UC Santa Barbara

Additive manufacturing (AM), in which complex three-dimensional (3D) shapes are created in a layer-by-layer fashion, promises a nearly limitless design space to create optimized structures for a wide range of applications, including the aerospace and medical industries. Increasingly employed to develop end products, additive manufacturing is no longer a rapid prototyping tool, and provides decreased lead time, reduced cost, customizability, and improved functionality through novel design. Although significant progress has been made in the development of advanced models that can capture the complexities of additive manufacturing processes, significant gaps in knowledge remain regarding the interplay of processing conditions and ultimate performance of additive parts, limiting their broader use in critical applications. In order to achieve improved functionality of components through novel design, a thorough understanding of microstructural development and solidification processes is required.

This work focuses on the application of a novel 3D characterization technique, specifically TriBeam tomography, to characterize additively manufactured metals in their as-deposited state. Serial sectioning experiments performed within a scanning electron microscope (SEM) provide comprehensive, multi-modal datasets. Structural, chemical, and crystallographic information were collected to probe AM structures at the scale of the melt pool, on the order of a cubic millimeter. Progress in the automation of the 3D characterization process, including improvements to the collection, segmentation, and reconstruction of 3D data will be presented. Rather than focus on a single material or manufacturing process, the utility of 3D characterization is demonstrated across AM metals in general, with a focus on some of the most common alloys currently available. Using 3D data and advanced thermal modelling codes, a previously developed microstructure prediction model is calibrated for an AM process, and applied for bulk microstructure prediction over a range of processing parameters and grain morphologies. Additional information only accessible via 3D characterization will provide insight into the evolution of microstructure and role of defects during part fabrication. Finally, a pathway to develop alloys that are specifically designed for the unique rigors of AM processes will be presented.