  A high-throughput experimental approach is presented to extract the
anisotropic interdiffusion coefficient by combining information over the
composition profiles obtained by the electron probe microanalysis (EPMA) and
the grain orientation spectrum by the electron backscatter diffraction (EBSD)
on polycrystalline diffusion couples. Following the forward-simulation scheme,
the interdiffusion coefficients in grains with diverse orientation are obtained
and subsequently used to determine the anisotropic interdiffusion coefficients
perpendicular (D_\perp (x)) and parallel (D_\parallel (x)) to the c axis of the
hcp Mg lattice in a Mg-Al alloy as a function of the Al solute content at 673 K
and 723 K, respectively. It was found that the interdiffusion coefficients
generally increased with the Al content and the rotation angle with respect to
the c axis with a valley point around {\theta} approx 30 {\deg} at 723 K. And
it was noticed that diffusion along the basal plane was always faster than
along the c axis. A comprehensive explicit expression of the interdiffusion
coefficients was provided as a function of Al content, grain orientation and
temperature. The anisotropic impurity diffusion coefficients of Al in hcp Mg
derived by the extrapolation of the results in this paper are in good agreement
with first principles calculations in the literature.
