HEA 2023: Powders and Additive Manufacturing II
Program Organizers: Andrew Detor, DARPA/DSO; Amy Clarke, Los Alamos National Laboratory
Wednesday 1:40 PM
November 15, 2023
Room: William Penn Ballroom
Location: Omni William Penn
Session Chair: Matthew Dunstan, US Army Research Laboratory
1:40 PM Introductory Comments
1:45 PM
Direct Ink Writing Printing and Microstructural Engineering of Lightweight Al10Co25Cr8Fe15Ni36Ti6 Micro-lattices: Ming Chen1; Dingchang Zhang1; Ya-Chu Hsu1; David Dunand1; 1Northwestern University
Given its superior high-temperature strength and oxidation resistance, Al10Co25Cr8Fe15Ni36Ti6 is a promising alloy for high-temperature structural applications. Additive manufacturing provides high flexibility for fabrication of complex shapes, but, for Al10Co25Cr8Fe15Ni36Ti6, traditional AM approaches based on laser beam fusion/solidification induce cracking and warping due to high temperatures and thermal gradients. Here, we demonstrate 3D direct ink writing technique can fabricate lightweight Al10Co25Cr8Fe15Ni36Ti6 micro-lattices, enabling complex geometries with superior strength and ductility for applications in high-temperature structural components. Elemental powders are suspended, together with binder, into an ink which is 3D-extruded into thin struts, in air at ambient temperature. Printed green bodies are sintered at elevated temperatures to decompose binder and densify powders. We discuss various approaches to achieve high quality micro-lattices and mitigate oxidation and impurities issues during sintering; we also describe effects of compositions on morphologies and volume fraction of γ’ precipitates to achieve high strength at elevated temperatures.
2:05 PM
Exploring Thermomechanical Post-processing Techniques to Improve the Mechanical Strength of an SLMed CoCrFeMnNi: Joseph Agyapong1; Alexander Czekanski1; Solomon Boakye-Yiadom1; 1York University
Abstract:This study investigates thermomechanical post-processing techniques, including deep cryogenic treatment and annealing heat treatment, to enhance the mechanical strength of a selective laser melted (SLMed) CoCrFeMnNi high-entropy alloy. The alloy exhibits high strength, corrosion resistance, and ductility, making it suitable for aerospace, automotive, and biomedical applications. The research utilizes SEM and TEM microscopy techniques for microstructural analysis. Fracture toughness is evaluated using SENB, while high strain rate impact and hardness tests assess dynamic behavior. The results provide insights into the effects of thermomechanical processing on the alloy's mechanical properties, contributing to the optimization of high-entropy alloys produced via selective laser melting. This study advances additive manufacturing knowledge and facilitates the development of robust metallic components for diverse industries.
2:25 PM
3D Ink Extrusion Printing of CoCrFeNi and (Zr0.50Ti0.35Nb0.15)80Al20 Microlattices: Ya-Chu Hsu1; Dingchang Zhang1; Ming Chen1; David Dunand1; 1Northwestern University
The preparation of high-entropy alloys (HEAs) via 3D ink-extrusion printing has been increasingly used in the past few years. Green bodies with complex shapes can be printed layer by layer by using powder-loaded liquid ink at room temperature. This method offers flexibility in using elemental, oxide, or hydride powders and avoids the problems of residual stress and textured microstructure. In this work, microlattices with open channels are 3D ink-extrusion printed from inks containing a powder blend of oxides and graphite powders. Metallic CoCrFeNi alloy microlattices are then achieved by co-reduction in different atmospheres and sintering. Compression properties of sintered CoCrFeNi microlattices are measured at room temperature. Microlattices of the (Zr0.50Ti0.35Nb0.15)80Al20 alloy are created via 3D extrusion of inks containing ZrH2, Ti, Nb, and TiAl3 powders. Further hydride decomposition, elemental interdiffusion, homogenization, and densification of the struts of the microlattices were studied. Their compressive properties are measured at elevated temperatures.
2:45 PM
The “Commodity Approach”: A Novel and Sustainable Method to Develop Non-equitomic CoCrFeNiMox High Entropy Alloys: Jose Torralba1; S. Venkatesh Kumaran1; Dariusz Garbiec2; Alberto Meza3; 1Universidad Carlos III Madrid-Imdea Materials Institute; 2Łukasiewicz Research Network – Poznań Institute of Technology; 3IMDEA Materials Institute
One obstacle to developing HEAs is the need to use many alloying elements, which are considered critical and strategic and expensive metals. However, it has been demonstrated[1,2] that HEAs can be obtained from combinations of commodity alloys (e.g., nickel and cobalt-based superalloys or stainless steels). This possibility opens up the prospects for the development of HEAs using raw materials that can come from the recycling of commodity alloys, which are available sources of metals such as Ni, Fe, Co, Cr, or Mo, which, being available in the form of scrap, lose their critical character and offer a cheaper possibility than the direct use of pure metals. In this work, non-equiatomic high entropy CoCrFeNiMox alloys are developed from three PM routes: SPS, LBPF (additive manufacturing), and MIM. [1] J.M. Torralba, S. Venkatesh Kumarán, Mater. Lett. 301 (2021). [2] S. Venkatesh Kumaran, et al., Mater. Sci. Eng. A 878 (2023) 145207.
3:05 PM Cancelled
Development of a Process Optimization Framework for Fabricating Fully Dense NiCoCr Medium Entropy Alloy Using Laser Directed Energy Deposition: Thaer Syam1; Bilal Mansoor2; Ibrahim Karaman1; 1Texas A&M University; 2Texas A&M University at Qatar
Multi-principal alloys, such as medium entropy alloys (MEAs) show promise due to their superior mechanical properties such as high strength-to-weight ratios. Here, we report our initial results on laser-based Direct Energy Deposition (DED) of pre-alloyed NiCoCr - focusing on the challenges associated with achieving dense NiCoCr parts using this process. As a first step, basic single-track experiments were employed to chart the range of parameters including scanning speed, power and RPM, and a blend of geometric factors for hatch spacing and layer height was suggested to identify parameter combinations that accomplish desired build heights while minimizing the formation of porous regions. 19 parameter combinations were identified and prisms of 8mm by 8mm with variable target heights were printed for further analysis. Initial, printability maps were constructed based on the main process parameters, and criteria for hatch spacing, layer height and dilution limits as an output of the melt pool characteristics.