Powder Metallurgy of Light, Reactive and Other Non-ferrous Metals: Powder Metallurgy of Non-ferrous and Refractory Metals
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee
Program Organizers: Ma Qian, Royal Melbourne Institute of Technology; James Paramore, Texas A&M University; David Yan, San Jose State University; Gang Chen, University of Science and Technology Beijing
Monday 2:00 PM
February 28, 2022
Room: 211B
Location: Anaheim Convention Center
Session Chair: James Paramore, United States Army Research Laboratory; David Yan, San Jose State University
2:00 PM
Investigations of Phase Transformations in a Blended Elemental Ti-Nb-Zr-O Alloys Prepared by a Field-assisted Sintering Technique: Dalibor Preisler1; Jiri Kozlik1; Josef Strasky1; Tomas Chraska2; Milos Janecek1; Hanus Seiner3; 1Charles University; 2Institute of Plasma Physics, Czech Academy of Sciences; 3Institute of Thermomechanics, Czech Academy of Sciences
Several Ti-Nb-Zr-O alloys were prepared as gradient samples from elemental powders, followed by compaction by field-assisted sintering technique (FAST). The gradient was created in Nb content for each sintered sample. The chemical and phase composition of the solution treated conditions was investigated using scanning electron microscopy and X-ray diffraction. Elastic moduli were determined by resonance ultrasound spectroscopy of individual layers and mechanical behavior was studied by microhardness and compression testing. α" martensite is formed when Nb concentration is below 20 wt%. Between 23 and 29 wt% Nb, ω phase is formed during quench and pure β is retained above 29 wt% of Nb. Elastic modulus is strongly influenced by the phase composition, ranging from 65 GPa (β) to 100 GPa (β+ω). When O content is 0.5 wt%, several layers undergo a martensitic transformation β->α" during deformation, usually marking the presence of special effects, such as transformation induced plasticity or superelasticity.
2:20 PM
Microstructural/Mechanical Properties Relationship of Elongated Ti-15Mo Bars Produced by Unconventional Spark Plasma Sintering Technology: Mariano Casas-Luna1; Adrián Majoros1; Anna Veverková1; Dalibor Preisler1; Josef Stráský1; 1Charles University
Titanium and its alloys are widely used due to their excellent mechanical properties and corrosion resistance, being suitable materials for aircraft and medicine industries. Spark plasma sintering (SPS) is one of the powder metallurgy technologies that has gained attention in research and industry because it offers fast processing and control of the final microstructure, transforming powders into sintered specimens using a mold, generally limited to simple shapes and small dimensions. In this study, an unconventional SPS arrangement was implemented to sinter a metastable beta-Ti15Mo alloy to produce elongated bars of 10 mm in diameter and nearly 100 mm length, overcoming the size limitations in SPS processing. Obtained Ti15Mo bars were processed to study the microstructural-mechanical relationship at different conditions, i.e., SPS-sintered, SPS-sintered + forged, and conventionally prepared alloy. Compact and homogeneous bars with an average grain size of 200 μm were achieved and compared in terms of their mechanical properties.
2:40 PM Invited
Titanium Near Net Shape PM Parts Produced by Direct Powder Forging: Bernard Tougas1; Sébastien Germain-Careau1; Elena Kolitsky1; Gheorghe Marin1; 1Quebec Metallurgy Center
Additive manufacturing of titanium parts is a market that has been growing significantly for the past decade. The intricate geometry that the technique offers pushes the growth of the process. However, reclaiming the unused powders from the powder bed is limited because offcuts are generated by the laser that sinters and agglomerates powders near the printed parts. Another source of offcut powders is atomization where the bigger powders are discarded. Recycling these powders and agglomerates has always been an industry challenge, but a recently published work has proven that titanium direct powder forging (DPF) could be used to produce high-quality biomedical grade blanks from these offcuts. The current study looked at the DPF process to produce near net shape parts by including a close die forging step. Results show that high-quality parts can be produced and that the microstructure and the mechanical properties satisfy the biomedical standards.
