Effect of Al2Y phase on microstructure and deformation behavior of Mg-Al-Y Alloys: Insights from FIB-DIC technique

In the present work, four Mg-3Al-5Y, Mg-6Al-11Y, Mg-9Al-17Y, and Mg-11Al-21Y (wt.%) alloys, with different volume fractions of Al₂Y phase, were fabricated by mechanical stirring casting and hot extrusion. The effect of Al₂Y phase on the microstructure and deformation behavior of Mg-Al-Y alloys was investigated using the focused ion beam–digital image correlation (FIB-DIC) technique. The results show that as the volume fraction of the Al₂Y phase increases, the strength of the Mg-Al-Y alloys continuously improves, which is primarily attributed to the coefficient of thermal expansion (CTE) strengthening mechanism. The Young’s modulus also increases, owing to the high modulus of the Al₂Y phase, and the increase in modulus is more consistent with the prediction of the Reuss model. Notably, the Mg-9Al-17Y alloy achieves an optimal combination of yield strength (202.4 MPa), Young’s modulus (51.5 GPa), and ductility (7 %). The FIB-DIC technique highlights strain concentration at the Al₂Y/Mg matrix interfaces and grain boundaries, where strain compatibility is influenced by adjacent grain orientations and phase interfaces mismatch. Additionally, the size, dispersion, and distribution of Al₂Y phases play a crucial role in strain accommodation. This study provides valuable insights for the design of high-performance magnesium alloys with enhanced mechanical properties.