Hybrid additive manufacturing of Ti-Cu structures, combining powders with metallic foils

Additive manufacturing has emerged as a promising method for fabricating multi-material metallic structures. Unlike conventional additive manufacturing techniques that rely on metallic powders, the use of metallic foils offers advantages such as altered cooling rates, and modified mixing behavior, all of which can significantly influence the resulting microstructures and properties. Due to its favorable thermal and electrical properties, copper-containing multi-material systems attract both academic and industrial interest. Combined with the excellent mechanical performance of titanium alloys, the fabrication of copper–titanium multi-material components presents a unique opportunity to achieve superior thermal and mechanical characteristics. In this study, a multi-material structure was fabricated using a combination of CuCrZr powder and Ti-6Al-4V foils. Unlike the cracked powder–powder sample, the defect-free powder–foil interface shows potential for forming deformable amorphous and ultra-fine intermetallic, depending on local thermodynamic conditions. Microstructural analysis, supported by in-situ XRD measurements, showed the presence of an amorphous TiCu phase at the interface, coexisting with copper-rich intermetallics such as Cu₂Ti and Cu₃Ti₂. Computational fluid dynamics correctly simulate the observed mixing patterns and confirmed that the foil-powder combination leads to a cooling rate as high as 32500 K·s⁻¹. This rapid cooling, in combination with the local chemical compositions, promotes the formation of the amorphous TiCu phase. The characteristics and formation mechanisms of the nanoscale CuTi and CuTi₂ intermetallics compounds were thoroughly investigated. Nanoindentation-based local mechanical testing finally demonstrated that the amorphous phase is ductile, which explains why the enhanced resistance to thermal shock and interfacial cracking. This study shows in the context of multi-material printing the advantages of using powders-foils for some alloys instead of powders-powder.