MICROSTRUCTURE AND CASTABILITY OF Mg-Al-La ALLOYS FOR HIGH CONDUCTIVITY APPLICATIONS

Magnesium die-casting alloys based on the Mg-Al (magnesium-aluminum) system have been used increasingly in many industrial applications for the main purpose of weight savings. However, relatively low conductivity of conventional Mg-Al casting alloys such as AZ91 often limits the application areas and attempts to improve the conductivity without losing excellent casting capabilities and other properties of the Mg-Al based alloys that have been made recently. In this research. aluminum content was restricted to a comparatively low level for improving the conductivity and lanthanum (La) was added to compensate for reduced casting capabilities. As the La content was increased, the mold filling ability measured using a fluidity serpentine test mold was gradually increased, however the hot cracking susceptibility was observed to he initially increased and then decreased. The relationship between solidification characteristics and castabilities of Mg-3Al-xLa alloys was determined based on the thermal and cooling curve analysis results and micro structural characterization.