Additive Manufacturing: Materials Design and Alloy Development II: Alloy Design- Aluminum Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Behrang Poorganji, Morf3d; James Saal, Citrine Informatics; Orlando Rios, University of Tennessee; Hunter Martin, HRL Laboratories LLC; Atieh Moridi, Cornell University
Tuesday 8:30 AM
February 25, 2020
Room: 6F
Location: San Diego Convention Ctr
Session Chair: Hunter Martin, HRL Laboratories
8:30 AM Invited
Inoculant Enabled Alloy Design for High Strength Aluminum: Mark O'Masta1; Julie Miller1; Jacob Hundley1; Brennan Yahata1; Tobias Schaedler1; John Martin1; 1HRL Laboratories LLC
Additive manufacturing of many high strength alloys is generally precluded by their susceptibility to hot-crack. This phenomena is a result of the high thermal gradients seen in powder fusion methods, which create the conditions for dendritic growth and the resulting inter-dendritic cavitation and tearing/cracking at high solid fractions. Here we discuss alloy design, with particular attention on element additions through nano-functionalization, to modify the thermodynamic driving forces and leverage the unique thermal conditions in AM. Through experimental and numerical studies, we will show the ability to print what would otherwise be a hot-crack susceptible alloy tailored to the unique conditions of AM (e.g., SLM, DED) and discuss the role of solute additions on printablility and the ultimate performance of the alloy.
9:00 AM Cancelled
Evaluation of Hot Tearing During Laser Surface Melting of Aluminium Alloy 7150 with Rare Earth Additions: Michael Benoit1; Suming Zhu2; Trevor Abbott3; Mark Easton1; 1School of Engineering, RMIT University; 2RMIT University; 3Magontec Ltd
Susceptibility to hot tearing is a limitation for additive manufacturing of high strength Al alloys. The effectiveness of rare earth (RE) additions to AA7150 to reduce hot tearing during laser surface melting is investigated in this study. Cracking was observed in at least one cross section for nearly all experimental conditions, although the cracks in the base alloy appeared to be smaller than those in the samples with RE additions. Elemental mapping of the interdendritic phases at the crack tips was in agreement with solidification simulation phase predictions. The hot tearing susceptibility of the alloys was calculated from solidification simulations, and was found to be sensitive to the limits used in the calculation; RE additions were predicted to reduce hot tearing for certain conditions, but increased the susceptibility for other conditions. From the experimental results, it is concluded that RE additions are not effective in reducing hot tearing in AA7150.
9:20 AM
Enabling Additive Manufacturing of High Temperature Aluminum Alloys Utilizing Grain Refiners: Julie Miller1; 1HRL Laboratories LLC
The ability to 3D print aluminum alloys is an area of high interest due to the wide use of aluminum in the aerospace, automotive, and engineering industries. This range of applications requires an equally broad array of material properties that can be achieved through the various series of aluminum alloys. Grain refiners have been previously shown to be a viable technique for printing crack-free, high-strength aluminum 7075. This talk will focus on this technique’s successfully application to 2xxx series, high temperature aluminum alloys. This work demonstrates the success of grain refiners in printing both high strength and high temperature alloys, with a specific focus on the achieved mechanical properties. Attention is also paid to the expansion of the design space around aluminum alloy 3D printing made possible by this technology including lower cost alloys and alloys designed specifically for additive manufacturing.
9:40 AM
Development of High Thermal Conductivity Aluminum Alloys Suitable for Additive Manufacturing: Andrew Bobel1; John Martin2; Julie Miller2; Brennan Yahata2; Jacob Hundley2; Justin Mayer2; 1General Motors; 2HRL Laboratories
The addition of functionalizing additives on the printability, microstructure, and strength of pure aluminum powder was studied. Printability of pure Al via laser powder bed fusion is hindered by epitaxial growth of long columnar grains during the additive manufacturing process which lead to severe cracking and part failure thereby. Significant reduction in grain size, elimination of columnar grain growth, and improved printability has been previously demonstrated via the functionalization of 7075 aluminum additive powder. Here, we explore the addition of various nano- and micron-sized functionalizing additives to pure Al powder to similarly inhibit columnar grain growth, while maintaining the desired high thermal conductivity of pure Al. The additives effects on grain structure, thermal conductivity, and strength were explored in printed specimens and compared to those of printed pure Al. This work lays the foundation for the development of functionalized nearly pure aluminum with high thermal conductivity suitable for additive manufacturing.
10:00 AM
Addition of Nano-particles During Additive Manufacturing of AlSi10Mg Alloy: Catherine Dolly Clement1; Abu Syed Kabir1; 1Carleton University
One of the major problems associated with additive manufacturing (AM) of metallic parts is the formation of columnar/directional grains that gives a significant mechanical anisotropy in the structural part. Columnar grains form due to multiple melting and solidification cycles during AM process and also due to the lack of suitable nucleation sites, where new grains can form dynamically if the conditions are met. Addition of carefully chosen nano-particles (~1 vol%) during the AM process may work as nucleation sites by a mechanism called particle stimulated nucleation (PSN). In this study, cubic boron nitride nanoparticles have been added during the additive manufacturing of AlSi10Mg alloy. Microstructural evaluation was investigated by optical and scanning electron microscopes and the phases were identified by X-ray diffraction (XRD) and Electron Probe Micro Analyzer (EPMA).
