has been shown to be a useful and accurate technique to measure diffusion constants as it is free from the above complications and sources of error.
Figure 1. Concentration profiles Mo-implanted nickel. Open circles are as-implanted concentration profile, solid circles are diffused profile after melting. Solid line is the best-fit profile from numerical calculations.
Figure 2. Concentration profiles W-implanted nickel. Open circles are as-implanted concentration profile, solid circles are diffused profile after melting. Solid line is the best-fit profile from numerical calculations.
The current set of experiments look at diffusion of the impurities Al, Cr, Cu, Fe, Mn in Nickel. By implanting each into pure nickel, then melting with a pulsed ion beam, it is possible to infer diffusion constants via comparison of SIMS profile information before and after the melt. In addition, knowledge of temperature evolution is needed, obtained via existing rapid melting and solidification simulations, which provides the input to a diffusion simulation to iteratively explore which diffusion values provide the best fit to the resulting impurity profile.
Publications relating to this project
- J.P. Leonard, M.J. Aziz, T.J. Renk, M.O. Thompson, “Solute diffusion in liquid nickel measured by pulsed ion beam melting”, Metal. Mater. Trans. A, 35, 2803, (2004).