Grain boundary relaxation behavior in meso-grained dilute magnesium alloys

Abstract

The impact of alloying element on the anelastic behavior at temperatures from 273 to 573 K was examined using pure magnesium and eight solid-solution binary magnesium alloys. All alloys, as well as pure magnesium, had meso-grained structures with an average grain size of approximately 30 µm. Measurement of the damping capacity revealed the occurrence of grain boundary relaxation at intermediate and elevated temperatures in all materials. The onset temperature for grain boundary relaxation depended on the alloying element. Pure magnesium and four binary alloys (Mg–Al, Mg–Li, Mg–Mn and Mg–Sn alloys) had an activation energy of approximately 1 eV, which is close to that of grain boundary diffusion in magnesium; in contrast, higher activation energies were obtained for some alloys, i.e., ~ 1.5 eV for the Mg–Ag and Mg–Zn alloys, and ~ 2–3 eV for the Mg–Ca and Mg–Y alloys, respectively. This work reveals that grain boundary segregation of the solute atoms is an influential factor for grain boundary relaxation in magnesium alloys.