Rapid Material Development for Lightweight Additive Manufactured (AM) Structures and Repairs

Navy STTR 20.B - Topic N20B-T026

Naval Air Systems Command (NAVAIR) - Ms. Donna Attick [email protected]

Opens: June 3, 2020 - Closes: July 2, 2020 (12:00 p.m. ET)

 

 

N20B-T026       TITLE: Rapid Material Development for Lightweight Additive Manufactured (AM) Structures and Repairs

 

RT&L FOCUS AREA(S): General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platform, Materials, Weapons

 

OBJECTIVE: Develop a novel high-performance alloy for structural components and repairs capable of being produced by Additive Manufacturing (AM), and that exhibits high strength, low density, high corrosion resistance, and improved process-ability traits. Tools such as integrated computational materials engineering (ICME), AM, accelerated testing concepts, and data mining to accelerate the development and qualification of the alloy should be used.

 

DESCRIPTION: Magnesium (Mg) is the lightest structural metal with a density that is 35% lower than aluminum, making it a prime candidate for light weighting in the aerospace and automotive industries [Ref 1]. The helicopter industry has capitalized on the low density of Mg in the past, mainly in transmission casings (e.g., H-60, H-53) [Ref 2]. However, most applications of Mg are non-structural or semi-structural due to the limited mechanical properties of legacy Mg alloys. Mg’s process-ability issues (i.e., flammability) and poor corrosion resistance further restricts the use of Mg on U.S. Navy (USN) aircraft [Ref 2]. In fact, many components manufactured from legacy Mg alloys corrode relatively quickly in-service, which leads to unscheduled maintenance to repair or replace those components. The various forms of AM can provide opportunities to repair those components or to build one-off replacements for them, which could help reduce life-cycle maintenance time and costs for USN aircraft. However, the legacy Mg alloys are currently limited to wrought/cast product forms due to Mg’s high oxygen affinity and low melting/evaporation points, which make it difficult to process with AM [Refs 2-4].

 

A novel high-performance alloy for structural components and repairs that possesses high strength, low density, high corrosion resistance, and improved process-ability traits is sought. To decrease development time, an ICME framework should be used to design the alloy. The alloy should be designed to be produced in powder form, and to be processed using powder-based AM to further reduce development time [Ref 5]. Flammability and oxidation should be key design considerations to improve the process-ability of the alloy by reducing the risk of ignition during production and post-processing. The alloy should have a density comparable to that of a magnesium alloy (less than 0.0838 lb/in^3) and mechanical properties that meet or exceed the following:

·        Specific Ultimate Strength: 700 ksi /(lb/in^3)

·        Specific Yield Strength: 500 ksi /(lb/in^3)

·        Ultimate Elongation: 8%.

 

The alloy should have improved corrosion resistance and improved fatigue resistance in comparison to legacy Mg alloys such as AZ31 or WE43. Experimentally show the feasibility of the alloy design, and once the material composition has been refined, coupons should be produced and tested to verify the performance of the new, lightweight alloy.

 

The results of this STTR effort could reduce lifecycle maintenance and costs for USN aircraft: the alloys created could be an alternative to conventional magnesium alloys, albeit with superior corrosion resistance and better process-ability for component maintenance/rework. This alloy could also reduce the logistical footprint of USN aircraft by providing the capability to replace cast Mg components with AM equivalent components without the high costs and lead-times associated with foundries. A new high-strength, lightweight alloy that is capable of being produced with AM would allow newly designed components to have increased structural efficiency (i.e., higher strength to weight ratios), and would enable the production of ultra-lightweight topology optimized parts.

 

PHASE I: Formulate a novel high-performance alloy using ICME tools and produce a sample batch of the alloy in powder form. Process the demonstration powder in a powder-based AM system and establish the feasibility of the alloy design by generating limited test data, such as static/fatigue strength data (per ASTM E8 and ASTM E466, respectfully), microstructural characterization (per ASTM E3, ASTM E112, and ASTM E407). The Phase I effort will include prototype plans to be developed under Phase II.