10:20 AM Break
10:35 AM Invited
Selective Laser Melting of Elemental Powder Blends to Manufacture Precipitation and Oxide-dispersion Strengthened Al Alloys: Jennifer Glerum1; Christoph Kenel1; David Dunand1; 1MSE, Northwestern University
Oxide-dispersion strengthened parts have been manufactured via AM for energy applications (i.e. gas and steam turbines) from pre-alloyed powders. Using elemental powder blends expands the design space and reduces the cost and compositional limitations associated with pre-alloyed powders. However, the elemental powders need to be fully melted or reacted to form the desired alloy. In this talk, elemental blends of aluminum, transition metals, and aluminum oxide solidified via selective laser melting (SLM) to create precipitation- and oxide-dispersion strengthened (PODS) alloys and their in-situ and ex-situ characterization will be discussed. The melt pool behavior and phase evolution was studied using in-situ high-speed imaging and in-situ diffraction on single line scans (Advanced Photon Source) to cover a wide range of processing parameters and blend compositions. Suitable alloys and reduced processing parameter windows are then selected for in-situ diffraction during full builds (Swiss Light Source).
11:05 AM
Feedstock Material Composition Modifications for Improved Processability by Laser Powder-bed Fusion: A Case Study on Aluminium: Nesma Aboulkhair1; Marco Simonelli1; Ehab Salama2; Graham Rance1; Nigel Neate1; Christopher Tuck1; Amal Esawi2; Richard Hague1; 1University of Nottingham; 2The American University in Cairo
The interest in metal additive manufacturing by laser powder-bed fusion (L-PBF) is ever-growing, with the amount of work done on processing aluminium alloys increasing exponentially. However, the work on pure aluminium is quite limited since the material was shown to be difficult-to-process by L-PBF for its relatively high reflectivity in the range of wavelengths used in the process. In this work, we are proposing an approach to improve the material’s processability by adding multi-walled carbon nanotubes to the Al feedstock and benefit from their high laser absorptivity. Besides improving the processability, a range of reinforcements formed in the produced material that were studied using a range of microstructural and mechanical characterisation techniques. The powder feedstock was prepared using various approaches (simple mixing, satelliting, and high energy ball milling) to investigate the role of the mixing technique on the quality and properties of the fabricated parts.
11:25 AM
Effect of Zr Alloying Content on the Printability and Property of Laser Powder Bed Fused Aluminum 5083 Alloys: Le Zhou1; Holden Hyer1; Sharon Park1; George Benson1; Yongho Sohn1; 1University of Central Florida
As many conventional aluminum alloys behave poorly for laser powder bed fusion (LPBF), novel aluminum alloys with improved printability and property are desired for LPBF. One design strategy is to develop LPBF aluminum alloys with refined grain structures via alloying with Zr. AA5083 and AA5083 modified with 0.7wt.% and 1.0wt.% of Zr have been manufactured by LPBF using gas atomized powders. Parametric investigation showed that the porosity development was similar for all alloys at various processing parameters. However, the Zr addition helped to eliminate/reduce the amount of cracks observed in as-built samples. Furthermore, the higher Zr concentration expanded the processing window and improved the printability. The microstructure was significantly refined in the as-built Zr-modified AA5083 alloys due to the in-situ grain refining associated with the formation of Al3Zr. Tensile tests of as-built and heat-treated Zr-modified AA5083 alloys demonstrated that the Zr also contributed to the strength increase through precipitation strengthening.
11:45 AM
A20X and AlSi10Mg Aluminium Alloys: A Comparison: Richard Selo1; Ian Maskery1; Ian Ashcroft1; Christopher Tuck1; 1University of Nottingham
This work describes the development and characterisation of a high strength aluminium copper alloy previously known to have poor processability with Laser Powder Bed Fusion (LPBF). A20X, a version of A201 casting alloy with modified composition to reduce hot cracking has been studied. Process parameter optimisation is investigated to achieve low porosity (<0.05%). This high-strength alloy is compared to AlSi10Mg, the go-to aluminium alloy for LPBF, in terms of microstructure and hardness and its advantages and inconvenient are discussed.
12:05 PM
Prospects of Application of New Aluminum Alloys for Selective Laser Melting: Daria Daubarayte1; Mann Viktor2; Alexander Krokhin2; Dmitriy Ryabov2; Vakhromov Roman1; Korolev Vladimir1; Alexander Seferyan1; 1Light Materials and Technologies Institute; 2RUSAL Management
In recent years, the role of additive technologies in manufacturing functional details from aluminium alloys for different industries has been growing incredibly fast. Moreover, the effect of fast crystallization and complex alloying makes it possible to achieve improved level of mechanical properties. In the present work the application for new high-strength and temperature-resistant aluminium materials instead of traditional castings and forged parts is suggested. Results of mechanical tests of new high-strength RS-320,RS-553 and RS-507 alloys are shown. The advantages of precipitations, forming in structure during heat treatment and its’ influence on the level of mechanical properties are described. The principles of chemical compositions adaptation of heat-resistant RS-230 and RS-390 alloys for selective laser melting process are presented. Structure formation features of synthesized materials before and after heat treatment are shown. The opportunities to use bionic design to reconstruct traditional parts for transport and aerospace applications are presented.