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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

Build plate of additively manufactured (AM) metal parts with microstructure comparison between wrought and AM material

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:

  • Provide data and models to enable the development of new heat treatments and new alloys for AM applications.
  • Develop and utilize new material measurement capabilities for probing microstructural evolution during the build and post-build thermal processing, and for probing material properties and performance under relevant conditions.
  • Provide curated world-leading measurement data and metadata that AM modelers world-wide can use for guidance and validation.

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.
  • 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

  • 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.
  • The APS has an AM instrument that allows in situ high-speed imaging of laser melt pools. We are working with our Engineering Laboratory and Physical Measurement Laboratory collaborators and external partners to upgrade this instrument for full calibration and use for both science studies and cross-comparisons with NIST AM instruments.
    Figure 1: Video showing laser melting a metal surface and with a graph showing how much laser radiation is absorbed.
    Figure 1: An example of simultaneous high-speed X-ray radiography and time-dependent absorption data.

Model  validation

  • Work with AM Bench partners to organize and complete all AM Bench 2022 builds and measurements for metals and polymers; develop and deploy data management systems for curating and sharing all AM Bench data; develop and share AM Bench 2022 modeling challenge problems; collect and evaluate all AM Bench 2022 modeling challenge problem submissions; publish all AM Bench measurement data sets; organize and hold the AM Bench 2022 conference to be held Aug. 15-18, 2022 in Bethesda, MD.
  • 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 when they become available.
    Image of additively manufactured bridge specimen showing a color map of residual elastic strains
    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.  These systems will be a prototype for broader data management within the Additive Manufacturing of Metals project and the Materials Science and Engineering Division. 
  • Implement server-side analysis of large, multimodal data sets, with the eventual goal of implementing full digital twin integration of all build data, in situ measurements, XRCT characterization, and 3D microstructure from AFRL serial sectioning. 

Anticipated Outcomes/Impacts 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.
  • Fully calibrated, in situ imaging and diffraction measurements for additive manufacturing of metals developed in an MML-led partnership with EL, PML and the APS and made available to general users.
  • Coordinated additive manufacturing measurements for metals and polymers by 11 NIST divisions and 19 external organizations will be organized, completed, analyzed, curated, published, and shared with the AM community through AM-Bench 2022. 
  • 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/ambenchambench.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
    Created February 24, 2022, Updated June 24, 2022