Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: Other Non-ferrous Materials
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Jurgen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology

Wednesday 8:00 AM
October 12, 2022
Room: 302
Location: David L. Lawrence Convention Center

Session Chair: Jonathan Putman, Exum Instruments; Ahmad Nourian, Northeastern University


8:00 AM  Cancelled
Copper Printing Capabilities via Binder Jet Printing: Sabina Kumar1; 1Eaton Corporation
    Binder Jet (BJ) Printing has proven to be compatible with a wide range of materials that would otherwise prove difficult to fabricate using any PBF system. Copper, for instance, owing to its high thermal conductivity, control over the melt cycles during fabrication via L-PBF poses a challenge. BJ allows for part fabrication at room temperature making it a more viable process for printing copper. With the target application being the electrical sector, the prime focus of this study will be on achieving properties such as high densification and improved electrical conductivity. One way of achieving higher green densities is by adopting ExOne’s patented Nanofuse(NF) binder. Alongside improved densities, the NF binder renders additional advantages such as better surface resolution and enhanced material properties. This talk will concentrate on the benefits of copper printing with BJ, at the as-sintered and HIP condition, as-well-as the improved properties with the NF binder.

8:20 AM  
Microstructure Evolution and Mechanical Properties of 3D Printed and Sintered Copper Parts: Kameswara Pavan Kuma Ajjarapu1; Luke Malone1; Carrie Barber2; Mark Barr2; Matteo Zanon2; Sundar Atre1; Kunal Kate1; 1University of Louisville; 2Kymera International
    In this work, a combination of Fused Filament Fabrication (FFF) and sintering were implement to fabricate high density copper parts via extrusion-based 3D printing technology. 58vol.% copper powder-filled polymeric feedstocks and filaments were prepared and characterized for physical, thermal, and rheological properties. Subsequently, the filaments were 3D printed into tensile and tablet geometries. An L9 Taguchi design of experiments was performed by varying print temperature, print speed, and layer height for three levels to identify optimal process conditions that can maximize green density and minimize surface roughness perpendicular and parallel to the build direction. Green parts were further sintered and characterized to understand the physical and mechanical properties of the final parts. Additionally, microstructure evolution with varying sintering conditions was studied to identify it’s influence on final part properties. This study provides a wholistic understanding of the structure-property-processing corelationship in 3D printed copper parts.

8:40 AM  
Post-process Heat Treatment Effects on Additive Manufactured Pure Copper: Wanxuan Teng1; Biao Cai1; Kenneth Nai2; Stuart Jackson2; Ian Campbell3; 1University of Birmingham; 2Renishaw PLC; 3Cookson Precious Metals Ltd
    Pure copper is highly desirable as a material for making heat exchangers, cooler and electrical components due to its good thermal and electrical properties. However, laser sintering of copper powder with an Infra-Red laser with a wavelength of 1070nm is a challenge because copper is highly reflective at that wavelength, only a few percent of the laser energy is absorbed into the powder to cause it to melt. The high thermal conductivity of copper and high laser energy required cause the melting process to be unstable and often results in poor electrical, thermal and mechanical properties of the finished parts. Post-print heat treatments were applied to optimize the thermal and electrical conductivity, achieving 374 W/mK and 99.5% IACS after 1000 °C/2 h annealing. The underlying mechanisms for the improvement of thermal and electrical conductivity were discussed based on microstructure characterization.

9:00 AM  
Simplifying Post-Processing of Copper Alloys Using: Owen Hildreth1; Sanaz Yazdanparast1; 1Colorado School of Mines
     Over the last few years, our group has developed novel methods to remove support structures, improve surface finish, and remove trapped powder from metal components fabricated using Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) technologies. This presentation details new new chemistries that bring self-terminating etching to copper alloys (copper, GRCop-42 and GRCop-84) to reducing processing costs and expand design freedoms. Impact of temperature and time were studied and surface roughnesses of Ra ≤ 2 µm are measured after support removal. This technology expands the capabilities of metals AM by simplifying post-processing. For example, the ability to remove internal supports and trapped powder enable metals Additive Manufacturing (AM) to fabricate complex propulsion systems with improved performance; components with complex internal passages (heat exchangers, propulsion systems); and thin walls structures. The ability to smoother exterior and interior surfaces is expected to improve mechanical performance and increase component lifetime.

9:20 AM  
Development of High Pressure Heat Treatment for L-PBF F357: Chad Beamer1; Pontus Nilsson1; Andrew Wessman2; Donald Godfrey3; 1Quintus Technologies LLC; 2University of Arizona ; 3SLM Solutions Americas
     Recent advancements in HIP equipment now offer the ability to integrate HIP and heat treatment in the HIP furnace with the aid of controllable high-speed cooling and in-HIP quenching and is referred to as High Pressure Heat Treatment. This approach has shown to not only offer improvement in productivity but provides a path to prevent anomalies during heat treatment including thermally induced porosity and part quench cracking or distortion. This presentation will cover the approach of HPHT. Then a study will be reviewed in detail capturing the use of HPHT on SLM Solutions printed alloy F357. Microstructure, tensile properties, and part distortion is evaluated. The results capture the development of a robust process method making it possible to prevent hydrogen blistering for a defect free AM material, strength properties exceeding that of MMPDS cast properties, and the ability to mitigate geometric distortion of complex part geometries.

