Abstract
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.