Hot Tearing Behavior in Double Ternary Eutectic Alloy System: Mg-Ce-Al Alloys

The hot tearing behaviors of double ternary eutectic alloy system, Mg-4Ce-xAl (x = 0 to 9 wt pct) alloys, were evaluated by a CRC mold. The occurrences of hot tearing were determined by the Volumetric contraction force–Temperature–Time curves combining the solidification paths simulated by Thermo-Calc software. The ratio of drop-in force to final force reflected the severity of hot tearing from the point of micro perspective, its tendency was consistent with the hot tearing susceptibility. Affected by the double ternary eutectic reactions and solidification phases evolution, unlike general alloys, the hot tearing susceptibility curve of Mg-4Ce-xAl alloys contained two peak points. Compared with the hot tearing susceptibility of binary Mg-Al and Mg-Ce alloys, the peak points in Mg-4Ce-xAl alloys were later than that in Mg-Al and Mg-Ce alloys due to the faster diffusion accelerated by the solidification phase of Al11Ce3. The nucleation, propagation and healing of hot tear cracks were affected by the types, fractions, sizes and distributions of solidification phases which mainly included Mg12Ce, Al11Ce3 and Mg17Al12 in addition to the matrix Mg.