 

PHASE II: Refine the alloy composition through an iterative approach that includes modeling, AM fabrication, and testing of ASTM E8/E466 [Refs 6,7] coupons and prototype parts. Initiate the development of the material properties database for an optimized alloy design. Develop an optimized heat-treatment for the alloy if heat treatment is required to achieve desired properties.

 

PHASE III DUAL USE APPLICATIONS: Fully develop the design allowable database for the high-performance alloy. Demonstrate and validate the performance of the new material through component testing in a service environment. Transition the newly developed alloy for use in the fabrication of USN and commercial aircraft structural components.

 

The high-performance alloy developed in this effort could be directly transitioned into applications for both commercial aerospace and automotive industries. Beyond aircraft applications, the missile and satellite industries are long-time users of magnesium components and could also benefit from an improved lightweight structural alloy. This effort would also produce the groundwork needed to develop additional AM-tailored materials for other commercial applications. For example, an excellent fit for an AM-capable magnesium is the biomedical industry. Magnesium offers properties that makes it suitable as a biodegradable metal [Ref 3], which would be useful in applications such as repairing fractured bones.

 

REFERENCES:

1. Luo, A. A. “Application of Computational Thermodynamics and Calphad in Magnesium Alloy Development.” 2nd World Congress on Integrated Computational Materials Engineering (ICME), 2013, pp. 3-8. https://link.springer.com/chapter/10.1007/978-3-319-48194-4_1

 

2. Czerwinski, F. “Controlling the Ignition and Flammability of Magnesium for Aerospace Applications.” Corrosion Science, September 2014, pp. 1-16. https://www.sciencedirect.com/science/article/pii/S0010938X14002182  

 

3. Zumdick, N., Jauer, L., Kutz, T. & Kersting, L. “Additive Manufactured WE43 Magnesium: A Comparative Study of the Microstructure and Mechanical Properties with those of Powder Extruded and As-Cast WE43.” Materials Characterization, Volume 147, January 2019, pp. 384-397. https://www.sciencedirect.com/science/article/pii/S1044580318324689   

 

4. Pawlak, A., Rosienkiewicz, M. & Chlebus, E. “Design Experiments Approach in AZ31 Powder Selective Laser Melting Process Optimization.” Archives of Civil and Mechanical Engineering, Volume 17, Issue 1, January 2017, pp. 9-18. https://www.sciencedirect.com/science/article/abs/pii/S1644966516300917  

 

5. Dietrich, S., Wunderer, M., Huissel, A. & Zaeh, M. “A New Approach for a Flexible Powder Production for Additive Manufacturing.” Procedia Manufacturing, Volume 6, December 2016, pp. 88-95. https://www.sciencedirect.com/science/article/pii/S2351978916301482  

 

6. “ASTM Standard E8/8a 16: Standard Test Methods for Tension Testing of Metallic Materials." ASTM International: West Conshohocken, PA, 2016. https://www.astm.org/search/fullsite-search.html?query=Standard%20Test%20Methods%20for%20Tension%20Testing%20of%20Metallic%20Materials&  

 

7. “ASTM Standard E466 15: Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials." ASTM International: West Conshohocken, PA, 2015. https://www.astm.org/Standards/E466  

 

8. “ASTM Standard E3-11 2017: Standard Guide for Preparation of Metallographic Specimens." ASTM International: West Conshohocken, PA, 2017. https://www.astm.org/Standards/E3.htm  

 

9. “ASTM Standard E11213:Standard Test Methods for Determining Average Grain Size." ASTM International: West Conshohocken, PA, 2014, https://www.astm.org/Standards/E112  

 

10. “ASTM Standard E407(2015)e1:Standard Practice for Microetching Metals and Alloys." ASTM International: West Conshohocken, PA, 2015. https://www.astm.org/Standards/E407

 

KEYWORDS: Additive Manufacturing, AM, Powder, Integrated Computational Materials Engineering, ICME, Magnesium, Material, Structure

 

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