In Situ Reactive Printing of Aluminum Matrix Composite with Ultra-High Volume Fraction Reinforcement.

Additive manufacturing (AM) can fabricate intricate structures that are infeasible or uneconomical for conventional manufacturing methods. Its unique capabilities have motivated emergence of several printing technologies and extensive research in material adoption in particular ferrous-, Ti-, and Ni-based alloys. Meanwhile, the large freezing range and high reflectivity of aluminum, a lightweight structural material, greatly reduce aluminum's compatibility with AM. The incompatibility roots from aluminum's unstable behavior in the rapid cyclic thermal conditions in AM and its poor interaction with laser. This hinders the development of laser-based aluminum AM and deteriorates the existing lack of lightweight structural materials in the intermediate temperature range. Aluminum matrix composites (AMCs) have great potential to serve as thermally stable lightweight structural materials, combining lightweight nature of aluminum matrix and strength of reinforcement phases. However, fabrication of AMC largely uses conventional methods, achieving only moderate volume fraction of reinforcement while having limited part complexity compared with AM. To address these challenges, in situ reactive printing (IRP) is adopted as a novel AM method, harnessing the reaction product of dissimilar elemental powder mix to fabricate AMC with an ultra-high volume fraction of intermetallic reinforcement. In this study, the effect of titanium addition to elemental aluminum feedstock powder is systematically studied on different aspects, including material processability, microstructural features, and mechanical performances. The results show that IRP can overcome the incompatibility between AM and aluminum and produce AMC with exceptional volume fraction of reinforcements and outstanding stiffness enhancement when compared with existing AM aluminum alloys and other AMCs.