Effect of precipitation on internal friction of AZ91 magnesium alloy
(Department of Materials for Special Environments, Institute of Metal Research,
Chinese Academy of Sciences, Shenyang 110016, China)
Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: The effect of precipitation on the internal friction (IF) of AZ91 magnesium alloy was investigated by using X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) observation, and dynamic mechanical analysis (DMA). Six different states of alloy were prepared by applying different heat treatment processes: as-cast, in-complete solid solution, complete solid solution, micro-precipitation, continuous precipitation and continuous−discontinuous precipitation. It was found that the internal friction of in-completely solid-solutionized, completely solid-solutionized and micro-precipitated specimens showed a similar characteristic, and the grain boundary relaxation is completed depressed due to the Al atoms supersaturated in the α-Mg solution. However, a thermal relaxation internal friction peak was observed for continuously precipitated and continuously− discontinuously precipitated specimens at around 438 K and frequency of about 1 Hz, which was attributed to the grain boundaries relaxation. Furthermore, it was found that the relaxation of the β-Mg17Al12/α-Mg phase interfaces should give its contribution to the background internal friction in the as-cast, continuously precipitated and continuously−discontinuously precipitated specimens.
Key words: precipitation; solutionization; isothermal treatment; aging; internal friction