Pu−Sn

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Pu−Sn     

O−Pb

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O−Pb     

Pb−Sn

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Pb−Sn     

Temperature-dependent R-curve behavior of Pb(Zr1−xTix)O3

The crack growth resistance behavior of polycrystalline Pb(Zr_1?xTi_x)O₃ has been characterized in a novel experimental arrangement between 24 and 140 °C. Experimental measurements were carried out on compact tension specimens submerged in a temperature-controlled silicone oil bath. The results show a decrease in the observed shielding toughness, leading to an overall reduction in the maximum toughness. The temperature-dependent stress–strain behavior and elastic properties were characterized, providing an insight into the effect of the changing ferroelastic properties on the temperature-dependent fracture behavior.     

Effect of the sample sizes and the sampling conditions on the results of chemical analysis of castings of Cu−Sn and Cu−Sn−Pb alloys

In horizontal continuous casting of semifinished products made of alloys of the Cu−Sn and Cu−Sn−Pb systems segregation of tin and lead complicates the problem of obtaining the specified composition. The aim of this work consists in determining the size of the sample and the conditions for taking it in casting for which the specified chemical composition of the casting will be uniform over the entire volume. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 34–35, October, 1998.     

New Fe−Co−Ni−Cu−Al−Ti Alloy for Single-Crystal Permanent Magnets

A new alloy intended for single-crystal permanent magnets has been suggested. The new alloy has been designed based on the well-known Fe?Co?Ni?Cu?Al?Ti system and contains to 1 wt % Hf. The alloy demonstrates an enhanced potential ability for single-crystal forming in the course of unidirectional solidification of ingot. Single-crystal permanent magnets manufactured from this alloy are characterized by a high level of magnetic properties. When designing the new alloy, computer simulation of the phase composition and calculations of solidification parameters of complex metallic systems have been performed using the Thermo-Calc software and calculation and experimental procedures based on quantitative metallographic analysis of quenched structures. After the corresponding heat treatment, the content of high-magnetic phase in the alloy is 10% higher than that in available analogous alloys.     

Evidence of fluid evolution of Baoshan Cu−Pb−Zn polymetallic deposit: Constraints from in-situ sulfur isotope and trace element compositions of pyrite

In-situ LA-ICP-MS and S isotopes of pyrite from the Baoshan Cu polymetallic deposit were conducted to investigate the ore-forming process and the enrichment mechanism of elements. Three generations of pyrite (Py I, Py II, and Py III) in the skarn-type ores and pyrite in the carbonate-hosted sulfide ores from central, western, and northern (C_Py, W_Py, and N_Py) mining districts are selected for comparison. Compared with Py I and Py III, the contents of most elements in Py II are apparently higher. The As and Se contents are high within a wide range and are decoupled in the growth band of the C_Py. The highest As, Se, and Pb contents were found in W_Py and N_Py. These results indicate the drastic changes in the temperature and fluid mixing during the mineralization. The occurrence of fluctuation and change in temperature and f(O₂) was triggered by intermittent pulses of magmatic-hydrothermal fluids, mixing with meteoric water, and water−rock interactions. The sulfur isotopes of all species of pyrite indicated the magmatic source. The change in the f(O₂) conditions caused slight differences in the sulfur isotope compositions. Consequently, a metallogenic model was proposed to explain the ore-forming processes.     

Phases and thermoelectric properties of Ge1−x(Pb0.9Yb0.1)xTe alloys

A series of Ge_1−x(Pb_0.9Yb_0.1)_xTe alloys with x = 0.05, 0.10, 0.15, 0.20 and 0.30 were prepared by a conventional melting and a spark plasma sintering (SPS) techniques. The phases and thermoelectric properties for the alloys were investigated. The alloys consist of the GeTe-based rhombohedral single phase for x = 0.05, while both GeTe-based rhombohedral and PbTe-based rock-salt phases due to spinodal decomposition for the higher Pb content (x ≥ 0.10). The amount of the PbTe-based phase increases with the Pb content x increasing. All samples show p-type conduction. As Pb content x increases, the thermal conductivity reduces obviously, while the Seebeck coefficient and the electrical resistivity increases slightly. The maximum ZT of 1.4 at 723 K was eventually achieved in the sample with x = 0.15 due to its rather low thermal conductivity, from 3.7 W m⁻¹K⁻¹ at room temperature to 1.4 W m⁻¹K⁻¹ at 723 K (3.7–1.4 W m⁻¹K⁻¹), relative high Seebeck coefficient (46.5–141 μV K⁻¹) and relative low electrical resistivity (3.0–7.36 μΩ m).     

Microstructure and shear strength of γ-TiAl/GH536 joints brazed with Ti−Zr−Cu−Ni−Fe−Co−Mo filler alloy

The influence of brazing temperature and brazing time on the microstructure and shear strength of γ-TiAl/GH536 joints brazed with Ti−Zr−Cu−Ni−Fe−Co−Mo filler was investigated using SEM, EDS, XRD and universal testing machine. Results show that all the brazed joints mainly consist of four reaction layers regardless of the brazing temperature and brazing time. The thickness of the brazed seam and the average shear strength of the joint increase firstly and then decrease with brazing temperature in the range of 1090−1170 °C and brazing time varying from 0 to 20 min. The maximum shear strength of 262 MPa is obtained at 1150 °C for 10 min. The brittle Al₃NiTi₂ and TiNi₃ intermetallics are the main controlling factors for the crack generation and deterioration of joint strength. The fracture surface is characterized as typical cleavage fracture and it mainly consists of massive brittle Al₃NiTi₂ intermetallics.     

