Additive manufacturing of Ti–6Al–4V/Al–Cu–Mg multi-material structures with a Cu interlayer

Titanium–aluminum (Ti–Al) multi-material structures have tremendous potential for use in lightweight applications. Laser powder-bed fusion (LPBF) enables the preparation of multi materials owing to its high flexibility of material modulation. However, LPBF-produced Ti–Al multi-materials are highly susceptible to interface cracking. Here, we demonstrated a novel interface welding method of unwetting titanium and aluminum alloys in LPBF by introducing a copper interlayer, which is guided by thermodynamic calculations. The Cu interlayer effectively prevented the formation of Ti–Al IMCs and suppressed interface cracking. Multi-material Ti–6Al–4 V/Al–Cu–Mg (TiA/AlA) gyroid lattices were successfully prepared via LPBF and their deformation mechanisms were revealed both experimentally and computationally. Notably, multi-material TiA/AlA lattices where TiA and AlA were directly bonded suffered from severe interface cracking caused by detrimental Ti–Al compounds. By comparison, multi-material TiA/Cu/AlA lattices were crack-free at the interface and showed a local shear fracture mode where AlA portion deforms first, followed by the TiA portion without interfacial collapse, indicating the location-specific properties.