Additive Manufacturing of Metals

Summary

This project enables new pathways for innovative materials design of additively manufactured metal alloys though a foundation of materials science, measurement science, and data science that focuses on localized and in situ measurements of process-structure-property-performance relationships at relevant time and length scales.

Description

Photograph of metal AM parts used for AM Bench 2018 (top) and a microstructure comparison (bottom) between wrought (left) and stress relieved AM (right) IN625

The Additive Manufacturing of Metals Project, which has participants from multiple groups and divisions, and has three primary objectives:

• Develop and utilize novel local and in situ measurement capabilities for establishing AM mechanisms responsible for processing and post-processing pathways in AM applications.
• Establish mechanisms leading to novel processing and post-processing pathways for AM applications while providing data and models to enable the development of optimized heat treatments and alloys.
• Provide curated world-leading measurement data and metadata for developing and improving modeling and simulation capabilities that drive AM design and support qualification, certification, reliability, and reproducibility.

Major Current Activities

Processing-structure-property-performance measurements and models

• Use coupled measurements and thermo-kinetic modeling to complete development of heat treatments for AM 17-4PH
• Use coupled measurements and thermo-kinetic modeling to develop effective heat treatments for AM IN718 components in collaboration with the petroleum and natural gas industry. This work is part of a CRADA with Shell Oil Corporation.
• Use coupled high-speed measurements to explore the phase transformations of advanced AM aluminum alloys under build conditions.

Develop new in situ lab-based and synchrotron X-ray measurement capabilities for AM heat treatments and builds

• Develop new in-house directed energy deposition AM platform to explore novel processing methods incorporating magnetic fields and secondary laser heating sources.
• Provide unique high-speed deformation and heating data on AM 17-4 SS to support AM research including hybrid manufacturing.
• Develop and validate new magnetics-based measurements for determining the austenite phase fraction in AM 17-4PH.
• Work with staff at the Advanced Photon Source (APS) to develop, install, and test a new generation of the existing ultra-small-angle X-ray scattering (USAXS) instrument, providing enhanced capabilities for measuring thicker samples, a larger range of precipitate sizes (sub-nm to micrometers), internal elastic strains, crystallographic texture, and phases in situ during thermal processing of metal specimens.

Model validation

• Founded by the Additive Manufacturing of Metals project, the Additive Manufacturing Benchmark Series (AM Bench) is a NIST-led organization that provides a continuing series of AM benchmark measurements, challenge problems, and conferences with the primary goal of enabling modelers to test their simulations against rigorous, highly controlled additive manufacturing benchmark measurement data. AM Bench partners include researchers from 10 NIST divisions and 20 outside organizations. Complete AM Bench cycles were completed in 2018 and 2022. For detailed information on AM Bench, see www.nist.gov/ambench.    
• Work with AM Bench partners to organize, analyze, and publish all AM Bench 2022 datasets; continue to develop and deploy data management systems for curating and sharing all AM Bench data and metadata; hold AM Bench challenge problem workshops for all completed AM Bench challenge problems; publish all AM Bench measurement data sets; plan and execute future benchmark activities.
• Work with the Exascale Computing Project's AM use case (ExaAM) to develop and conduct measurements needed to guide and validate AM simulation codes currently in development for the first exa-scale high performance computing systems as they become available. The first such system, Frontier at ORNL, became available for our use on 4/3/2023.

  

  Distribution of elastic strains within an AM Bench additively manufactured IN625 bridge structure

Data management

• Work with NIST and external collaborators to develop and deploy comprehensive sample tracking and data management systems in support of AM Bench. Operational versions of all systems have been made public and serve as prototypes for broader data management within the Additive Manufacturing of Metals project and the Materials Science and Engineering Division.
  • AM Bench Website – Best source for information and data links concerning the AM Bench measurements, data, challenge problems, and conference series
  • NIST Public Data Repository (PDR) – primary access to all public AM Bench measurement data
  • Traditional publications in the journal Integrating Materials and Manufacturing Innovation, within the thematic section: AM-Bench 2022.  These AM Bench 2022 measurement articles are expected to become available in late 2023.
  • Measurement catalog – searchable data and metadata curation system.
  • SciServer – Free analysis and processing of large AM Bench data sets can be conducted directly on the data server using your own or provided codes. This avoids the need to download TBs of measurement data and provides easy analysis using a Jupyter notebook environment.  AM Bench data on SciServer is copied from the NIST PDR.
• AM Bench GitHub – AM Bench users will be able to share models and codes that can run on the AM Bench SciServer or at your home institution - development in progress.

