Powder Materials Processing and Fundamental Understanding: Control Macro and Microstructures I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee
Program Organizers: Elisa Torresani, San Diego State University; Kathy Lu, University of Alabama Birmingham; Eugene Olevsky, San Diego State University; Ma Qian, Royal Melbourne Institute of Technology; Diletta Giuntini, Eindhoven University of Technology; Paul Prichard, Kennametal Inc.; Wenwu Xu, San Diego State University
Wednesday 8:30 AM
March 22, 2023
Room: 25B
Location: SDCC
Session Chair: Elisa Torresani, San Diego State University; Alberto Molinari, University of Trento
8:30 AM
Additive Manufacturing and Spark Plasma Sintering: Fabrication of Powder Components with Cooling Channels: Elisa Torresani1; Maricruz Carrillo1; Eugene Olevsky1; Chris Haines2; Darold Martin3; 1San Diego State University; 2US Army DEVCOM - Army Research Laboratory; 3US Army DEVCOM – Armaments Center, Picatinny Arsenal
A novel method combining Additive Manufacturing (AM) technique of solvent jetting and Spark Plasma Sintering (SPS) of producing complex ceramic and metallic parts with designed internal channels is developed. This novel net shaping approach synergistically combines the capabilities of AM and SPS in producing complex components with internal channels. Along with geometric customization of the 3D printed mold, a major advantage of this method is the removal of the need for a long debinding process, usually necessary with other 3D printing methods, by using the SPS. High density ceramic and metallic complex parts with internal channels were successfully produced with close to theoretical densities. The conducted studies include the development of a model that can predict the evolution and/or distortions of the complex-shaped powder assembly during the sintering process. The model is based on the continuum theory of sintering formulations embedded in a finite element code.
8:50 AM
Cyclic Phase Transition Assisted Spark Plasma Sintering of AlCoCrFeNi Complex Concentrated Alloys: Runjian Jiang1; Elisa Torresani1; Eugene Olevsky1; Kenneth Vecchio2; 1San Diego State University; 2University of California San Diego
The accelerated densification and optimized microstructure can be achieved in the spark plasma sintering of dual-phase AlCoCrFeNi complex concentrated alloys at a low temperature by applying cyclic phase transition (CPT). The refined intragranular BCC/B2 structure and the networked dendritic FCC phase are formed in this CCAs after CPT process. The CPT-assisted sintering not only promotes a fully dense structure that is unobtainable in regular sintering at lower-limit temperature (800oC), but also promotes an accelerated densification that does not exist in regular sintering at upper-limit temperature (1000oC). This densification behavior is contributed by distinctive elemental redistribution and nano-grain cluster, which promote the mass transfer and the superplasticity behavior in this CCAs. The CPT-assisted sintering leads to the formation of strengthened BCC/B2 matrix and toughened FCC phase in AlCoCrFeNi CCAs, which can be a promising strategy bringing a synergistic effect to overcome the strength-ductility trade-off in CCAs.
9:10 AM
Freeze Casting of LaNbO4 Shape Memory Ceramics: Cesar Martinez-Cruz1; Olivia Graeve1; 1University of California San Diego
The shape memory effect allows a deformed material to recover an original shape upon the application of an external agent such as heat, with applications in the medical and aerospace industries, among others. Very few ceramics, including CeO2-ZrO2 and LaNbO4, in the form of micropillars or microspheres exhibit this effect. To expand the use of shape memory ceramics, researchers have scaled up sample size by producing porous structures. This approach reduces the number of surrounding grains on a particular volume of material, minimizing constraints during compression and preventing fracture. The freeze casting technique can create porous scaffolds made of thin ceramic lamellar walls, emulating single crystal structures, and optimizing the load distribution during compression. Therefore, in this study freeze casting was used to produce porous bulk scaffolds (3 mm samples) of LaNbO4 to achieve larger compression loads. Subsequently, the relevant tetragonal to monoclinic transformation was explored in the scaffolds.
9:30 AM
Effects of Inoculants on Melt Pool Geometry and Formation of Grain Structure in Inconel 718 Processed by Laser Powder Bed Fusion: I-Ting Ho1; Dhruv Tiparti1; Kai-Chun Chang2; An-Chou Yeh2; Sammy Tin3; 1Illinois Institute of Technology; 2National Tsing Hua University; 3The University of Arizona
This investigation rationalizes the influence of TaCr2 and TiB2 inoculant particle additions to Inconel 718 processed by laser powder bed fusion(L-PBF), with primary focuses on the melt pool physics and resulting microstructural evolution. Overall, addition of these inoculants reshaped the melt pool by decreasing the melt pool width and surface instability in terms of the balling phenomenon. Interestingly, the degree of melt pool penetration was found to vary with the addition of different inoculant particles. This change strongly imapcted the formation of grain structures as the angle of the melt pool interface varies and affects both the heat transfer and solidification rate. The cumulated effects accounted for a comparatively more columnar-grained structure with <101> texture formed in samples containing TaCr2 particles while a relatively equiaxed-grained structure with <001> texture formed in samples containing TiB2. The effectiveness of inoculants in L-PBF processed Alloy 718 will be discussed.
