Shubo Gao

Abstract

Engineering heterostructured alloys through novel directed energy deposition processes

Additive manufacturing (AM) has transformed metal fabrication, not only by enabling complex geometries but also by offering unprecedented control over microstructure through localized melting and solidification. Among AM processes, directed energy deposition (DED) is particularly attractive for fabricating large metallic components. However, conventional DED often produces coarse columnar grains under steep thermal gradients, limiting microstructural control. In this talk, I will discuss how innovations in laser beam shaping and multi-material delivery open new pathways to architect heterostructures across length scales. I will first show that coaxial annular-beam laser-wire DED enables the formation of bimodal grain structures through localized wire retention and recrystallization of incompletely melted wire, offering a new route to tailoring grain heterogeneity. Taking beam shaping further, adjustable core–ring laser beams are being explored to tailor solidification conditions and promote equiaxed grain formation in crack-sensitive refractory alloys. Beyond single alloys, multi-material DED enables spatial control of chemical heterogeneity within a single build, where the interplay between feedstock chemistry and melt-pool dilution govern phase formation, interfacial integrity, and mechanical response. These studies demonstrate how AM process innovations can serve as a key lever for designing high-performance heterostructured alloys.