Fabrication of bimetallic interpenetrating structures with enhanced impact resistance via 3D-printing of high-entropy alloy lattices and vacuum melt infiltration of Al-based alloys

Lattice truss architectures fabricated from CoCrFeMnNi high-entropy alloys (HEAs) through the precision of Laser Powder Bed Fusion (L-PBF) technology were subsequently enhanced via vacuum impregnation with an aluminium alloy, resulting in the creation of a sophisticated bimetallic interpenetrating phase composite (IPC) architecture. Upon exposure to high-speed impact loading using a Split-Hopkinson Pressure Bar (SHPB), these IPCs exhibited exceptional comprehensive impact resistance, particularly notable for their superior energy absorption capabilities. This enhanced performance is attributed to the seamless integration of the distinctive physical properties of the HEA and the Al-based alloy, which together enable coordinated deformation of the bimetallic phases during impact. Detailed analysis of the metallurgical bonding microstructure at the bimetallic interfaces revealed the formation of robust bonding structures both during the impregnation process and after impact-induced failure, with the strengthening effect at the dissimilar material interfaces playing a crucial role in energy absorption by amplifying energy dissipation through crack propagation in the diffusion interface layer. Notably, under equivalent mass conditions, the impact resistance of these IPCs significantly surpasses that of the Al-based alloy alone, demonstrating the potential of this engineered, hierarchical structure as a lightweight, impact-resistant material.