Effect of Mischmetal on Microstructure and Mechanical Properties of Superlight Mg-Li Alloys.

The influence of mischmetal (lanthanum and cerium) on the microstructure and mechanical properties of Mg-9Li-3Al- x RE ( x =0, 0.5, 1, 1.5, 2, wt%) alloys was investigated by optical microscope, scanning electron microscope (SEM) with an energy dispersive spectroscope (EDS), and X-ray diffraction (XRD). In as-cast alloys, Al 4 RE phase is formed, the content of Mg 17 Al 12 phase and the volume fraction of α- Mg phase decrease. In addition, α -Mg phase is refined and the mechanical properties of Mg-9Li-3Al- x RE alloys are improved. However, with increasing mischmetal content, the size of Al 4 RE phase increases and the mechanical properties decrease. In extruded alloys, Al 4 RE phase is broken into the particles of 1∼3 μm in the β -Li matrix phase and α/β interphase. And the best mechanical properties are obtained for Mg-9Li-3Al-1.5RE alloy with a tensile strength of 228.3MPa and elongation of 20.8%, increased by 88.6% and 197.4%, respectively, compared with as-cast Mg-9Li-3Al alloy. [ABSTRACT FROM AUTHOR]