Harnessing laser-induced in-situ nanowhiskers for high-strength aluminum alloys via additive manufacturing

The crafting of lightweight and strong aluminum alloys by additive manufacturing has long relied on expensive metal elements like Sc, Zr etc. to achieve high strength, which severely hinders their widespread applications. Here we report a costly-element-free strategy that leverages the extreme thermal gradients and laser-induced recoil pressure in laser powder bed fusion (LPBF) to in situ synthesize dense and uniformly-dispersed MgAlB₄ nano-whiskers within Al alloy matrix. Featuring diameters of 5–15 nm and aspect ratios exceeding 20, the nano-whiskers efficaciously eliminate solidification cracking and porosity, enabling near-full densification (∼99.99%) and an ultrafine equiaxed grain structure (∼1.3 μm). Marked dislocation-whisker interactions are enabled by the high aspect ratios of the nano-whiskers and their robust interfacial bonding with the Al matrix. Quasi-continuous nano-whisker networks in matrix not only promote dislocation storage and multiplication, but also allows for dislocation bypassing perpendicular to the axial direction of whiskers. The alloy thus achieves an ultimate tensile strength of ∼610 MPa and a uniform elongation of ∼8.0%. This work offers a scalable pathway toward the design and development of cost-effective, high-performance aluminum alloys by additive manufacturing.