Additive manufacturing of metal matrix composites via nanofunctionalization
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esearch Letter
Additive manufacturing of metal matrix composites via nanofunctionalization John H. Martin, Brennan D. Yahata, Eric C. Clough, Justin A. Mayer, Jacob M. Hundley, and Tobias A. Schaedler, HRL Laboratories LLC, Malibu, California 90265-4797, USA Address all correspondence to John H. Martin at [email protected] (Received 9 March 2018; accepted 3 May 2018)
Abstract A novel, alloy-agnostic, nanofunctionalization process has been utilized to produce metal matrix composites (MMCs) via additive manufacturing, providing new geometric freedom for MMC design. MMCs were produced with the addition of tungsten carbide nanoparticles to commercially available AlSi10Mg alloy powder. Tungsten carbide was chosen due to the potential for coherent crystallographic phases that were identified utilizing a lattice-matching approach to promote wetting and increase dislocation interactions. Structures were produced with evenly distributed strengthening phases leading to tensile strengths >385 MPa and a 50% decrease in wear rate over the commercially available AlSi10Mg alloy at only 1 vol% loading of tungsten carbide.
Metal matrix composites (MMCs) offer a unique set of material properties enabling their use in many specialized, highperformance applications, including brake disks and turbine blades.[1] Introducing a secondary hard phase into an otherwise ductile metal matrix can produce a composite system with improved modulus, strength, and creep life, as well as reduced wear rates.[2–4] These benefits are generally only seen in specific applications due to the difficulty in processing these materials into more complex shapes.[2,5] Additive manufacturing (AM), commonly referred to as three-dimensional (3D) printing, provides a processing route to complex geometries. However, there has been scant prior work on methods of producing MMCs utilizing AM.[6] Here we present a nanofunctionalization approach for additive feedstock that enables alloy and machine agnostic 3D printing of new aluminum MMCs with >20% increase in strength and >2 × improvement in wear characteristics over the baseline alloy system. Methods currently used for MMC manufacturing include stir casting and powder consolidation.[7,8] The former is limited due to the reactivity of the reinforcement phase and tendency for settling during casting, while the latter is limited to simple geometries (e.g., flat sheets, prismatic sections).[9,10] Both are additionally susceptible to agglomeration of the reinforcement phase and generally require some form of post-processing or machining to produce a final usable geometry. This is often an expensive process due to increased tool wear from the reinforcement phase. There is no industrially relevant production route to geometrically complex MMCs. This ultimately limits the use of these alloy systems despite clear material property advantages over typical metal alloys.
AM provides a method for net shape production of components with limited post-processing and is theoretically applicable to almost any alloy system.[11] Recent work by
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