9:40 AM  
Influence of Post-Processing Techniques on Process-induced Defects in AM AlSi10Mg and CP-Ti: Austin Ngo1; Hannah Sims1; John Lewandowski1; 1Case Western Reserve University
    Additive Manufacturing (AM) processes have versatile capabilities but are susceptible to the formation of non-equilibrium microstructures, process-induced defects, and porosity, which have deleterious effects on the mechanical performance of AM-processed structural materials. A variety of post processing techniques were investigated as a method of reducing process defect severity and improving mechanical properties. Specimens of Laser Hot Wire CP-Ti and LPBF AlSi10Mg were fabricated over a range of process parameters, followed by post processing in different ways to illustrate beneficial changes in mechanical performance. Fracture surfaces were analyzed using OM and SEM methods. The effects of post processing techniques on both LHW CP-Ti and LPBF AlSi10Mg will be discussed in terms of mechanical properties and fractography.

10:00 AM Break

10:20 AM  
Laser-powder Bed Fusion and Mechanical Properties of Al18Co30Cr10Ni32 Eutectic Multi-Principal Element Alloy: Thinh Hyunh1; Abhishek Mehta1; Nemanja Klejstan2; Asif Mahmud1; Kevin Graydon1; Marko Knezevic2; Brandon McWilliams3; Kyu Cho3; Yongho Sohn1; 1University of Central Florida; 2University of New Hampshire; 3DEVCOM US Army Research Laboratory
    A novel Al18Co30Cr10Fe10Ni32 eutectic multi-principal element alloy (MPEA) composition was gas atomized to produce powder feedstock, which was employed for laser powder bed fusion (LPBF) process optimization, followed by mechanical (tensile) testing and microstructural analysis. Melting was achieved in air at a superheating temperature of 1750 °C and atomized using Argon gas pressure of 2 MPa. LPBF optimization was performed as a function of laser power and scan speed, and density greater than 99.6 % was obtained using 350W and 1000 mm/s. The as-fabricated MPEA specimens consisted of FCC and BCC phases with cellular and lamellar eutectic microstructure. The as-built alloy had mechanical properties (tensile, yield and elongation of 1.4 GPa, 1.1 GPa and 21%, respectively) comparable to those of as-built IN718. Changes in microstructure and mechanical properties after high temperature exposure was examined by electron microscopy and x-ray diffraction, for analytical work to elucidate strengthening mechanisms.

10:40 AM  
Stainless Steel and Aluminum Alloy Development for Highly Consistent and Isotropic Properties in Laser Powder Bed Fusion: Benjamin Rafferty1; Jeremy Iten1; Aaron Stebner2; Akansh Singh3; Branden Kappes4; Sridhar Seetharaman5; Dyuti Sarker2; Soumya Mohan2; 1Elementum 3D; 2Georgia Tech; 3Colorado School of Mines; 4KMMD; 5Arizona State University
    To increase additive manufacturing (AM) robustness and reliability, there is a need for metal feedstocks that produce more isotropic and highly consistent properties. Current laser powder bed fusion (LPBF) feedstocks show variation in microstructure and mechanical properties based on build direction. By combining integrated computational materials engineering (ICME) with an inoculant-based approach, we experimentally validated a more isotropic 300 series stainless steel and an extraordinarily consistent high-strength 5000 series aluminum metal matrix composite. The 300 series stainless steel showed UTS measurements consistency across X-Y and Z direction of 96% compared to 90% for 316L. The 5000 series aluminum MMC showed >99% equivalent UTS across X-Y and Z directions and showed no change in YS or UTS from the as-built condition after a 2-hour stress relief at 300 C. The 5000 series aluminum MMC demonstrated a yield strength 3 times that of wrought 5083-O with 7% elongation.

11:00 AM  
Additively Graded Materials for Thermal Management: Gianna Valentino1; Sharon Park2; Alex Lark1; Mo-Rigen He2; Kevin Hemker2; 1Johns Hopkins Applied Physics Laboratory; 2Johns Hopkins University
    Extreme environment applications require high temperature structural materials, such as refractory metals, but their high density, manufacturing difficulties, and limited high temperature characterization inhibit their widespread use. Advances in additive manufacturing (AM) promise to be a game-changer in the fabrication and implementation of refractory-based components via near-net-shape processing. However, the characterization of refractory high temperature properties is rare, much less for those made via AM. Here we report on the development and optimization of AM processing parameters for tungsten and tantalum refractory alloys to obtain a deeper fundamental understanding of the AM structure-property relationships. Emphasis will be placed on characterizing the microstructure and high temperature mechanical performance, ultimately aimed at improving thermal modeling of AM refractories for high temperature applications. Although still in its infancy, a study to fabricate refractory graded materials is ongoing and the results will be discussed for thermal management.