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Microwave-cast material dating from the latest prototype development period and subsequent TRL 7 advancement testing was sent to LANL for additional characterization. The initial characterization described here is considered a supplement to and verification of that performed by Y-12 during the Technology Readiness Assessment process. The carbon chemistry results from Y-12 and LANL regarding early prototype microwave cast test object (CTO) and cylinder castings match within expectations. Only one fully intact as-cast CTO was available for examination in which carbon chemistry does not appear to vary spatially, at least at relatively low carbon levels (hypoeutectic). The large as-cast grain size leads to relatively poor grain size statistics and similar difficulties were encountered during the TRA. Small, isolated gas pores were observed in four of the five metallographic samples in prototype CTO casting PT-01. Finally, the next phase of characterization work, which focuses on corrosion behavior, has started and is described briefly. ∑ Foundry and Solidification Science Team Los Alamos National Laboratory 2.1) Metallographic Preparation The Sigma-2 Characterization Team received the five location-specific numbered samples for metallographic preparation, inclusion analysis, and grain size determination. Sample preparation consisted of mounting, grinding, and polishing the samples. Inclusion analysis consisted of Energy Dispersive Spectroscopy (EDS) and image analysis for inclusion size and distribution. Samples were mounted in the as-received condition. A cold mounting procedure using Epon 815C epoxy with Diethylenetriamine (10:1 ratio) followed by overnight curing under pressure (~1000 psi). All samples were initially ground through a series of decreasingly abrasive steps (Table 1) in order to ensure that the sample is planar and that any damaged layers from initial sample preparation are removed. Table 1: Notes on initial grinding steps for metallographic preparation. Grinding Paper Lubricant Platen Speed Time 120 grit Water High Until planar 320 grit Water High ~ 1.5 minutes 600 grit Water High ~ 2 minutes 800 grit Water Low ~ 2 minutes

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