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•NiTiC alloy wires were prepared by accurately adjusting the C content.•NiTi alloy with 0.03 wt% C exhibits excellent tensile strength and tensile fatigue life.•Stacking faults in ...different directions in eutectic TiC form Lomer-Cottrell locks.•Stacking faults occur in grain boundaries of eutectic TiC in contact with matrix.•Eutectic TiC hinders the movement of adjacent grain boundaries and dislocations.
According to the phase diagram, 0.03 wt% (C0.03) and 0.05 wt% (C0.05) carbon were added to Ni50.2Ti49.8 alloy, and the alloy wires with a diameter of 1.2 mm were prepared by vacuum induction melting and drawing. The results show that during melting and solidification, C combines with Ti in C0.03 and C0.05 to form eutectic TiC and primary TiC, respectively. Compared with the NiTi alloy wire without C, the tensile fatigue life (22866 cycles under 700 MPa tensile stress) and tensile strength (1536 MPa) of the alloy were increased by 39 % and 22 % respectively when 0.03 wt% C was added. With the further increase of C content to 0.05 wt%, the two properties began to deteriorate. This is mainly related to the changes of matrix phase composition, second phase morphology and internal microstructure caused by the addition of different amounts of C. The research results show that on the premise of following the requirements for C content (C ≤ 0.04 wt%) in the international standard ASTM F2063-18 for medical NiTi alloy composition, adding a certain amount of C (such as 0.03 wt%) to NiTi alloy is beneficial to improving the tensile strength and tensile fatigue life of wire.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The trade-off between the safety and effectiveness of NiTi wire in practical applications has consistently hindered its advancement. This underscores the significance of adjusting its microstructure ...via appropriate heat-treatment techniques. This study systematically investigates the evolution of the constitution phases of the matrix and the grain size as the aging time increases from 3 min to 3 h at 550 °C for Ni50.9Ti49.1 wire, and highlights the significant role of the R phase in static/cyclic tensile failure behavior. When aged for 30 min, the matrix consists mainly of the B2 phase, similar to the as-received wire, while it tends to transform into the R phase during loading (intermediate-R phase). In contrast, aging for 3 h leads to the formation of the R phase as the matrix phase (matrix-R phase). The two types of R phase are discussed and compared in detail with regard to their contribution to the static/cyclic tensile failure behaviour. The longest fatigue life was obtained in wires with the R phase as the matrix phase, which was due to the combined effect: (i) the rapid attainment of a stable state so as to minimise the extent of phase transformation; (ii) coordination deformation of twin and dislocation to alleviate stress concentration; (iii) and the strong bonding between Ti2Ni and the matrix that reduces the occurrence of the “stretching into the hole-coalescence-microcrack process”. The enhanced flexibility observed in the wire with matrix-R phase is due to its reduced elastic modulus and lower transformation plateau. The increase in plasticity is linked to changes in the wire's fracture behavior resulting from grain growth. Such microstructural changes allow the alloy wire to exhibit a more uniform plastic deformation under stress, which in turn postpones the onset of significant fracturing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study explores the impact of micron-Ti microalloying and laser remelting on the microstructure and mechanical properties of laser powder bed fusion (LPBF) Al–12Si alloy, analyzing the underlying ...reasons. The findings show that the tensile strength and elongation at 300 °C (184 ± 13 MPa and 7.4 ± 1.4 %) are on par with other LPBF heat-resistant Al alloys, such as near-eutectic Al–Ce and Al–Ni. Introducing micron Ti (1 wt%) to AlSi12 effectively eliminates the α-Al texture and refines the grain structure, thanks to the strong nucleation effect from the formed D022-(Al, Si)3Ti, leading to enhanced tensile strength in both as-built and heat-treated (300 °C for 2 h) samples, while maintaining ductility within the typical range for LPBF near-eutectic Al–Si alloys. Laser remelting further decreases the presence of unmelted Ti powder in AlSi12Ti and encourages the formation of D022-(Al, Si)3Ti, offering insights into LPBF Al alloy composition design through promoting the melt of the modified powder and improving material homogeneity, especially for incorporating micron powders with high melting points. Additionally, the superior mid-high temperature properties (300 °C) of AlSi12+1 wt% micron-Ti contribute to expanding the database of LPBF Al alloys.
•AlSi12 and AlSi12 + 1 wt% micron-Ti alloys were prepared by LPBF.•Ti microalloying refines the grain size and eliminates α-Al texture of AlSi12.•The laser remelting strategy facilitates the dissolution of unmelted Ti powder.•The tensile strength at 300 °C of AlSi12 was improved through 1 wt% Ti microalloying.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•1 Ni50.2Ti49.8 and Ni50.9Ti49.1 deformation mechanisms determine tensile fatigue life.•2 Twins, SFs, and dislocations in Ni50.2Ti49.8 are coordinated to extend fatigue life.•3 Twins ...extending across adjacent grains can strengthen grain boundaries.•4 Twins increase dislocation movement space by changing dislocation movement direction.•5 Planar dislocation microstructures limit dislocation movement during cyclic tensile.
