Microstructural Design to Al-6Mg-5Gd alloy for the unification of structural and neutron shielding properties

Design of composition and microstructure can effective improve the structural and neutron shielding properties of neutron shielding materials. Based on the shielding standard of 30%B4C/Al, an Al-6Mg-5Gd (wt.%) alloy was designed by Shmakov-Yamamoto model and successfully fabricated by Powder Metallurgy-based routines (e.g., powder fabrication, spark plasma sintering and hot extrusion techniques). By the rapid solidification in the atomization process, the submicron cell structures were formed in powders. Due to the difference in the original powder size, the as-sintered alloys had heterogeneous microstructures, leading to the bimodal grain structures of as-extruded alloys. During these processes, the formation of nano-sized τ(C15) (Al4MgGd) phase in combination with its firstly observed transformation behavior showed the great impacts on microstructure evolutions. Therefore, the as-extruded alloy exhibited the superior yield strength (335±7MPa), ultimate tensile strength (462±5MPa) and elongation (10.2±0.3%). Through the neutron absorption test, the as-extruded alloy showed the comparable of macroscopic transmission cross section with 30%B4C/Al. In comparison with the available Al-based neutron shielding materials, our report exhibited the best unification of mechanical and functional properties. The underlying mechanisms for synergic strength-ductility behavior were discussed on the nano-sized phase strengthening, α-Al/τ interface modulation, and bimodal grain features. Critically, this work designed and studied a high-performance neutron shielding material, shedding light on the advanced structural-functional integrated materials.