Innovative 4D printing strategies for developping architected microstructures

Developing architected microstructures in Laser Powder Bed Fusion (LPBF) requires modifying microstructures during the printing process. A recent approach leverages the laser in LPBF as a heat source for in-situ Selective Laser Heat Treatments (SLHT). Due to the high cooling rates (10³ to 10⁸) in LPBF of Ti-6Al-4V (Ti64), a martensitic microstructure typically forms in the as-built state. Optimizing SLHT parameters from Finite Element (FEM) simulations, it is possible to reach cooling rates between 3 000 and 8 000 °C/s In subsequent heat treatments, while maintaining a sub-transus temperature. This enables the decomposition of the α' martensite, creating a composite microstructure with alternating layers of α' and (α+β) phases. These innovative 4D printing strategies can be generalized to other types of alloys.