Dual role of Al2Y phase for heterogeneous microstructure and strength–plasticity synergy in Mg-Y-Al alloys via continuous squeeze casting-extrusion

Abstract

In this paper, the effects of the content and morphology of Al 2 Y phase on the microstructures and mechanical properties of Mg-1.5nY-nAl ( n = 0.5, 1.0, 1.5, 2.0) alloys fabricated by continuous squeeze casting-extrusion(CSCE) process are investigated. The increase in the content of Y and Al elements leads to the formation of primary Al 2 Y particles in the alloys. The exposed {222} close-packed plane of Al 2 Y exhibits a similar crystal structure to that of α-Mg, thereby acting as a nucleation site for α-Mg and significantly refining the as-cast microstructure. During CSCE process, the primary Al 2 Y particles not only trigger particle-stimulated nucleation (PSN) but also exhibit a well-defined orientation relationship with the surrounding recrystallized α-Mg grains, specifically {222} Al2Y //{0001} Mg and < 211 > Al2Y // < 11–20 > Mg . Furthermore, the content and distribution of eutectic Al 2 Y phase markedly affect the dynamic recrystallization (DRX) behavior. The dendritic eutectic Al 2 Y phase is crushed during hot extrusion, hinders the passage of dislocations, and plays a PSN-like role in promoting DRX. Notably, a higher eutectic Al 2 Y content leads to an increased DRX fraction. The alloy designed with the composition of Mg-2.25Y-1.5Al (wt.%) has the best comprehensive mechanical properties, achieving an ultimate tensile strength of 314.3 MPa, a yield strength of 257.6 MPa, and an elongation of 11.6%. This superior performance is attributed to a heterogeneous microstructure consisting of both recrystallized and deformed grains, with heterogeneous structure strengthening identified as the key enabler of the synergy between strength and ductility.

The authors' abstract, as published at the source. Journal of Magnesium and Alloys, 2026 · DOI ↗