Radiation damage of 1Cr18Ni9Ti and Zr-Ti-Al alloys due to energetic particle irradiation

The radiation damage of 1Cr18Ni9Ti stainless steel and the Zr-Ti-Al alloy by 200 keV Xe+ ions bombardment at the fluence ranging from 1×1014 to 8×1015 ions/cm2 has been investigated by conventional transmission electron microscope, X-ray diffraction line profile analysis (XRDLPA) and nanoindentation. XRDLPA shows that the order of magnitude of dislocation density in both materials remains almost unchanged up to the highest irradiation dose. Selected-area electron diffraction combined with bright and dark field image indicates that 1Cr18Ni9Ti is more easily damaged than the Zr-Ti-Al alloy. With increasing the ions fluence, the radiation damage became more severe in 1Cr18Ni9Ti, accompanied with phase transition and partial amorphization. The nano-hardness was found to increase rapidly with increasing ion fluence till the dose of 1×1015 ions/cm2, and then gradually saturate with dose. The enhancement of hardness in irradiated materials is due to irradiation-induced defects acting as barriers to dislocation motion.     

A Newly Developed Wrought Ni–Fe–Cr-based Superalloy for Advanced Ultra-Supercritical Power Plant Applications Beyond 700℃

Some existing wrought Ni–Cr–Co-based superalloys are being evaluated as the candidate materials for advanced ultra-supercritical power plant applications beyond 700 ℃ due to their high creep strength. But they are all prohibitively expensive due to the addition of Co, Mo and W. Here we developed a new Ni–Fe–Cr-based superalloy(named as HT700 alloy) with low cost and high strength. This paper reports the mechanical properties and fracture modes of HT700 alloy to support its high temperature applications and to understand prospective failure mechanism. Fractographic examinations indicate that the fracture modes shift with test condition change. In addition, the HT700 alloy has relatively stable microstructure at 750 ℃. Compared with IN740 and GH2984 alloys, this new alloy has higher yield strength in the temperature range from room temperature to 800 ℃. The creep life of this new alloy is much longer than that of the Ni–Fe-based superalloy GH2984. The results suggest that this new alloy is a promising material for advanced ultra-supercritical power plant applications beyond 700 ℃.     

Thermodynamic Characteristic and Phase Evolution in Immiscible Cr–Mo Binary Alloys

This paper systematically reports the thermodynamic characteristic and phase evolution of immiscible Cr–Mo binary alloy during mechanical alloying(MA) process. The Cr–35Mo(in at%) powder mixture was milled at 243 and258 K, respectively, for different time. For comparative study, Cr–15Mo and Cr–62Mo powder mixtures were milled at 243 K for 18 h. Solid solution Cr(Mo) with body-centered cubic(bcc) crystal structure and amorphous Cr(Mo) alloy was obtained during MA process caused by high-energy ball milling. Based on the Miedema's model, the free-energy change for forming either a solid solution or an amorphous in Cr–Mo alloy system is positive but small at a temperature range between 200 and 300 K. The thermodynamical barrier for forming alloy in Cr–Mo system can be overcome when MA occurs at 243 K, and the supersaturated solid solution crystal nuclei with bcc structure form continually, and three supersaturated solid solutions of Cr–62Mo, Cr–35Mo and Cr–15Mo formed. Milling the Cr–35Mo powder mixture at 258 K, the solid solution Cr(Mo) forms firstly, and then the solid solution Cr(Mo) transforms into the amorphous Cr(Mo)alloy with a few of nanocrystallines when milling is prolonged. At higher milling temperature, it is favorable for the formation of the amorphous phase, as indicated by the thermodynamical calculation for immiscible Cr–Mo alloy system.     

Valence electron structures and properties of Ni-based corrosion resistant alloy

The corrosion resistance and mechanical properties were tested and compared for the newly synthesized as-cast, as-solution Ni-Cr-Mo-Cu corrosion resistant alloys and 1Cr18Ni9Ti austenitic stainless steel. Their valence electron structural units were constructed, and the relative parameters were calculated by means of the Empirical Electron theory of Solids and Molecules （EET）. The results show that, during alloy elements Cr, Mo and Cu entering Ni-matrix, the bonding strength nA and bonding energy EA of the strongest bond of the alloy are greatly increased, causing the stronger solid solution strengthening effects （about 30% increase in σb）. Also, as reinforcement of the main bond network and the improvement of stability of the alloy system due to the solution of these alloying elements in γ-Ni, the ionization of metal atoms in corrosion solution and the flow of electrons from anode to cathode would all be impeded during electro-chemical corrosion processes, which leads to the excellent corrosion resistant ability of the present Ni-Cr-Mo-Cu alloy （about 2-3 orders of magnitude as high as 1Cr18Ni9Ti austenitic stainless steel） in several highly aggressive solutions.     

