Microstructures and mechanical properties of a newly developed high-pressure die casting Mg-Zn-RE alloy

A newly developed Mg-4Zn-2La-3Y alloy with high strength was fabricated by high-pressure die casting method, and its microstructures were thoroughly studied using transmission electron microscopy. The results demonstrate that it owns fine grains and approximately highly interconnected intermetallic phase skeletons, and exhibits ultra-high strength at both room and high temperatures. Interestingly, the eutectic intermetallic skeleton of this alloys is consisted of numerous fine particles, which are mainly consisted of two intermetallic phases, namely Wand Mg12RE. Multiple {101} twins and SFs were found in the Mg12RE phase while a few of SFs in the W phase. Additionally, minor long-period stacking ordered phase was observed in the eutectoid phase, and it probablynucleated on the Mg12RE phase following a certain OR as (0002)14H//(110)Mg12REand [11■0]14H//[1■]Mg12RE, or(0002)14H//(211)Mg12REand [11■0]14H//[1■]Mg12RE.This special intermetallic skeleton with many interfaces and planar faults can efficiently transfer dislocations across grain boundaries, and this is the key factor for the outstanding mechanical properties of the studied alloy.