This study prepared near-equiatomic NiTi wires with excellent cyclic tensile fatigue life and proposed the mechanism by which deformation microstructure impacts fatigue life. The fatigue life of Ni50.2Ti49.8 was discovered to be 1.8–2.1 times greater than Ni50.9Ti49.1 by the low cycle fatigue test with various test conditions (loading stress is 700 MPa/900 MPa, frequency is 5 Hz/2.5 Hz, and stress ratio is 0.1/0.2) at room temperature. Ni50.2Ti49.8′s matrix phase is R + B19′ with fewer slip systems. It tends to coordinate deformation with twinning, stacking faults, and wave dislocations during cyclic tensile. Cross-grain boundary twinning strengthens grain boundaries. Also, twinning can expand available space for dislocation movement, thereby reducing stress concentration and extending the fatigue life of Ni50.2Ti49.8. Ni50.9Ti49.1′s matrix phase is B2 + R and easy to form planar dislocation. This reduces the space for dislocation movement and causes premature fatigue fracture. Moreover, the second phase Ni4Ti3 in Ni50.2Ti49.8 is distributed uniformly throughout the matrix and exerts a strong pinning influence on the dislocation movement. This also facilitates the formation of multiple deformation microstructures in Ni50.2Ti49.8.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Graphite flake (GF)-reinforced Ti6Al4V (TC4) matrix composites were fabricated by spark plasma sintering, and electroless copper (Cu) plating on the surface of the GFs was introduced to slow the ...interface reaction between the GFs and the TC4 and to improve the interface bonding. The effects of sintering temperature and coating thicknesses on the microstructure and thermal conductivity (TC) of the composites were investigated. The results showed that the introduction of the Cu coating can significantly reduce the thickness of the titanium carbide (TiC) layer generated by the interface reaction between the GFs and the TC4, increase the density of TiC layer, and thus increase the TC of the composite. When the sintering temperature was below 1150°C, the TC gradually increased from 185.03 W m
−1
K
−1
before Cu plating to 232.4 W m
−1
K
−1
with the increase of the Cu coating thickness and sintering temperature. When the temperature was further increased to 1200°C, the TC deteriorated due to the increase in the thickness of the TiC layer. The high TC makes the GF/TC4 composites suitable candidates for heat transfer materials used in offshore engineering.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this study, pure titanium (Ti) and Ti-6Al-4 V (TC4) matrix composites reinforced with 50 vol% graphite flake (GF) were fabricated by spark plasma sintering (SPS) respectively. The effects of ...different matrix and sintering temperatures on the microstructure and thermal conductivity (λ) of the composites were systematically investigated. The results showed that the interfacial reaction between the GF and pure Ti or TC4 produced an intermediate layer of titanium carbide (TiC). The thickness of TiC layer in both composites increased with the sintering temperature. At the same sintering temperature, the thickness of interface reaction layer TiC in GF/TC4 composite was much lower than that in GF/Ti composite, which also made the λ of the former significantly higher than that of the latter. The best sintering temperature of the two composites was 1150 °C. Under this condition, the λ of 50 vol% GF/TC4 composite reached 185.03 W m−1 K−1, which is more than 25 times of the λ of the matrix. It is expected to solve the problem of low λ of Ti materials used in plate heat exchangers.
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•TiC phase was formed at the interface between reinforcement and matrix.•The thickness of TiC layer in both composites increased with sintering temperature.•GFs orientation tended to be parallel with increasing sintering temperature.•GF/TC4 composites showed higher λ than GF/Ti composites.•The λ of 50 vol% GF/TC4 composite was more than 25 times that of the matrix.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Ni50.2Ti49.8 wire with R-phase as the matrix was produced in the as-drawn state.•Cyclic phase transformation in Ni50.9Ti49.1 initiates microcracks in phase boundaries.•The absence of R-phase to B19′ ...transformation in Ni50.2Ti49.8 helps avoid microcracks.•The fatigue life of Ni50.2Ti49.8 is approximately 12 times that of Ni50.9Ti49.1.
