Internal friction peaks associated with the precipitation in AZ91 magnesium alloy

In the present study, the low-frequency internal friction behavior of AZ91 magnesium alloy was investigated with the objective of giving more information on the precipitation process. Two internal friction peaks were found at around 165 and 314 °C during heating process for aged AZ91 alloy, in which the low-temperature peak is attributed to viscous sliding of the α-Mg grain boundaries, but the viscous sliding of the β-Mg17Al12/α-Mg phase interfaces may also give its contribution to the appearance of the peak. The high-temperature peak is resulted from the phase transformation associated with the dissolution of the precipitates at high temperature.