STRUCTURE AND PROPERTIES OF RAPIDLY SOLIDIFIED MG-AL-ZN-ND ALLOYS

The microstructural characteristics and decomposition behavior of rapi d solidified Mg-6wt.%Al-3wt.%Zn-3wt.%Nd and Mg-6wt.%Al-3wt.%Zn-6wt.%Nd alloys have been investigated by a combination of optical microscopy, transmission electron microscopy and energy dispersive spectroscopy. The microstructure of rapidly solidified ribbon consisted of 0.3-0.5 m u m size alpha-Mg cells, 10 nm scale Al2Nd particles and 0.05-0.1 mu m size Al11Nd3 related phase. Fine Al2Nd particles wee distributed homo geneously in the wheel side of the ribbon, while clusters of Al2Nd par ticles were present locally at the alpha-Mg cell boundaries in the air side of the ribbon. With increasing Nd content, the volume fraction o f the Al2Nd phase increased and the distribution of the Al2Nd phase be came homogeneous even in the air side of the ribbon. An orientation re lationship between Al2Nd and Al11Nd3 related phase was observed in the present study. The rapidly solidified Mg-Al-Zn-Nd alloy showed improv ed mechanical properties due to the presence of the fine Al2Nd phase p articles. especially at elevated temperatures up to 350 degrees C. (C) 1997 Elsevier Science S.A.