The grain boundary internal friction of pure Al and the same Al doped with different amounts of Ga (10, 50 and 410ppm) was measured before and after high temperature deformation in 2 different modes (static tensile creep, cyclic reverse torsion). It was found that, without deformation, smaller amounts of Ga (10 and 50ppm) slightly increased but larger amounts of Ga (410ppm) clearly increased the activation energy. Following tensile creep, the peak height for Al-10ppmGa and Al-50ppmGa decreased to a lower level but remained, at a higher level after cyclic torsion, than that for pure Al and Al-410ppmGa. The results were explained in terms of perturbations in the grain boundaries due to slip and grain boundary roughening for stationary boundaries and an enhanced sliding by grain boundary migration. Migration and roughening were promoted by Ga contents up to 50ppm while the effects were diminished by higher amounts of Ga. This was consistent with previous observations that smaller amounts of Ga increased the grain boundary mobility in pure Al.

The Effect of Ga on Internal Friction of Pure Al Before and After Deformation. Y.Shi, B.Cai, Q.P.Kong, P.Cui, G.Gottstein: Journal of Materials Science, 2003, 38[9], 1895-9