不同尺寸Mg−Gd−Y−Zn−Ag镁合金零件冷却后的腐蚀行为

研究不同尺寸的Mg?6Gd?3Y?1Zn?0.3Ag(质量分数,％)镁合金零件冷却后的腐蚀行为.小型零件冷却较快,其显微组织由镁基体和粗大的长周期堆垛有序结构(LPSO)相组成.大型零件冷却较慢,其显微组织除镁基体和粗大的LPSO相外,晶粒内部有薄片状LPSO相析出.析氢测试结果表明,大型零件的腐蚀速度高于小型零件.交...     

Synergistic depression mechanism of zinc sulfate and sodium dimethyl dithiocarbamate on sphalerite in Pb−Zn flotation system

The depression mechanism of zinc sulfate (ZnSO₄) and sodium dimethyl dithiocarbamate (DMDC) as the combined depressant on sphalerite was investigated by micro-flotation experiments, ion complexing tests, contact angle tests and X-ray photoelectron spectroscopy (XPS) analysis. The micro-flotation tests revealed that ZnSO₄+DMDC had a better selective depression effect on sphalerite than using single ZnSO₄ or DMDC. Ion complexing tests confirmed that DMDC had a strong complexing capacity with lead ions or hydroxy complexes. Contact angle tests illustrated that ZnSO₄+DMDC makes the sphalerite surface more hydrophilic than ZnSO₄ or DMDC. XPS analysis indicated that the combined depressant could prevent collector adsorbing on the Pb-activated sphalerite surface by a competitive adsorption method, while the combined depressant and collector were co-adsorbed on galena surface.     

Carbon nanotubes grown over Fe−Mo−Mg−O composite catalysts

High quality, high yield carbon nanotubes were synthesized on a composite catalyst using catalytic chemical vapor deposition. The composite catalysts Fe/MgO, Mo/MgO and (Fe, Mo)/ MgO, prepared via the solgel method using citric acid as fuel, were investigated for the production of CNTs. Only the (Fe, Mo)/MgO catalyst could support CNTs growth with high yield in this study. The different mole ratios between Fe, Mo, and Mg resulted in changes in product structure, diameter size, and yield. Decreasing the Fe concentration reduces the structural defects, and by increasing the Mo concentration, the yields of CNTs clearly increase.     

Correlation between the oxide impedance and corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys

The correlation between the oxide impedance and corrosion behavior of two series of Zr−Nb−Sn−Fe−Cu alloys was evaluated. Corrosion tests were performed in a 70 ppm LiOH aqueous solution at 360°C for 300 days. The results of the corrosion tests revealed that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers. The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for evaluating the long-term corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys.     

Amorphous phase formation in a Ni−Zr−Al−Y alloy system

Quaternary Ni-based amorphous alloys containing only metallic elements were developed through systematic alloy design. The importance of the phase equilibria information for the development of amorphous alloys was demonstrated through experimental results. Ni−Zr−Al ternary alloys having low liquidus temperature tend to have high GFA. Partial replacements of Zr with Y in the ternary alloys significantly enhanced the GFA of the quaternary alloys. The alloy Ni₆₀Zr₂₅Al₈Y₇ could be cast into a fully amorphous rod through an injection casting method. Since most Ni-based amorphous alloys reported to date contain non-metallic elements, the Ni-based amorphous alloys developed in the alloy system Ni−Zr−Al−Y are of interest.     

脆性岩石热−水−力−化学(THMC)耦合断裂准则

通过分析脆性岩石THMC耦合机理,选取岩石孔隙率作为THMC耦合因子来表征THMC耦合场对应力场的影响.提出一种实时监测岩石渗透率(与孔隙率相关)的新型测试方法以确定THMC耦合因子.利用自行设计的THMC耦合试验和断口电镜扫描试验研究预制裂隙红砂岩宏观和微观断裂机理.结果表明:水压越高,围压越低,起裂荷载越小,I型断...     

Hydrogen permeation properties of Pd-coated Ni−Nb−Ti−Zr amorphous alloys

Hydrogen permeability of Pd-coated Ni₆₀Nb₁₅Ti₁₅Zr₁₀ and Ni₆₀Nb₂₀Ti₁₅Zr₅ amorphous alloys was measured in the temperature range of 673 K to 773 K and was compared with the results obtained using Ni₆₀Nb₄₀, a binary amorphous alloy. The permeability thus measured was found to increase moderately increasing temperature. A long-term permeation test for the Pd-coated Ni₆₀Nb₁₅Ti₁₅Zr₁₀ amorphous alloy revealed high permeation stability up to 16.6 h.     

Refinement and strengthening mechanism of Mg−Zn−Cu−Zr−Ca alloy solidified under extremely high pressure

Mg?Zn?Cu?Zr?Ca samples were solidified under high pressures of 2–6 GPa. Scanning electron microscopy and electron backscatter diffraction were used to study the distribution of Ca in the microstructure and its effect on the solidification structure. The mechanical properties of the samples were investigated through compression tests. The results show that Ca is mostly dissolved in the matrix and the Mg₂Ca phase is formed under high pressure, but it is mainly segregated among dendrites under atmospheric pressure. The Mg₂Ca particles are effective heterogeneous nuclei of α-Mg crystals, which significantly increases the number of crystal nuclei and refines the solidification structure of the alloy, with the grain size reduced to 22 μm at 6 GPa. As no Ca segregating among the dendrites exists, more Zn is dissolved in the matrix. Consequently, the intergranular second phase changes from MgZn with a higher Zn/Mg ratio to Mg₇Zn₃ with a lower Zn/Mg ratio. The volume fraction of the intergranular second phase also increases to 22%. Owing to the combined strengthening of grain refinement, solid solution, and dispersion, the compression strength of the Mg–Zn–Cu–Zr–Ca alloy solidified under 6 GPa is up to 520 MPa.