OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Infrastructure & Advanced Manufacturing; Advanced Materials OBJECTIVE: Use computational tools to develop new refractory alloy compositions for use in additive manufacturing of high temperature hypersonic flight components. DESCRIPTION: This topic seeks the development of novel refractory metal alloy compositions that enhance reliability and additive manufacturability of components for hypersonic flight vehicles. Extreme environmental conditions require structural components of hypersonic flight vehicles such as pintles, nosecones, and control surfaces to exhibit high specific strength and temperature resiliency. This has led to renewed interest in refractory metal alloys (e.g., tungsten, molybdenum), as they can withstand these temperatures and loads. Moreover, additive manufacturing (AM) is of particular focus for such alloys due to the advantages of enabled complex geometries, fewer tooling costs, and reduced scrap rate. Challenges to broad adoption of refractory alloy AM within the Missile Defense System are twofold. First, most existing alloys were developed for wrought and powder metallurgical processes. AM build variables such as thermal cycling, gradients, and alloy properties are known to induce solidification cracking, excess grain growth, and transition across the ductile-to-brittle transition mid-build. Second, many refractory ore or refinery locations are such that defense supply chains may become contested in the event of regional conflicts. As such, alternative refractory alloy compositions that help allay these manufacturing and supply chain hurdles are needed, with application to both test targets and interceptors. Integrated computational materials engineering (ICME) tools have demonstrated the ability to conduct rapid evaluation and optimization of candidate materials based on desired properties, resulting in appreciable cost and time savings compared to traditional guess and check methodologies of development. Performance criteria for evaluating refractory alloy candidates include, but are not limited to, thermophysical properties such as thermal expansion, thermal conductivity, and specific heat; specific strength; and additive manufacturing quality metrics such as build density vs. bulk value and build defect prevention. The developed alloys should show the ability to perform in environments representative of hypersonic flight. Consideration of geographic locations for both ore extraction and primary metal production facilities of constituent alloy elements is also important, specifically large production in either the United States or North America. Lastly, the developed alloys must be cost effective with a well-developed technology transition plan for powder or wire feedstock production sufficient for meeting the emerging needs of the hypersonic industrial base. PHASE I: Demonstrate the feasibility of the proposed alloy development approach via program implementation and algorithm testing. The algorithms must consider cost, material performance, and supply chain resiliency, with rationale provided regarding their respective weights. Performers should identify firms or in-house capabilities for maturing production of novel AM powders and obtain rough order of magnitude pricing for initial powder batches or wire feedstock. Provide test plans for determining AM parameters and material properties, and obtain rough order of magnitude pricing for initial batch powder or wire production. PHASE II: Procure or produce initial batches of powder of downselected candidate alloys and manufacture representative laboratory test coupons. Test such coupons in accordance with test plans and determine level of agreement of material performance with predictions. Refine and optimize the alloy composition based on experimental results. Conduct manufacturing assessments to determine statistical parameters for quality and repeatability. Provide the test data to the Government along with preliminary cost, initial raw material sourcing, and schedule projections for pilot-scale powder production. PHASE III DUAL USE APPLICATIONS: Develop or transition the technology to pilot-scale feedstock production. Advance maturity of the AM process for these feedstocks, providing data on quality and repeatability of the both production and printing processes. Manufacture representative components for hypersonic or propulsion applications. REFERENCES: Gradl, P.; Mireles, O.R.; Katsarelis, C.; et al. Advancement of Extreme Environment Additively Manufactured Alloys for Next Generation Space Propulsion Applications. Acta Astronautica 2023, 211, 483-497. Pollock, T.M.; Clarke, A.J.; Babu, S.S. Design and Tailoring of Alloys for Additive Manufacturing. Metallurgical and Materials Transactions A 2020, 51, 6000-6019. Bose, A.; Schuh, C.A.; Tobia, J.C.; et al. Traditional and Additive Manufacturing of a New Tungsten Heavy Alloy Alternative. International Journal of Refractory Metals and Hard Materials 2018, 73, 22-28. Wang, X.; Xiong, W. Uncertainty Quantification and Composition Optimization for Alloy Additive Manufacturing through a CALPHAD-Based ICME Framework. NPJ Computational Materials 2020, 6, 188. KEYWORDS: Additive Manufacturing; Refractory Alloys; Integrated Computational Materials Engineering; Alloy Development