9:50 AM Invited
Anisotropy in Sintering of Parts Produced by BinderJet 3D Printing: Alberto Molinari1; 1University of Trento
Dimensional shrinkage during sintering of metallic green parts produced by Binderjet 3D printing is anisotropic. Shrinkage is larger along the building direction than in the building plane and even in this plane, it is slightly different along the directions parallel to the printer head and the roller displacement. The evolution of shrinkage anisotropy during the sintering cycle was investigated by dilatometry and correlated to the microstructural features of the green parts. In particular, the packing of the particles and the evolution of the neck size was characterized by the metallographic analysis and by the measure of thermal conductivity along the three directions.The influence of gravity was also investigated, by changing the orientation of the parts during the sintering step.
10:20 AM Break
10:40 AM Invited
Tuning Nano/microstructure and Properties by Densification of Metastable Powders: Gottlieb Uahengo1; Darren Dewitt1; Yasuhiro Kodera1; Javier Garay1; 1University of California San Diego
The ability to control phase content can be powerful for tuning material properties. We present strategies for phase content design by leveraging metastability of powders and resulting ceramics. Magnesium aluminate spinel (MgAl2O4) and yttria stabilized zirconia (YSZ) are important structural ceramics with proven applications as a hard, temperature resistant materials and high strength optical windows. In the spinel case, we present a study of the reaction densification of nano-sized MgO (nMgO) and metastable γ-Al2O3 to form MgAl2O4 instead of the typical stable α-Al2O3 and micrometer-sized MgO (μMgO). We show that the reaction kinetics of γ-Al2O3 – nMgO are substantially faster and occur at significantly lower temperatures compared to previous kinetic studies of α-Al2O3 – μMgO, revealing that they are not controlled by the same mechanism. In the YSZ case, we show that the phase content can be varied in fully dense transparent ceramics to optimize optical and mechanical properties.
11:10 AM Invited
Young Leaders International Scholar – JIM: Intermetallic Compounds as Catalysts and Usefulness of Metallurgy: Takayuki Kojima1; 1Shinshu University
Novel catalytic properties are often exhibited in intermetallic compounds due to surface ordered structures and unique electronic structures. Catalysis is usually investigated using nanoparticles precipitated on oxide supports, which are prepared by liquid chemical processes. However, much effort is needed to optimize synthesis conditions for supported intermetallic nanoparticles, and of which reproducibility is not good. Thus, it is difficult to conduct a proper screening of intermetallic catalysts and a fundamental research comparing catalysis among different intermetallics. These problems can be solved by metallurgical synthesis. Many intermetallics can easily be synthesized by metallurgical methods including arc-melting with high reproducibility. Since intermetallics are usually brittle, powder catalysts can be obtained by crushing using a pestle and mortar. Such a powder is suitable for screening and fundamental research. Moreover, it is valuable if supported intermetallic nanoparticles can be synthesized by ball-milling, which must be reproducible and needs less effort to optimize synthesis conditions.
11:40 AM
Effect of Powder Morphology on Densification and Microstructural Gradients of Titanium in Spark Plasma Sintering: Alexander Preston1; Kaka Ma1; 1Colorado State University
This study addresses the key role that powder morphology plays in the densification behavior and microstructural gradients that occur in spark plasma sintering. First, a strategy to incorporate mater sintering curves (MSC) into a thermal-electric (TE) finite element modeling (FEM) will be discussed to achieve continuous nodal-specific simulation of the evolution of thermal and electrical properties of the powder compact with respect to both relative density and temperature during sintering. Lab-scale Ti samples (diameter ~ 20 mm) were fabricated for construction and validation of MSC, whereas scaled-up Ti samples (diameter 65~70 mm) were made and characterized to verify the accuracy of the MSC - TE FEM combined model. The verified MSC - TE FEM combined model is then applied to investigate the effect of powder morphology. Key findings reveal that powders having a larger activation energy of sintering exhibit a greater gradient in microstructure.
12:00 PM
AddFAST: A Hybrid Technique for Tailoring Microstructures in Titanium-Titanium Composites: Cameron Barrie1; Beatriz Fernandez-Silva1; Rob Snell1; Iain Todd1; Martin Jackson1; 1The University of Sheffield
The advantages of FAST sintering have prompted much process research and application. From this came opportunities to investigate the potential for designing complex interpenetrating microstructures by combining the powder bed with a pre-built solid structure, which bonds with the powder to become one. Producing the structure through Additive Manufacturing yields a columnar grain morphology and texture, contrasting to the powder grains when bonded and creating a controllable composite microstructure of interpenetrating grain types. Here, we demonstrate with Ti-6-4 that this AddFAST technique successfully creates parts with this complex microstructure. The samples show a precise arrangement of grain sizes and texture with high densification and bonding. This demonstrates the technique’s viability and the process parameter values to control the final microstructure, with the combination of grain morphology and texture leading to potential novel mechanical and functional behaviours. Verifying this AddFAST process creates opportunities to design controlled, complex microstructures in small parts.