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A pre-formed martensitic quenching plus inverted multi-step austempering process is performed on a medium-carbon alloy steel: after austenitization, the specimen is cooled to 175 °C below the martensite start temperature (Ms), then raised to the first austempering step at 220 °C for 5 h, followed by the second step at 300 ℃ and held for 3 h. The conventional inverted multi-step austempering process and the one-step austempering process are carried out to form a contrast test. Through pre-formed martensitic quenching plus an inverted multi-step austempering process, the martensite/austenite (M/A) and bainitic ferrite in the microstructure are refined. The total time used for heat treatment is reduced markedly due to accelerating bainitic ferrite formation. This study provides theoretical support for the process design of ultra-fine bainitic steel. [ABSTRACT FROM AUTHOR]

With the speedy development and the continuous application of special alloy manufacturing nowadays, M2 high-speed (HSS) steel is difficult to meet industrial needs. For improving the red hardness and wear resistance of M2 HSS surface, 20 wt.% Co was added into NiCrCu alloy powder and preplaced it onto the surface of M2 HSS, and then, the coating was fabricated by plasma cladding. The organization structure and mechanical properties of coatings before and after Co addition were studied. The results show that the addition of Co strengthened the matrix in the form of substitutional solid solution. Co did not change the phase composition and microstructure characteristics of the coating, but it reduced the residual stress and undesirable residual austenite content of the coating. The surface quality and crack resistance of the coating were optimized. In addition, the red hardness and wear resistance of the coating were significantly improved after adding Co. The average hardness increased by 22.53%, the average friction coefficient decreased by 21.65%, and the volume wear decreased by 56.86% after the coating tempering at 550 °C for 4 h. Moreover, the average hardness of Co-containing coating decreased slowly after tempering for different times. The present work is of great significance in providing a potential guidance for broadening the HSS application fields. [ABSTRACT FROM AUTHOR]

This paper aims to unveil effects of α colony and α plate parameters on tensile properties and impact toughness of Ti-55531 alloy with multilevel lamellar microstructures. Microstructures with different α colony and α plate sizes were prepared using varied heat treatments and analyzed by X-ray diffraction, scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy. Relationships of microstructure and strength, plasticity and impact toughness were discussed. Results indicate that tensile strength increases, while plasticity and impact toughness of the alloy decline with decreasing effective sizes (width/length ratio) of α colony (dc) and α plate (dα) and increasing of volume fraction of α phase. Both dc and dα follow the Hall–Petch principle with strength, and dc was determined to be the critical controlling parameter of strength owing to higher interfacial strengthening effect induced by α colony. However, plasticity is primarily related to dα. Moreover, impact toughness for both dc and dα follows the linear relation, but the coefficient of dα is higher. Furthermore, impact toughness is more dependent on plasticity than strength. Larger α plates lead to more mechanical twins during impacting and result in higher plasticity and impact toughness. Therefore, the impact toughness should depend more on the size of α plates. In order to unveil the influence of α plate size on impact deformation and microcrack initiation behavior of Ti-55531 alloy, the microstructural deformation and crack nucleation characteristics in the impact crack nucleation region were detected by TEM in detail; then, the schematic illustration for microstructural deformation and crack nucleation characteristics was made according to experiment results. [ABSTRACT FROM AUTHOR]

Magmatism in the Huili area (SW margin of the Yangtze block) was active during the early Mesoproterozoic, and has important implications on the early tectonic evolution of the Yangtze block. We report new data in petrology, whole-rock geochemistry, zircon U-Pb and Hf isotopes for the Yaopengzi dolerite in the Huili area. LA-ICP-MS zircon U-Pb dating of the dolerite yielded an early Mesoproterozoic age of ca. 1515–1513 Ma, coeval with the Columbia supercontinent breakup. The dolerite belongs to the alkali basalt series, and is enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), resembling typical oceanic island basalt (OIB) in geochemistry. Zircons from the Yaopengzi dolerite yielded 176Hf/177Hf = 0.28192–0.28203 and εHf(t) =–0.3 to 5.3. Our integrated study suggests that parental magma of the Yaopengzi dolerite may have originated from the enriched mantle, and was slightly contaminated by crustal materials during its evolution. Combining with regional tectonic background, the early Mesoproterozoic mafic magmatism at/ around Yaopengzi may have formed in a mantle plume-related intracontinental rift setting. This reflects that the early Mesoproterozoic extension in the Yangtze block may have resulted from mantle plume activities led by the Columbia supercontinent breakup. [ABSTRACT FROM AUTHOR]

