Effect of Mg and Zn additions on the phase structure, welding behavior and mechanical properties of Al–5Gd thermal-neutron absorbing alloys

To overcome the embrittlement and limited structural reliability of B 4 C/Al-based composites, Mg- and Zn-containing Al–5Gd thermal-neutron absorbing alloys were fabricated. Mg and Zn additions promoted the formation of Al 2 Gd 0.45 Mg 0.55 and Al 6.3 Gd 3 Zn 4.7 phases, respectively. The annealed Al-5Gd–5Mg alloy achieved a tensile strength of 305 MPa with 15.4% elongation, while Al-5Gd–5Zn exhibited 22.2% elongation at 149 MPa. After TIG welding, all alloys fractured in the heat-affected zone and showed reduced strength and ductility. Monte Carlo simulations confirm that both ternary alloys provide higher thermal-neutron absorption efficiency compared to 30 wt% B 4 C/Al composite. These results demonstrate that Al-Gd-Mg/Zn alloys provide a promising alloying route for lightweight neutron-shielding structural materials with improved mechanical property and weld-joint reliability.