3:05 PM
Influence of Calcium Powder in Heavily Deformed Aluminum-calcium Metal-metal Composites: Dustin Hickman1; Trevor Riedemann2; Jordan Tiarks2; Iver Anderson2; 1Iowa State University; 2Ames Laboratory
Although most overhead power transmission cables are constrained to strengthening through addition of less electrically conductive core strands, a monotype composite conductor design throughout the cable cross section is made possible by Al/Ca heavily deformed metal-metal composite (DMMCs) wires. Utilizing a powder metallurgy (PM) route, Al/Ca DMMCs provide competitive strength and conductivity to “strong-core” overhead conductors for reduced losses, especially in high-voltage direct current (HVDC) applications. In the development of Al/Ca DMMCs, Hall-Petch strengthening with electrical conductivity relating directly to the rule-of-mixtures was observed. With this tradeoff for increased strength and decreased conductivity, the tunability of this PM approach allows facile optimization of these properties. Also, the opportunity exists to decrease Ca powder size to exploit enhanced Hall-Petch strengthening, while decreasing vol.% Ca loading to increase conductivity. This research focuses on such optimization of Al/Ca DMMC conductor design. Funding from DOE-OE through DE-AC02-07CH11358.
3:25 PM Break
3:40 PM Keynote
Microstructural Refinement and Uniformity of Refractory Metals: Lin Zhang1; Xingyu Li1; Xuanhui Qu1; 1University of Science and Technology Beijing
Refractory metals such as tungsten (W) and molybdenum (Mo) are useful in many technologies, including fusion energy, aerospace, microelectronics and other applications under extreme environments. Processing such a refractory metal at high-temperature conditions (sintering, thermomechanical processing and heat treatments), unavoidably results in heterogeneous behaviors in sintering, grain growth, plastically response and recrystallization, makes it difficult to produce microstructural refinement and uniformity. Meanwhile, the contaminated impurity often leads to terrible uncertainty of microstructural evolution when considering material design. Therefore, this work starts by presenting polycrystalline W with different purity, aiming to understand the microstructural and mechanical evolution during sintering, hot-rolling and recrystallization, and the possible effect of contaminated impurities on them. Further, it provides a simple pressureless sintering method to fabricate dense bulk W and other refractory metals with uniform microstructure and ~200 nm grain size.
4:20 PM
Scaling Up Porous Copper Foams by Planetary Milling and Oxide Reduction: Julian Tse Lop Kun1; Adam Rutherford1; Mark Atwater1; 1Liberty University
Powder metallurgy (PM) offers a growing list of benefits for the diversity of alloys possible and the ability to create complex geometries. The challenge is that powder processing methods based on templates are often complex, and simple methods, such as loose powder sintering, result in low pore volume fractions. The oxide reduction method allows individual particles to be foamed in loose form or processed by traditional PM and foamed at a later stage. The additional porosity can help bridge the gap between simplicity and performance. This method has only been demonstrated in small quantity, high-energy ball milling. In this report, we apply planetary ball milling to realize an order of magnitude increase in output with the potential for even more. The advancements in producing porosity within particles by oxide reduction, the combination with traditional porous powder methods, and the future implications for these unique materials will be discussed.
4:40 PM
Accelerated Powder Consolidation in Nanocrystalline Materials Competes with Organic Burn-off: Yannick Naunheim1; Christopher A. Schuh1; 1Massachusetts Institute of Technology
The thermal debinding of organic additives typically occurs at the lower end of the temperature cycle as compared with the consolidation of powder in many additive manufacturing operations, due to the different process kinetics. In this talk, we examine cases of powder consolidation where the volatilization of the processing aids is kinetically challenged by the low-temperature onset of densification. The systems are based on Ni and are nanocrystalline, and therefore exhibit accelerated diffusional kinetics. We also consider cases that include a phase separation step that is intentionally designed to accelerate sintering. In such systems, the onset temperature for densification is so aggressively lowered that it competes kinetically with the organic debinding, which can lead to porosity by trapped fugitive species, creating new challenges to the acceleration of sintering.