Effect of Surface Layer Structural-Phase Modification on Tribological and Strength Properties of a TiC–(Ni–Cr) Metal Ceramic Alloy

This paper reports TiC–(Ni–Cr) metal ceramic alloy(ratio of components 50:50) with nanoscaled components formed in the surface layer and smoothly transformed into the initial inner structure throughout the material under pulsed electron irradiation of the alloy surface. Principal changes in the surface layer are ascribed to the formation of gradient structure leading to the increase in wear resistance of the surface layer, drop of friction coefficient and improvement of specimen bending resistance when stressing on the irradiated surface side. The above changes of tribological and strength properties in the surface layer under pulsed electron irradiation become more apparent with increasing atomic mass of a plasma-forming inert gas.     

Dynamic response and plastic deformation behavior of Ti–5Al–2.5Sn ELI and Ti–8Al–1Mo–1V alloys under high-strain rate

Split Hopkinson pressure bar test system was used to investigate the plastic deformation behavior and dynamic response character of a-type Ti–5Al–2.5Sn ELI and near a-type Ti–8Al–1Mo–1V titanium alloy when subjected to dynamic loading. In the present work, stress–strain curves at strain rate from 1.5 9 103to 5.0 9 103s-1were analyzed, and optical microscope(OM) was used to reveal adiabatic shearing behavior of recovered samples. Results show that both the two alloys manifest significant strain hardening effects. Critical damage strain rate of the two alloys is about 4.3 9 103s-1, under which the impact absorbs energy of Ti–5Al–2.5Sn ELI and Ti–8Al–1Mo–1V are 560 and 470 MJ m-3, respectively. Both of them fracture along the maximum shearing strength orientation, an angle of 45° to the compression axis. No adiabatic shear band(ASB) is found in Ti–5Al–2.5Sn ELI alloy, whereas several ASBs with different widths exist without regular direction in Ti–8Al–1Mo–1V alloy.     

Precipitate Behavior in Fe–20Cr–30Ni–2Nb Austenitic Heat-Resistant Steel

In this study,the precipitation behavior of a new austenitic heat-resistant steel(Fe–20Cr–30Ni–2Nb,in at%)was investigated.The effects of alloying addition of boron(B) and lanthanum(La) on the microstructure of the austenitic steel were scrutinized using SEM,EPMA,TEM,and XRD.The results showed that the addition of B enhanced the precipitation of bar-type Laves phase.A small precipitate with high La concentration was observed at the grain boundary in the alloy without aging;similar precipitates without La also presented in region adjacent to the La single phase.This result indicates that La can exist independently and does not contribute to the formation of new compounds.However,in both Band La-modified alloy,B appeared in the precipitate free zone.In the alloy containing both B and La,only Fe2 Nb Lavesphase precipitates,as indicated by the XRD result.     

Enhanced Electromagnetic Interference Shielding of Mg–Zn–Zr Alloy by Ce Addition

The effects of Ce addition on microstructure and electromagnetic interference(EMI) shielding response of Mg–6Zn–0.5Zr(ZK60) alloy have been investigated.Ce addition resulted in grain refinement and higher density of Mg–Zn–Ce and Mg Zn2 intermetallic particles in the alloy.In particular,this was substantially remarkable as the addition of Ce was up to 1.0 wt%.It is interesting to note that as-extruded ZK60 alloy with 1.0 wt% Ce addition exhibited an EMI shielding effectiveness(SE) exceeding 70 d B at the frequency range of 30–1,500 MHz,which was significantly higher than that of ZK60 alloy without Ce addition and reached the requirement of high protection.The superior SE was probably related to the increased reflection and multiple reflection of electromagnetic radiation induced by Ce addition.Direct artificial aging at 150 °C for 25 or 50 h led to a further increase of 7–10 d B in the SE of the alloy with 1.0 wt% Ce addition.The advantages of excellent shielding capacity and favorable mechanical strength make the Mg–Zn–Zr–Ce alloy an attractive shielding candidate material for a variety of technological applications.     

