The growth of the UAl4 phase in an UAl3/Al diffusion couple was treated as a planar moving boundary problem due to diffusion of Al and U atoms in the direction perpendicular to the interface surface. The diffusion problem was carried out by using a simulation package which combined data evaluated by Thermo-Calc with a mobility database. A thermodynamic database of the U–Al system, suitable for the Thermo-Calc code, was composed using data from literature. The mobility database was assessed from reported experimental growth of the UAl4 phase at different temperatures. The Al tracer diffusion coefficient in the UAl4 phase was described by:

D(m2/s) = 2.7 x 10-1exp[-209.5(kJ/mol)/RT]

under the assumption that uranium mobility was negligible.

Simulation of UAl4 Growth in an UAl3/Al Diffusion Couple. L.Kniznik, P.R.Alonso, P.H.Gargano, G.H.Rubiolo: Journal of Nuclear Materials, 2011, 414[2], 309-15