Influence of cross correlations on interdiffusion in Al-rich Al-Ni melts

Abstract

The relation of self-and interdiffusion in a liquid metal, particularly the influence of cross correlations at low concentrations, is studied experimentally. Accurate interdiffusion data are obtained by a combination of x-ray radiography with the shear-cell method on the ground and on the sounding rocket MAPHEUS under microgravity conditions. Self-diffusion coefficients, measured by quasielastic neutron scattering, increase with decreasing Ni concentration, whereas interdiffusion coefficients are about constant. We show that cross correlations influence interdiffusion even at concentrations as low as 2 at. % Ni. Consequently, Darken's equation is not valid in this case.

Overview of In Situ X-Ray Studies of Light Alloy Solidification in Microgravity

“…Using a linear shear-cell technique even materials that sediment on melting or that show largely different melting and liquidus temperatures can be handled [29,30]. The shear-cell was successfully operated aboard the DLR sounding rocket MAPHEUS-4 in the MIDAS-M setup investigating the influence on cross correlations on interdiffusion in Al-rich Al-Ni alloys [31]. By implementing a newly developed ultra-high temperature shear-cell chemical diffusion in binary Al-Ti and Si-Ge alloys will be investigated aboard MAXUS-9 in spring 2017 using the XRMON-DIFF MAXUS-9 setup.…”

XRISE-M: X-radiography facility for solidification and diffusion studies of alloys aboard sounding rockets

“…By the still sharp difference in contrast at the separation line it can be concluded that no major shear-convection occurred. This is due to the slower shear-speed chosen with respect to an earlier measurement on Al-Ni alloys aboard MAPHEUS-4 16 . In Fig.…”

“…In order to demonstrate the capability of this facility compared with previous reports from ground experiments 15,23 and a sounding rocket experiment 16 the right capillary which showed a bubble only towards the This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.…”

“…X-radiography has proven a versatile tool in monitoring metallurgical processes in-situ and in real time. Using X-radiography metal foaming 1,2 , alloy solidification [3][4][5][6][7][8][9][10][11][12][13][14] , and chemical diffusion in binary liquid alloys [15][16][17] have been studied both on ground and in microgravity. In particular, microgravity research requires compact and lightweight facilities that make optimal use of the short periods of processing time available aboard parabolic flights or sounding rockets, or the even more expensive processing time on long-duration platforms such as reentry satellites or the International Space Station (ISS).…”

“…For microgravity times of minutes, sounding rockets are the microgravity platforms of choice. Experiments have been recently reported making again use of a sounding rocket X-radiography facility developed by DLR 16 and of a facility developed by Swedish Space Corporation 14,20 . Common to both facilities is that a single experiment could be performed in flight and calibration of the imaging system has to a) Corresponding author:florian.kargl@dlr.de be carried out well ahead of the actual flight in case of SSC's MASER sounding rocket module or as part of a late access activity for the DLR sounding-rocket module used aboard MAPHEUS-4.…”