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Ti-6554 (Ti-6Cr-5Mo-5V-4Al) alloy has attractive potential as a new structural material in the aviation field due to its excellent mechanical properties. However, it is expensive to manufacture, which can limit its application. Powder metallurgy (PM) is an economic technology to reduce the cost of titanium alloys. In this study, PM Ti-6554 alloy was prepared using irregular powder via vacuum sintering followed by forging. The influence of cooling rate (air cooling and water quenching) of as-forged sample on its microstructure was studied by scanning electron microscopy, electron backscatter diffraction and other analytical means. Experimental results showed that different cooling rates determined the structures of α and β phases. Compared with air-cooled sample, the water-quenched sample only had β phase microstructure without α phase precipitates. As-forged PM Ti-6554 alloy subjected to water quenching achieved ultimate tensile strength of 942 MPa and elongation of 20% and also had fine β grains of 10 μm. After solution treatment and aging, the sample exhibited high ultimate tensile strength (1211 MPa) and elongation (13.8%). Overall, PM Ti-6554 alloy possessed a good combination of high strength and reasonable ductility. This work marks a vital step forward in the application of high-performance PM Ti-6554 alloys. [ABSTRACT FROM AUTHOR]

Lithium-rich material (SOP) with special nano-micron composite structure is synthesized by simple one-step oxalic acid method. The SOP sample is made of micron particles (1–3 μm) and nano-particles (~ 100 nm). Compared with the co-precipitation prepared lithium-rich materials (COP), SOP has good rate performance and cycle stability. The specific discharge capacity of SOP sample reaches 104.2 mAh/g at 10 C, while that of COP sample is only 68.5 mAh/g. After 300 cycles, SOP still has a specific discharge capacity of 201 mAh/g and the capacity retention rate is 89.6%, while COP only has a specific discharge capacity of 135.8 mAh/g and the capacity retention rate is 58%. Structure allocation with nano-micron particles is conducive to electrochemical performance improvement. This study provides a new idea for the synthesis of lithium-rich material with better performance. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) offers cost-effective potential for manufacturing titanium and titanium alloys. High oxygen content on titanium powder surface is a key problem affecting the mechanical properties of PM Ti alloys. Therefore, this study proposes a chloro-deoxidation method to reduce the oxygen content of titanium powder via introducing stannous chloride (SnCl2) into titanium powder. In the sintering process, SnCl2 reacts with the surface oxide on titanium powder to remove the oxide film, and thus forms gas TiClxOy escaping from Ti matrix, resulting in the decrease of oxygen content. With ~ 2.5 wt.% SnCl2 addition, the oxygen content reduces from 0.6 wt.% to 0.5 wt.%. Accordingly, the elongation of as-sintered Ti-SnCl2 sample significantly increases from 4.8% to 11% (increasing by 129%), while the tensile strength decreases from 815 MPa to 788 MPa. After HIP treatment, the elongation increases from 11% to 13%, and the strength is about 765 MPa. Although same Sn content (5 wt.%) is added in Ti samples, Ti-SnCl2 sample shows higher elongation value of 9.4% compared to Ti-Sn sample (3.6%), due to lower oxygen content. [ABSTRACT FROM AUTHOR]

The effects of solution-aging treatment on microstructure and mechanical properties of powder metallurgy (PM) Ti-6554 titanium alloy were investigated. PM Ti-6554 titanium alloy can achieve a good balance between strength and ductility after solution treatment at 810°C/30 min with furnace cooling and aging treatment at 520°C/6 h. Accordingly, the ultimate tensile strength, yield strength and elongation were 1360 MPa, 1323 MPa and 9.0%, respectively. The alloy had smaller α phase grain size (~ 0.69 μm), and its volume fraction was 73%. When the solution temperature increased from 810°C to 850°C, the ultimate tensile strength increased to 1601 MPa, the yield strength increased to 1543 MPa, and the elongation reduced to 3.5%. Microstructure results showed that the grain size of α phase gradually increased, while the volume fraction of α phase showed the opposite trend. When the solution temperature remained constant, slower cooling rate was beneficial to increase the alloy strength and maintain the strength-plasticity matching. [ABSTRACT FROM AUTHOR]

This study provides an effective surface modification method for Li-rich layered oxide (LLO, Li1.2Mn0.54Ni0.13Co0.13O2) with Al2O3 coating. Strong organic acid TFBDC (2,3,5,6-tetrafluoro-1,4-phthalic acid) accumulates near alkali metal oxide LLO to form uniform Al-TFBDC coating. Al-TFBDC modified LLO is subjected to heat treatment to form Al2O3 coating on the surface of LLO. This uniform coating protects LLO from direct contact with electrolyte and does not block the migration of Li+. Meanwhile, F− is successfully doped into LLO particles. The LLO coated with doping has clear layer structures, and its electrochemical properties have been significantly improved. The rate performance is increased by 66% at 10 C. After 150 cycles, its capacity retention rate is 92.5%, while that of uncoated LLO is only 55.8%. [ABSTRACT FROM AUTHOR]

