Solidification behaviour and phase constituents of cast Mg-Zn-misch metal alloys

The solidification path and phase constituents of alloys in the magnesium-rich corner of the Mg-Zn-misch metal (MM) pseudo-ternary system have been investigated by a combination of differential thermal analysis, analytical electron microscopy and X-ray diffraction. The solidification behaviour diagram for this system was found to be dominated by a large two-phase (alpha-Mg plus T-phase) field in which the lowest eutectic temperature was similar to 500 degrees C. T-phase has a c-centred orthorhombic crystal structure and exhibits a wide range of stoichiometry. The interdendritic eutectic phase in the pseudo-binary Mg-MM system is Mg12MM which has the same bet structure as Mg12Ce. The eutectic temperature here is 593 degrees C.