SOLIDIFICATION BEHAVIOR AND PHASE CONSTITUENTS OF CAST MG-ZN-MISCH METAL-ALLOYS

The solidification path and phase constituents of alloys in the magnes ium-rich corner of the Mg-Zn-misch metal (MM) pseudo-ternary system ha ve been investigated by a combination of differential thermal analysis , analytical electron microscopy and X-ray diffraction. The solidifica tion 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 eute ctic temperature was similar to 500 degrees C. T-phase has a c-centred orthorhombic crystal structure and exhibits a wide range of stoichiom etry. The interdendritic eutectic phase in the pseudo-binary Mg-MM sys tem is Mg12MM which has the same bet structure as Mg12Ce. The eutectic temperature here is 593 degrees C.