The Binh Do Pb-Zn deposit in the Phu Luong region (Thai Nguyen Province, northern Vietnam) is located on the southern margin of the South China Block. The fault-controlled Pb-Zn orebodies are mainly hosted in Upper Paleozoic carbonate formations. In order to reveal the mineralization type and metallogenesis of this deposit, multi-isotopic (S, Pb, H and O) analyses on typical ore and gangue minerals were conducted. The average ore sulfide δ34SΣS value is 4.3‰, suggestive of magmatic sulfur. The ore sulfide Pb isotope compositions are homogeneous, with the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of 18 501 to 18 673 15.707 to 15 798, and 38 911 to 39.428, respectively. Lead isotope model ages of the ore sulfides (240-220 Ma) are consistent with the timing of regional Triassic S-type granite emplacement (250-220 Ma), suggesting that the metals may have been granite-derived. The quartz δDV-SMOW (-82.4‰ to -70.5‰) and δ18OH2O (-0.4‰ to +6.4‰) values suggest that the ore-forming fluids were composed of mixed magmatic and meteoric waters. Combined with the geological features of the Pb-Zn deposit in the region, we propose that the Pb-Zn deposits belong to magmatic-hydrothermal type, rather than MVT-type as previously suggested. The Triassic granites may have contributed the ore-forming material and heat that drove the hydro-thermal system. The ore-forming fluids may have migrated into interlayer faults and fractures of the carbonate strata, diluted by subsurface meteoric water and deposited successively the vein-type and stratiform-type Pb-Zn ores. [ABSTRACT FROM AUTHOR]

The Anjing Hitam Pb-Zn deposit in northern Sumatra (Indonesia) is one of the largest Pb-Zn deposits in the region. The stratiform orebodies are mainly hosted in the middle member of the Carboniferous-Permian Kluet Formation of the Tapanuli Group. Mineral paragenesis and crosscutting relationships suggest a two-stage Pb-Zn mineralization: (I) sedimentary and (II) hydrothermal mineralization. Ore-related calcite from both stages I and II contains mainly liquid- and gas-liquid two-phase-type fluid inclusions (FI). For stage I ore-forming fluids, FI homogenization temperatures (Th) are 105 to 199 °C, and the salinities are 9.6 wt.% to 16.6 wt.% NaCleqiv, reflecting low temperature and medium-low salinity; whereas in stage II, the Th (206 to 267 °C) and salinity (19.0 wt.% to 22.5 wt.% NaCleqiv) are considerably higher. Fluid inclusion and C-O isotope characteristics suggest that the stage I ore-forming fluids were mainly derived from a mixture of seawater and magmatic fluids (probably from deep-lying plutons), whereas the stage II ore-forming fluids were likely magmatic-derived with wall rock input. We propose that the Anjing Hitam deposit was a Carboniferous exhalative sedimentary (SEDEX) deposit overprinted by the Pleistocene vein-style magmatic-hydrothermal mineralization. [ABSTRACT FROM AUTHOR]

Loss of airway epithelial integrity contributes significantly to asthma pathogenesis. Thymic stromal lymphopoietin (TSLP) may have dual immunoregulatory roles. In inflammatory disorders of the bowel, the long isoform of TSLP (lfTSLP) promotes inflammation while the short isoform (sfTSLP) inhibits inflammation. We hypothesize that lfTSLP contributes to house dust mite (HDM)-induced airway epithelial barrier dysfunction and that synthetic sfTSLP can prevent these effects. In vitro, airway epithelial barrier function was assessed by monitoring transepithelial electrical resistance, fluorescent-dextran permeability, and distribution of E-cadherin and β-catenin. In vivo, BALB/c mice were exposed to HDM by nasal inhalation for 5 consecutive days per week to establish an asthma model. sfTSLP and 1α,25-Dihydroxyvitamin D3 (1,25D3) were administered 1 h before HDM exposure. After 8 weeks, animal lung function tests and pathological staining were performed to evaluate asthma progression. We found that HDM and lfTSLP impaired barrier function. Treatment with sfTSLP and 1,25D3 prevented HDM-induced airway epithelial barrier disruption. Moreover, sfTSLP and 1,25D3 treatment ameliorated HDM-induced asthma in mice. Our data emphasize the importance of the different expression patterns and biological properties of sfTSLP and lfTSLP. Moreover, our results indicate that sfTSLP and 1,25D3 may serve as novel therapeutic agents for individualized treatment of asthma. [ABSTRACT FROM AUTHOR]