Effect of ZrB2 particle addition on strength-ductility improvement of Al–4Fe matrix composites by laser power bed fusion

This study explores the effect of ZrB 2 particle addition on the microstructure and mechanical properties of Al–4Fe alloys fabricated by laser powder bed fusion (LPBF). High-melting-point, chemically stable ZrB 2 particles were incorporated to simultaneously improve mechanical strength and ductility of the alloys over a wide temperature range. Microstructural and phase analyses confirmed a uniform distribution of ZrB 2 particles without harmful interfacial reaction products during the LPBF process. Significant grain refinement in Al–4Fe matrix was clearly achieved from 54.5 μm to 17.9 μm by addition of ZrB 2 particles. The ZrB 2 /Al-4Fe composite exhibited improvements in both strength and ductility compared to the unreinforced Al–4Fe alloy from ambient temperature to 400 °C. Strengthening was mainly attributed to grain refinement, load transfer, and dislocation generation from the mismatch in the coefficient of thermal expansion between ZrB 2 and Al–4Fe matrix, whereas Orowan strengthening was negligible due to the micron-scale size ZrB 2 particles. Enhancement in ductility of the composite was evidenced by abundant dimple features near Zr-rich regions, indicating promoted void nucleation and coalescence that enabled localized strain accommodation. These findings demonstrate that ZrB 2 particles act both strengthening and toughening agents, highlighting the potential of ZrB 2 -reinforced Al-Fe composites for elevated-temperature structural applications.