Additive manufacturing is a promising process that has the capability to build components with complex geometries for structural and biomedical applications. Due to the rapid and localized directional solidification of molten metallic alloys, unique phase transformations occur at the melt pool that can provide for components with greater strength and other improved mechanical properties. However, knowledge gaps remain at how additive manufacturing processing influences the resulting properties. Knowledge gaps include the mechanisms behind powder flow behavior entering the melt pool, how powder flow influences characteristics of the melt pool, how porosity forms during the process, and the anisotropy of microstructures, porosity and mechanical properties in an additive manufactured part. This work utilized both in-situ and ex-situ methods to characterize the powder-blown additive manufacturing process, or directed energy deposition (DED), of 316L stainless steel (SS), Ti-6Al-4V, and Inconel 718. In-situ high-speed X-ray imaging allowed real-time observation of the liquid-solid interface of a fluctuating melt pool and porosity formation during the process. In-situ infrared imaging also enabled the capture of temperature variation during the process. Ex-situ methods included characterization of the resulting parts with optical microscopy, X-ray diffraction, Vickers microhardness indentation, and tensile testing, etc. Collaboration with computational efforts allowed for calibration, validation of thermal models that enable prediction of properties of an additive manufactured part.

Creator

• Wolff, Sarah

DOI

• https://doi.org/10.21985/n2-vfnr-8542

Subject

• Materials Science
• Mechanical engineering

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:14448
• etdadmin_upload_626097

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright