Additive manufacturing promises a major transformation of the production of high economic value metallic materials, enabling innovative, geometrically complex designs with minimal material waste. The overarching challenge is to design alloys that are compatible with the unique additive processing conditions while maintaining material properties sufficient for the challenging environments encountered in energy, space, and nuclear applications. Here we describe a class of high strength, defect-resistant 3D printable superalloys containing approximately equal parts of Co and Ni along with Al, Cr, Ta and W that possess strengths in excess of 1.1 GPa in as-printed and post-processed forms and tensile ductilities of greater than 13% at room temperature. These alloys are amenable to crack-free 3D printing via electron beam melting (EBM) with preheat as well as selective laser melting (SLM) with limited preheat. Alloy design principles are described along with the structure and properties of EBM and SLM CoNi-base materials.

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Exposure to high heat can cause polymer matrix composites (PMC) to fail under mechanical loads easily sustained at room temperature. However, heat is removed and temperature reduced in PMCs by active cooling through an internal vascular network. Here we compare structural survival of PMCs under thermomechanical loading with and without active cooling. Microchannels are incorporated into autoclave-cured carbon fiber/epoxy composites using sacrificial fibers. Time-tofailure, material temperature, and heat removal rates are measured during simultaneous heating on one face (5-75 kW/m 2 ) and compressive loading (100-250 MPa). The effects of applied compressive load, heat flux, channel spacing, coolant flow rate, and channel distance from the heated surface are examined. Actively cooled composites containing 0.33% channel volume fraction survive without structural failure for longer than 30 minutes under 200 MPa compressive loading and 60 kW/m 2 heat flux. In dramatic comparison, non-cooled composites fail in less than a minute under the same loading conditions.

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