Additional outside collaborations

• Computational Materials for Qualification and Certification (CM4QC) is an industry/government agency/university steering group that is working to Identify key considerations and enablers required to increase the airworthiness certifying authorities’ and the industry’s acceptance of the use of computational methods for Q&C of structural AM parts. We are a founding member and serve on the CM4QC leadership team. Partners include:
  • Industry - Boeing, GE Aviation, Honeywell, Howmet Aerospace, Lockheed Martin, Northrop Grumman, Pratt & Whitney, Sikorsky, Spirit Aerosystems, Textron Aviation
  • Research Institutes - Southwest Research Institute
  • Government agencies - NIST, NASA Langley, Federal Aviation Administration, Air Force Research Laboratory, Army Aviation, Naval Air Systems Command, Oak Ridge National Laboratory, Sandia National Laboratory
  • Universities - Carnegie Mellon, Northwestern, Penn State, University of Texas San Antonio

Anticipated Outputs of Project

• Effective heat treatments and alloy modifications for nitrogen-atomized AM 17-4PH developed and disseminated.
• Alloy design and modification data and analyses, covering cooling rate, microstructure, and mechanical properties, will be disseminated for directed energy deposition (DED) and/or LPBF-built materials, including Ti alloys and 17-4PH.
• Corrosion and stress corrosion cracking data and analyses will be disseminated for AM IN625, 17-4PH, and 718.
• New generation of the existing APS USAXS instrument will be built, fielded, tested, and made available for general users. New capabilities for this project will include greater X-ray penetration, improved q-resolution, and elastic strain and texture measurement capabilities for in situ microstructure evolution measurements during post build heat treatments. Most instrumentation is complete, tested, and ready for the upcoming major APS upgrade to be completed in spring of 2024.
• Coordinated additive manufacturing measurements for metals and polymers by 10 NIST divisions and 20 external organizations have been completed as part of AM Bench 2022. Data are currently being analyzed, organized, curated, published, and shared with the AM community using the data management systems described above.  
• Four dimensional (space and time) digital twin data sets developed and disseminated including multiple in situ data streams during the build and positionally synced XRCT and serial section microstructure data.  Custom codes will enable user friendly data mining.

Major Accomplishments

Founded and Lead the Continuing Additive Manufacturing Benchmark Series (2015 - present)

• First round of metal and polymer benchmarks completed 2018
• AM Bench 2018 conference held June 18-21, 2018
• Currently, staff from 11 NIST divisions and 19 outside organizations are working together toward AM Bench 2022
• www.nist.gov/ambench; ambench.nist.gov

Published a computational framework for developing new AM specific alloys (2020)

• Used a  combination of additive manufacturing-computational fluid dynamics (AM-CFD) and calculation of phase diagram (CALPHAD) to predict location specific β→α phase transformation for a new Ti-Al-Fe-based titanium
• Successfully validated model predictions using spatially resolved synchrotron-based X-ray diffraction
• Demonstrated that this framework can be applied for rapid and comprehensive evaluation of location-specific thermal history, phase, microstructure, and properties for new AM titanium alloy development.

Uncovered Underlying Mechanism for Difference Between Additive Manufactured and Wrought IN625 (2017-2018)

• Discovered δ-phase in stress relieved AM IN625 (2017)
• Successfully modeled and validated growth of δ-phase in AM IN625 (2018)
• Developed time-temperature-transformation diagram for AM IN625 and new suggested stress relief heat treatment (2018)

Demonstrated that AM-produced 17-4PH stainless steel can have improved corrosion resistance over wrought material  (2017)

• Potentiodynamic scans evaluated pitting behavior of wrought and several AM SS17-4 materials.
• Electrochemical measurements determined that nitrogen retained from atomization can significantly enhance the corrosion resistance of AM SS17-4
• Determined that, with proper heat treatment, the environmental cracking resistance of AM-processed IN625 is comparable to wrought material