Effects of Precipitates and Alloying Element on Microstructure and High Temperature Properties of Mg-Al Alloys
The effects of precipitates and alloying element on the high temperature tensile properties of Mg-Al alloys were investigated in this study. In order to modify the precipitation behavior and microstructure of Mg-Al alloys, Sr and/or Mm (Misch metal) were added to the Mg-9Al and AZ91 alloys. All test specimens used in this study were die-cast on a 320 ton cold chamber high-pressure die-casting machine and the microstructures of the specimens were examined by optical and scanning electron microscopy. Tensile tests were carried out at room temperature, 150oC and 200oC at a strain rate of 2×10-4/sec. The microstructure analyses revealed that thermally stable MgAlSr and AlMm compounds were precipitated in the Sr and/or Mm added alloys and these compounds suppressed the precipitation of the discontinuous Mg17Al12 phase at grain boundaries. The high temperature mechanical properties of the Mg-Al alloys were found to increase with the addition of Sr and/or Mm. It was concluded that the addition of Sr and/or Mm improved high temperature tensile properties of the Mg-Al alloys by the formation of thermally stable precipitates.
Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie
Y. J. Chung and K. S. Shin, "Effects of Precipitates and Alloying Element on Microstructure and High Temperature Properties of Mg-Al Alloys", Materials Science Forum, Vols. 475-479, pp. 537-540, 2005