Additive Manufacturing: Alloy Design to Develop New Feedstock Materials: Session II
Sponsored by: TMS: Additive Manufacturing Committee, TMS: Alloy Phases Committee
Program Organizers: Joseph McKeown, Lawrence Livermore National Laboratory; Aurelien Perron, Lawrence Livermore National Laboratory; Manyalibo Matthews, Lawrence Livermore National Laboratory; Christian Leinenbach, Empa, Swiss Federal Laboratories for Materials Science and Technology; Peter Hosemann, University of California, Berkeley
Wednesday 2:00 PM
November 4, 2020
Room: Virtual Meeting Room 4
Location: MS&T Virtual
Session Chair: Peter Hosemann, UC Berkeley; Aurelien Perron, LLNL
2:00 PM
3D Characterization of Cracks Formed in “Weldable” AA6061 and Implications for Alloy Design: Giuseppe Del Guercio1; Graham McCartney1; Nesma Aboulkhair1; Chris Tuck1; Marco Simonelli1; 1University of Nottingham
Solidification cracking is one of the major issues in the development of Laser-Powder Bed Fusion (L-PBF) of high strength Al-alloys. Weldability and cracking indices developed for processes where single heating/cooling profiles are imposed present shortcomings in predicting cracking behaviour during L-PBF - where materials experience multiple thermal cycles. In this talk, we investigate the origins of the cracking phenomena in the “weldable” aluminium alloy AA6061, to expose the merits and limitations of weldability indices in the context of L-PBF. The cracks formed in printed AA6061 and AA6061+Si (to mimic the influence of typical welding fillers) are characterised in 3D using a plasma FIB-FEGSEM to understand the effects of elemental segregation, crystallographic texture and dendrite morphology on the cracking phenomena. Such fundamental understanding is of paramount importance and will be discussed in relation to a newly proposed alloy design strategy for high strength aluminium alloys for L-PBF.
2:20 PM
Mechanical Alloying of Feedstock Powder for Additive Manufacturing by Selective Laser Melting: Aluminum Alloy Matrix Composites: Ethan Parsons1; 1MIT Lincoln Laboratory
Ceramic-reinforced metal matrix composites (MMCs) are attractive materials for high-value defense and commercial components, but fabrication with MMCs is presently difficult, costly, and limited to components with simple geometries. Additively manufacturing particulate MMCs with selective laser melting (SLM) would be an ideal method, but the laser consolidation of these materials has been largely unsuccessful in matching the properties of conventionally produced MMCs. The challenges include spreading the heterogeneous powder, distributing the ceramic particles, and forming a strong bond between the metal and the ceramic. Here, we use mechanical alloying to fabricate composite powders with morphology tuned for SLM process conditions. Using SLM, we achieve nearly fully dense consolidation of these powders and thereby demonstrate the potential for MMC feedstock powders to be produced with scalable, cost-effective methods.
2:40 PM Invited
An Interdisciplinary Approach for Alloy Design for Additive Manufacturing: Raymundo Arroyave1; 1Texas A&M University
To date, the vast majority of work on metal AM has been framed in terms of the need to tune processing conditions in order for a specific conventional alloy, such as stainless steel, Ni-based super alloys, aluminum alloys, etc. This approach often overlooks the fact that historically, every engineering alloy has always been designed having a specific synthesis/processing route in mind. In this talk, I will present some recent work trying to address some of the challenges associated with the design of feedstock for AM. In order to design anything, one must have first a design metric and I thus revisit the concept of an alloy "printability". I then proceed to discuss what types of intrinsic (and extrinsic) materials attributes are amenable to optimization for printability. I finalize the talk by providing a couple of examples of 'co-design', in which alloy performance and printability have been taken into account.
3:10 PM
CALPHAD Informed Design of Rare-earth Containing Alloys for Additive Manufacturing: Emily Moore1; 1Lawrence Livermore National Laboratory
The addition of rare-earth elements (REE), specifically cerium is of interest to improve the mining economics of Nd, Pr, Sm, etc., which are widely used in clean energy technology. Thermochemical models using the CALPHAD (CALculation of PHAse Diagrams) method aid in alloy design for additive manufacturing by predicting the phase-behavior of multi-component systems to achieve the desired chemical makeup of an alloy. Thermodynamic databases to investigate Al-Ce alloys and Ce-Co alloys have been developed and include the following elements, respectively : Al-Ce-Cu-Fe-La-Mg-Ni-Si-Zn-Zr and Ce-Co-Cu-Fe-La. The models are applied to design alloys with within specified composition ranges and include relevant phases that are empirically known to provide strengthening properties.Prepared by LLNL under Contract DE-AC52-07NA27344. Research supported by CMI, an Energy Innovation Hub funded by the U.S. DOE, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.
3:30 PM
Development of Oxidation Resistant Multi-Principle Element Alloys Applied with Additive Manufacturing: Jose Loli1; Yining He1; Amish Chovatiya1; Zachary Ulissi1; Bryan Webler1; Jack Beuth1; Maarten De Boer1; 1Carnegie Mellon University
Multi-Principle Element Alloys (MPEAs) are shown to have exceptional properties and demonstrate promise as a new methodology for alloy discovery. We focus on screening alloys that can be deposited as coatings by additive manufacturing and will further exhibit high oxidation resistance. To determine candidate MPEAs, we simulated CALPHAD data of 5 and 4 element equimolar combinations from a 12-element palette to screen alloys that were single phase at the solidus. Because oxidation behavior is difficult to predict for MPEAs, we made use of a regression model fitted on experimental data found in literature. We then arc-melted, characterized, and further screened candidate alloys based on oxidation behavior. To determine their compatibility with additive manufacturing, cracking susceptibility was tested with single laser track experiments. Given the complex interplay between oxidation resistance, MPEAs, and additive manufacturing, we expect our balanced modeling, machine learning, and experimental approach will lend insight in future MPEA development.