Michael Christopher Maguire

Comparative Shock Response of Additively Manufactured Versus Conventionally Wrought 304L Stainless Steel.

Gas-gun experiments have probed the compression and release behavior of impact-loaded 304L stainless steel specimens that were machined from additively manufactured (AM) blocks as well as baseline ingot-derived bar stock. The AM technology permits direct fabrication of net- or near-net-shape metal parts. For the present investigation, velocity interferometer (VISAR) diagnostics provided time-resolved measurements of sample response for one-dimensional (i.e., uniaxial strain) shock compression to peak stresses ranging from 0.2 to 7.0 GPa. The acquired wave-profile data have been analyzed to determine the comparative Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high-pressure yield strength of the AM and conventional materials. The possible contributions of various factors, such as composition, porosity, microstructure (e.g., grain size and morphology), residual stress, and/or sample axis orientation relative to the additive manufacturing deposition trajectory, are considered...

Comparing Field Emission Electron Microprobe to Traditional EPMA for Analysis of Metallurgical Specimens

The use of a thermal field emission electron source and other design changes have significantly increased the resolution of electron probe microanalysis (EPMA), especially in the 5-8kV range of accelerating voltage.[1,2] The analysis of particles/phases as small as 200 nm in diameter has been documented for geological and meteoritical specimens and a similar analytical volume was shown in a Sn-Ag solder alloy.[1,2] The following work highlights other examples of field emission EPMA for the analysis of fine-scale metallurgical microstructures. Features too small for traditional EPMA, such as fine-scale lamellar transformations and microsegregation in solidification microstructures, can now be analyzed successfully with FE-EPMA. The high resolution is obtained while simultaneously covering a long linescan length or a relatively large area for mapping.