Concentration Dependence of Internal Friction in Al-Mg Alloy

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Abstract
An internal friction peak in a series of Al‐Mg alloys containing up to 12.1 wt% Mg has been studied at torsional frequencies in the range 0.4 to 98 Hz. The temperature at which the maximum occurred was found to vary according to the Arrhenius equation with an activation energy of 1.4 eV. The peak height was found to be proportional to C C where CAl and CMg are the atomic concentrations of Al and Mg, respectively. The peak as measured after slow furnace cooling, at 0.4 Hz, was displaced to lower temperatures as a result of quenching. The magnitude of this displacement appeared to increase with increasing Mg concentration. – The results, coupled with those of complementary electron microscopy and X‐ray lattice parameter studies, substantiate previous interpretation of the peak in 5 to 7% Mg alloys at ≈ 1 Hz as being due to Zener reordering.