Fe-3.3Si-6.5Cr powders were first treated by phosphoric acid solution and then mixed with epoxy-modified silicone resin uniformly, forming insulation coating. The Fe-3.3Si-6.5Cr soft magnetic composites were prepared by compaction and annealing treatment of the coated Fe-3.3Si-6.5Cr powders. The microstructure and composition of Fe-3.3Si-6.5Cr powders were analyzed by scanning electron microscope coupled with energy-dispersive spectrometer, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy, respectively. The magnetic properties were determined by the LCR bridge tester and an auto testing system for magnetic materials (MATS-2010SA). Results show that both proper phosphating treatment and annealing at higher temperature can improve the permeability and reduce the core loss of the Fe-3.3Si-6.5Cr SMCs. When the concentration of phosphoric acid was 0.5 wt% and the heat treatment temperature reached 500 °C, the Fe-3.3Si-6.5Cr SMCs showed the optimized magnetic properties, including the permeability (μe) of 44.7 H/cm, the core loss (P) of 521.8 mW/cm3 at the saturated magnetic flux density of 50 mT, and the frequency of 100 kHz. The Fe-3.3Si-6.5Cr SMCs with distinguished magnetic properties provide great application prospect in various fields such as filter inductors, transformers, and sensors. [ABSTRACT FROM AUTHOR]

A novel and quick process combining self-propagating reaction with vacuum-expendable pattern casting is presented to accomplish integrated preparation of millimeter-thick TiCp/Al composite coatings on the Al substrate. Titanium and graphite powders were mixed with the polytetrafluoroethylene (PTFE) additive and pasted on the expendable polystyrene (EPS) followed by compaction. Al components with in situ TiCp/Al composite coating were simultaneously synthesized at a relatively low temperature of molten Al, which was poured into the assembly of EPS and powder compact inside the silica sands. Differential scanning calorimetry, x-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy and transmission electron microscopy were used to systematically investigate the thermodynamic characteristics of the reaction, the phase constituents, microstructure and tribological properties of the coatings. The infiltration model describing the densification of the reaction coatings was also developed for the critical wetting condition. The wear characteristics were assessed using a pin-on-disk tribometer with various loads. Results showed that uniform TiC particles stimulated by the PTFE-activated self-propagating reaction afforded superior mechanical properties and wear resistance. [ABSTRACT FROM AUTHOR]

With higher power, frequency and longer life of microwave tubes, cathode heater assembly is being modified to enhance the warm-up performance and reliability, which are governed by ceramics thermal conductivity, electrical resistivity and shrinkage. In present work, a potting material with a high thermal conductivity of 22.14 W/(m K) and low linear shrinkage of 5.5% was prepared using two kinds of alumina powders with different size and morphology. Aqueous slurries were produced for centrifugal casting. The highest solid loading slurries with 70 vol.% were obtained. Green body with relative density above 70% was easily made from slurries using centrifugal casting. Relative sintered density reached 86.75% maximum without any sintering aids. Rheological behavior of slurries, potting microstructure, sintering shrinkage and thermal conductivity were analyzed. Continuous particle distribution, series and parallel models were used to guide the powders proportion and explain the thermal conductivity. The potting material thermal conductivity experimental data agreed with the series and parallel models when the weight parameter ξ was between 0.3 and 0.5. [ABSTRACT FROM AUTHOR]

Microstructure evolution and variations in mechanical properties of Al-Al2O3 nanocomposite produced by powder metallurgy were investigated and compared with commercially pure aluminum (Al-1050) after furnace annealing. Fine gas-atomized Al powder compacts were first sintered in flowing nitrogen, subsequently consolidated into wires by rotary swaging and eventually annealed at 300 and 500 °C for 24 h each. Scanning and transmission electron microscopy with energy-dispersive spectroscopy was utilized to document the microstructure evolution. Rotary swaging was proven to lead to a marked decrease in grain size. After heavy swaging to true deformation degree of φ = 6 and annealing at 500 °C, obvious recrystallization was observed at Al-1050’s existing grain boundaries and the crystals began to grow perpendicular to the flow direction. In the Al-Al2O3 nanocomposite, fabricated from d50 = 6 μm Al powder, recrystallization partially occurred, while grains were still extremely fine. Due to the dual role of fine-grained Al2O3 dispersion strengthening, the nanocomposite showed improved mechanical performance in terms of tensile strength, approximately twice higher than Al-1050 after annealing at 500 °C. [ABSTRACT FROM AUTHOR]

This study provides an effective surface modification method for Li-rich layered oxide (LLO, Li1.2Mn0.54Ni0.13Co0.13O2) with Al2O3 coating. Strong organic acid TFBDC (2,3,5,6-tetrafluoro-1,4-phthalic acid) accumulates near alkali metal oxide LLO to form uniform Al-TFBDC coating. Al-TFBDC modified LLO is subjected to heat treatment to form Al2O3 coating on the surface of LLO. This uniform coating protects LLO from direct contact with electrolyte and does not block the migration of Li+. Meanwhile, F− is successfully doped into LLO particles. The LLO coated with doping has clear layer structures, and its electrochemical properties have been significantly improved. The rate performance is increased by 66% at 10 C. After 150 cycles, its capacity retention rate is 92.5%, while that of uncoated LLO is only 55.8%. [ABSTRACT FROM AUTHOR]