4D printing of recoverable buckling-induced architected iron-based shape memory alloys

Architected materials exhibit extraordinary properties in comparison with conventional materials and structures, resulting in additional functionality and efficiency by engineering the geometry in harmony with the base ma-terial. Buckling-induced architected materials (BIAMs) are a class of architected materials that exhibit a sig-nificant potential to absorb and dissipate energy owing to their local instabilities. Previous studies have shown a trade-off between energy dissipation and geometrical recoverability in metallic BIAM, which limits their use in applications that require both of these features. This study, for the first time, presents 4D printing of buckling -induced architected iron-based shape memory alloys (BIA Fe-SMAs) using laser powder bed fusion (LPBF). The results show that 4D printing of BIA Fe-SMAs can offer both energy dissipation and geometrical recoverability (i. e., recentring). The study was conducted on two different alloy compositions of Fe-17Mn-5Si-10Cr-4Ni. Quasi -static cyclic tests were performed on the two BIA Fe-SMAs, and the samples were subsequently heated to 200 symbolscript to activate the shape memory effect (SME) of the base material. The samples could recover the residual de-formations accumulated during the cyclic load owing to the SME of the base material, which led to shape -recovery ratios of 96.8 and 98.7% for the studied BIA Fe-SMAs. The results of this study demonstrate that 4D printing of BIA Fe-SMAs can yield an enhanced multi-functional behavior by combining the material's inherent functional behavior with the functionalities of the architected structure. Notably, BIA Fe-SMA samples could reconfigure their initial shape without damage after densification, which sets them apart from conventional crushable lattices.