Low Frequency Relaxation Effect Observed in Al-Mg Alloy

Abstract

Al-12 wt% Mg alloys have been studied by isothermal mechanical spectroscopy. The samples were quenched then annealed at various temperatures. Experiments were performed in a very large frequency range (10-4Hz – 50 Hz) between room and solidus temperatures. For each temperature of measurement, experiment started after complete microstructure stabilization of the sample and therefore the transient effects due for instance to β (( and β′ precipitation were not observed. Nevertheless, a new relaxation effect was obtained in the reversion temperature range. This effect is not thermally activated. It is maximal at about 0.1 Hz and increases with the temperature of measurement. It completely disappears after annealing at solid solution temperature and successive slow cooling and therefore is linked to the β precipitates. This effect is interpreted as a phase transformation at the precipitate surface induced by the applied stress.

Mechanical spectroscopy study of as-cast and additive manufactured AlSi10Mg

“…On the basis of relaxation parameters this can not be excluded, however it is noteworthy that Zener peaks have been observed in Al-Mg alloys with a quite larger Mg content than that of our alloy [28]. For example, Benyahia et al [39] investigated the Al-12 wt% Mg alloy and the peak was observed only after solution treatment and quench when a lot of Mg atoms are in supersaturated solid solution. On these grounds we do not believe that the origin of peak P2 can be ascribed to a Zener mechanism.…”

“…A relaxation peak with similar characteristics (H = 1.1 eV, τ0 = 4.0 x 10 -14 s) was reported by Atodiresei et al [38] for the Al-4 at% Mg alloy and was discussed in terms of a solute-dislocation interaction model. Benyahia et al [39] attributed to a Zener relaxation mechanism a peak with H = 1.09 eV, τ0 = 2.0 x 10 -14 s observed in the Al-12 wt% Mg alloy. Golovin et al [40][41][42][43][44] investigated anelastic processes occurring in Al-Mg alloys in an extended range of Mg concentrations (up to 12 wt%) and under different heat treatment conditions.…”