Ni50.2Ti49.8 and Ni50.9Ti49.1 wires in cold-drawn state were compared regarding tensile fatigue life and fatigue fracture mechanism. Through process control, Ni50.2Ti49.8 with R-phase matrix at room temperature was achieved in as-drawn state without post heat treatment. The R-phase imparts exceptional fatigue performance to Ni50.2Ti49.8 wire with fatigue life approximately twelve times of that for Ni50.9Ti49.1 which comprises B2 phase and a small amount of B19′ under the same test conditions. The cyclic phase transformation under loading initiates microcracks in phase boundaries, leading to premature fracture of Ni50.9Ti49.1. In contrast, the R-phase presents exceptional stability against fatigue failure upon cyclic loading.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, a simple material preparation method is proposed to meet the requirements of efficient heat exchange interface materials for spacecraft on-orbit modular assembly. First, carbon ...nanotubes (CNTs) were uniformly dispersed on the surface of spherical copper (Cu) powder, and then the bulk was obtained by hot-pressing sintering. Finally, the Cu on the surface was removed by electrolysis, so that the CNTs can protrude from the surface to a certain height. After contacting with the matching materials, the exposed CNTs can fill the inevitable pores at the interface, increase the heat transfer channel, and effectively reduce the interface thermal contact resistance (TCR). By adjusting the type of CNT, contact pressure, the height of CNT protruding from the surface of Cu powder, the minimum TCR of the interface between the obtained Cu/oriented carbon nanotube (Cu/OCNT) composite and pure Cu was 25.4 mm2 K W−1 under 2.26 MPa, which is superior to most existing commercial thermal interface materials. Moreover, the heat exchange interface designed based on the prepared materials can be repeatedly contacted and separated, which is expected to provide a solution for the heat exchange of on-orbit modular assembly spacecraft.
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•A facile and effective preparation method to obtain composites with ultra-low TCR.•By constructing a vertical structure of CNTs can fill the pores at the interface.•The lowest TCR between the obtained Cu/OCNT composite and pure Cu was 25.4 mm2 K/W.•The heat exchange interface designed can be repeatedly contacted and separated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Psychiatric disorders such as anxiety and depression precipitated by substance use occurred during both use and withdrawal. Exosomes play significant roles in biological functions and regulate ...numerous physiological and pathological processes in various diseases, in particular substance use disorders (SUDs) and other psychiatric disorders. To better understand the role of exosomal miRNAs in the pathology of symptoms of anxiety and depression in patients with SUDs, we first isolated circulating exosomes from heroin-dependent patients (HDPs) and methamphetamine-dependent patients (MDPs) and identified exosomal miRNAs that were differentially expressed between patients and healthy controls (HCs). Furthermore, the correlations between exosomal DE-miRNAs and symptoms of anxiety and depression which were measured using Hamilton-Anxiety (HAM-A)/Hamilton-Depression (HAM-D) Rating Scales in the participants. Notably, the expression level of exosomal hsa-miR-16-5p, hsa-miR-129-5p, hsa-miR-363-3p, and hsa-miR-92a-3p showed significantly negative correlations with HAM-A scores in both HDPs and MDPs. But all of the 4 DE-miRNAs lost significant correlations with HAM-D scores in HDPs. Functional annotation analyses showed that the target genes of the DE-miRNAs were mainly enriched for "synapse", "cell adhesion", "focal adhesion" and "MHC class II protein complex". Our study suggests that a set of circulating exosomal miRNAs were associated with anxiety and depression in SUD patients and may have clinical utility as diagnostic and prognostic biomarkers.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Methamphetamine (MA) abuse results in neurotoxic outcomes, including increased anxiety and depression. Studies have reported an association between MA exposure and anxiety, nonetheless, the ...underlying mechanism remains elusive. In the present study, we developed a mouse model of anxiety-like behavior induced by MA administration. RNA-seq was then performed to profile the gene expression patterns of hippocampus (HIPP), and the differentially expressed genes (DEGs) were significantly enriched in signaling pathways related to psychiatric disorders and mitochondrial function. Based on these, mitochondria was hypothesized to be involved in MA-induced anxiety. Quercetin, as a mitochondrial protector, was used to investigate whether to be a potential treatment for MA-induced anxiety; accordingly, it alleviated anxiety-like behavior and improved mitochondrial impairment
. Further experiments
suggested that quercetin alleviated the dysfunction and morphological abnormalities of mitochondria induced by MA,
decreasing the levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and increasing the oxygen consumption rate (OCR) and ATP production. Moreover, the study examined the effect of quercetin on astrocytes activation and neuroinflammation, and the results indicated that it significantly attenuated the activation of astrocytes and reduced the levels of IL-1β, TNFα but not IL-6. In light of these findings, quantitative evidence is presented in the study supporting the view that MA can evoke anxiety-like behavior
the induction of mitochondrial dysfunction. Quercetin exerted antipsychotic activity through modulation of mitochondrial function and neuroinflammation, suggesting its potential for further therapeutic development in MA-induced anxiety.
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