Simulation of UAl_4 growth in an UAl_3/Al diffusion couple

摘要

In this work the growth of the UAl_4 phase in an UAl _3/Al diffusion couple is 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 the DICTRA simulation package which combines 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 UAl_4 phase at different temperatures. The Al tracer diffusion coefficient in the UAl _4 phase, DAl(UAl_4)(m~2/s)=2.7×10 ~(-1)exp(-209500(J/mol)/RT), is obtained under the assumption that uranium mobility is negligible.