Abstract
Readily available high strength Al-alloys for laser power bed fusion (LPBF) typically require post-processing such as mechanical working or heat treatment to evolve strengthening phases. Through the calculation of phase diagrams (CALPHAD) and a method based on Scheil solidification, the Al-8 wt%Ce-10 wt%Mg alloy was evaluated for LPBF to be microstructurally favorable to yield components with full volumetric density, without the need for post-processing. Through an exhaustive LPBF parametric study, documentation of defects was performed for the use of a wide range of laser power and scan speed combinations, i.e., varying the energy density, followed by microstructural characterization with X-ray diffraction, optical and electron microscopy, and mechanical testing with both Vickers hardness and quasi-static uniaxial tension. Overall, defects were observed with use of high and low laser powers and scan speeds, but a processing window for LPBF was observed at both high and low laser powers, where > 99% volumetric density was achieved. Besides defects, decreasing the scan speed, i.e., increasing the energy density, resulted in decreases in the concentration of Mg, down to a maximum of 4.5 wt% due to vaporization. Moreover, a decrease in Mg led to a lower Vickers hardness, attributed to a decrease in the solid solutioning of Mg in the α-Al matrix. Samples selected for tensile mechanical testing were produced with a LPBF laser power of 200 W traversing at 800 mm/s, which yielded a density > 99% and Mg concentration of approximately 7 wt%. A yield strength and ultimate tensile strength of 377 and 468 MPa, respectively, was found for those produced with the power of 200 W. However, the ductility of the alloy was less than 2% elongation at failure. A fine (< 1 µm) sub-grain cellular solidification structure was found distributed throughout the α-Al matrix, with ribbons of the eutectic Al11Ce3 intermetallic distributed along the intercellular boundaries. The high strengths achieved in this alloy were attributed to contribution from Orowan dislocation looping of the Al11Ce3 phase, the high degree of solid solutioning of Mg in the α-Al matrix, and cellular boundary strengthening due to impeding dislocation movement.
| Original language | English |
|---|---|
| Article number | 102657 |
| Journal | Additive Manufacturing |
| Volume | 52 |
| DOIs | |
| State | Published - Apr 2022 |
| Externally published | Yes |
Funding
Holden Hyer: Methodology (Development or design of methodology; creation of models), Software (N.A., Programming, software development; designing computer programs; implementation of the computer code and supporting algorithms; testing of existing code components). Formal analysis (Application of statistical, mathematical, computational, or other formal techniques to analyze or synthesize study data). Investigation (Conducting a research and investigation process, specifically performing the experiments, or data/evidence collection). Data curation (Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it is necessary for interpreting the data itself) for initial use and later reuse). Writing – original draft (Preparation, creation and/or presentation of the published work, specifically writing the initial draft (including substantive translation)). Writing – review & editing (Preparation, creation and/or presentation of the published work by those from the original research group, specifically critical review, commentary or revision – including pre-or postpublication stages). Visualization (Preparation, creation and/or presentation of the published work, specifically visualization/ data presentation). Abhishek Mehta: Methodology (Development or design of methodology; creation of models), Software (N.A., Programming, software development; designing computer programs; implementation of the computer code and supporting algorithms; testing of existing code components). Validation (Verification, whether as a part of the activity or separate, of the overall replication/ reproducibility of results/experiments and other research outputs). Formal analysis (Application of statistical, mathematical, computational, or other formal techniques to analyze or synthesize study data). Investigation (Conducting a research and investigation process, specifically performing the experiments, or data/evidence collection). Data curation (Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it is necessary for interpreting the data itself) for initial use and later reuse). Kevin Graydon: Methodology (Development or design of methodology; creation of models), Software (N.A., Programming, software development; designing computer programs; implementation of the computer code and supporting algorithms; testing of existing code components). Validation (Verification, whether as a part of the activity or separate, of the overall replication/ reproducibility of results/experiments and other research outputs). Formal analysis (Application of statistical, mathematical, computational, or other formal techniques to analyze or synthesize study data). Investigation (Conducting a research and investigation process, specifically performing the experiments, or data/evidence collection). Data curation (Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it is necessary for interpreting the data itself) for initial use and later reuse). Nemanja Kljestan: Formal analysis (Application of statistical, mathematical, computational, or other formal techniques to analyze or synthesize study data). Investigation (Conducting a research and investigation process, specifically performing the experiments, or data/evidence collection). Data curation (Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it is necessary for interpreting the data itself) for initial use and later reuse). Visualization (Preparation, creation and/or presentation of the published work, specifically visualization/ data presentation). Marko Knezevic: Resources (Provision of study materials, reagents, materials, patients, laboratory samples, animals, instrumentation, computing resources, or other analysis tools). Supervision (Oversight and leadership responsibility for the research activity planning and execution, including mentorship external to the core team). Project administration (Management and coordination responsibility for the research activity planning and execution). Funding acquisition (Acquisition of the financial support for the project leading to this publication). David Weiss: Conceptualization (Ideas; formulation or evolution of overarching research goals and aims). Resources (Provision of study materials, reagents, materials, patients, laboratory samples, animals, instrumentation, computing resources, or other analysis tools). Brandon McWilliams: Resources (Provision of study materials, reagents, materials, patients, laboratory samples, animals, instrumentation, computing resources, or other analysis tools). Project administration (Management and coordination responsibility for the research activity planning and execution). Funding acquisition (Acquisition of the financial support for the project leading to this publication). Kyu Cho: Conceptualization (Ideas; formulation or evolution of overarching research goals and aims). Resources (Provision of study materials, reagents, materials, patients, laboratory samples, animals, instrumentation, computing resources, or other analysis tools). Project administration (Management and coordination responsibility for the research activity planning and execution). Funding acquisition (Acquisition of the financial support for the project leading to this publication). Yongho Sohn: Conceptualization (Ideas; formulation or evolution of overarching research goals and aims). Methodology (Development or design of methodology; creation of models), Software (N.A., Programming, software development; designing computer programs; implementation of the computer code and supporting algorithms; testing of existing code components). Resources (Provision of study materials, reagents, materials, patients, laboratory samples, animals, instrumentation, computing resources, or other analysis tools). Data curation (Management activities to annotate (produce metadata), scrub data and maintain research data (including software code, where it is necessary for interpreting the data itself) for initial use and later reuse). Writing – original draft (Preparation, creation and/or presentation of the published work, specifically writing the initial draft (including substantive translation)). Writing – review & editing (Preparation, creation and/or presentation of the published work by those from the original research group, specifically critical review, commentary or revision – including pre-or postpublication stages). Visualization (Preparation, creation and/or presentation of the published work, specifically visualization/ data presentation). Supervision (Oversight and leadership responsibility for the research activity planning and execution, including mentorship external to the core team). Project administration (Management and coordination responsibility for the research activity planning and execution). Funding acquisition (Acquisition of the financial support for the project leading to this publication). This research was sponsored, in part by the Office of Naval Research (No. N00014-17-1-2559) and in part by the DEVCOM Army Research Laboratory (No. W911NF1720172). The views, opinions, and conclusions made in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Office of Naval Research or the DEVCOM Army Research Laboratory or the US Government. The US Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.
Keywords
- Al-alloy
- CALPHAD
- Cracking susceptibility
- Laser powder bed fusion
- Strengthening mechanisms
- Tensile properties
