Low frequency damping capacities and mechanical properties of Mg–Si alloys

The effect of Si content on low frequency damping capacities and mechanical properties of as-cast Mg–Si alloys were investigated. Both hypoeutectic alloys with 0.3 wt.%Si, 0.8 wt.%Si and hypereutectic alloy with 2.3 wt.%Si exhibit high damping capacities since these Mg–Si alloys possess large size α-Mg phase with very small amount of soluble atoms in it. The amount of the in situ formed Mg2Si determines the dislocation density and then influences the damping capacity of these Mg–Si alloys. The Mg–0.3 wt.%Si alloy exhibits the lowest damping value at small strain region but the highest damping value at large strain region among these Mg–Si alloys. Two damping peaks were found in Mg–Si alloys at 80 and 230 °C, respectively. But the addition of Al in Mg–Si alloy impeded the appearance of these two damping peaks since the soluble Al atoms hindered the movement of dislocations and the slide of grain boundaries. The presence of large size, brittle primary Mg2Si particles decreases the tensile strength and ductility of the hypereutectic Mg–Si alloy.