UC Irvine

Additive Manufacturing (AM) is an emerging disruptive technology that is rapidly expanding from its initial purpose of rapid prototyping towards the production of high-quality final products. Laser powder bed fusion (LPBF) has emerged as a market leader for producing small and medium sized parts among the various classes of metal AM. While LPBF holds much promise in multiple industries, many challenges remain, particularly related to the structural evolution of AM materials during printing and the resulting material properties in the final product. A material system that has primarily defied printability is the 7xxx family of aluminum alloys. Here, we thoroughly investigate a chemically modified nanostructured Al-7068 alloy and unveil the processing-microstructure-mechanical properties relations in LPBF that underscore its performance relative to conventional (wrought) Al-7xxx alloys. Another critical challenge related to AM processing in general (and LBPF in particular) is the complex and unique thermal history experienced by each localized tiny volume in the part domain, which often results in poorly controlled heterogeneous and anisotropic microstructures, and hence properties for LBPF components. At the same time, this challenge presents an opportunity whereby one could locally control the processing parameters to induce controlled and complex temperature histories within a single part, locally tuning the microstructure and effectively resulting in the fabrication of in-situ metal-metal composites. Here we demonstrate this understanding and control in a dual-phase stainless steel (17-4 PH), quantify the differences in mechanical properties between the available microstructures, and determine the ability and scale of microstructural control. Collectively, this work paves the ground for developing superior metallic alloys for LPBF, whereby microstructure and properties are carefully controlled through the print.