Effect of Mo Addition on the Microstructure and Properties of TiNiNb Alloy

The influence of Mo addition on the microstructure and properties of TiNiNb alloy with 4.5 at.% Nb has been investigated systemically.The experimental results indicated that the uniform distribution of Mo depresses the appearance of coarse b-Nb particles at the grain boundaries and short stripped texture consisting of abundant fine disperse Nb-rich particles appears around the grain boundaries.The yield strength of the alloy was enhanced from 450 to 600 MPa due to the solution strengthening of Nb and Mo and the elongation reached 18% when the Mo content is 0.5 at.%.At the same time,the shape memory effect of the alloy also is improved significantly by the Mo addition.The maximum recoverable strain of the alloy with 0.5 at.% Mo is near 8% and has reached the high level of Ni–Ti binary alloys.This novel highstrength alloy is promising to be used for high pressure tube and the macro-scale coupling with higher-quality requirements.     

Dynamic recrystallization behavior of Fe–20Cr–30Ni–0.6Nb–2Al–Mo alloy

Single-pass compression tests of an aluminaforming austenite(AFA) alloy(Fe–20Cr–30Ni–0.6Nb–2Al–Mo) were performed using a Gleeble-3500 thermal–mechanical simulator. By combining techniques of electron back-scattered diffraction(EBSD) and transmission electron microscopy(TEM), the dynamic recrystallization(DRX) behavior of the alloy at temperatures of 950–1100 ℃ and strain rates of 0.01–1.00 s~(-1) was investigated. The regression method was adopted to determine the thermal deformation activation energy and apparent stress index and to construct a thermal deformation constitutive model. Results reveal that the flow stress is strongly dependent on temperature and strain rate and it increases with temperature decreasing and strain rate increasing. The DRX phenomenon occurs more easily at comparably higher deformation temperatures and lower strain rates. Based on the method for solving the inflection point via cubic polynomial fitting of strain hardening rate(h) versus strain(e) curves, the ratio of critical strain(ec) to peak strain(ep) during DRX was precisely predicted. The nucleation mechanisms of DRX during thermal deformation mainly include the strain-induced grain boundary(GB)migration, grain fragmentation, and subgrain coalescence.     

Electrochemical Behavior of Passive Films Formed on the Surface of Coarse-,Fine-and Ultra-fine-Grained AA1050 Based on a Modified PDM

Electrochemical impedance spectroscopy(EIS) and Mott-Schottky analysis were carried out to evaluate the electrochemical behavior of the passive films formed on the surface of coarse-grained(CG),fine-grained(FG) and ultrafine-grained(UFG) 1050 Al alloy(AA1050) samples in alkaline media(pH value of 8.0) based on a modification of point defect model(PDM).The EIS results revealed that the polarization resistance increased from about 22.71-120.33 kΩ cm~2for UFG sample when compared to CG sample(annealed sample).The semiconductor properties of the passive films formed on CG,FG and UFG AA1050 samples in the test solution were investigated by employing Mott-Schottky analysis in conjunction with PDM.The results indicated that donor densities were in the range of 2.19 × 10~(21)-0.61 × 10~(21) cm~(-3)and decreased with grain refinement.Finally,all electrochemical tests showed that the electrochemical behavior of AA1050 alloy was improved by decreasing the grain size,mainly due to the formation of thicker and less defective oxide films.     

Portevin–Le Chatelier Effect in Nimonic 263 Superalloy

The Portevin–Le Chatelier(PLC) effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 9 10-6s-1. Simple binary alloys Ni-0.4C, Ni-24 Cr and Ni-5(8)Mo were also tested in order to identify which elements were responsible for the PLC effect in the Nimonic 263 alloy. The results demonstrated that for Nimonic 263 alloy, PLC effect occurred at certain temperatures and low strain rates. Normal PLC effect exhibiting type-A and-(A + B) serrations was attributed to the enhanced solute diffusion with increasing temperature, while inverse PLC effect with type-C serration was caused by unlocking process.The activation energy for the normal PLC effect was calculated to be 68 k J/mol, and diffusion of substitutional solutes such as Cr and Mo was identified to be responsible for the PLC effect. In comparison with the PLC effect in simple binary alloys, solute atmospheres formed by different kinds of atoms in Nimonic 263 alloy work more effectively, increasing locking strength and corresponding mean stress drop magnitude.     

碳钢超声磷化及在模拟干热岩地热水中的耐蚀性能

采用环境友好的硫酸羟胺为主要促进剂,避免使用强氧化性物质,并以超声处理来改进磷化工艺。通过动电位极化曲线方法研究了超声、促进剂、pH值和磷化时间对磷化膜耐蚀性能的影响。结果表明,超声处理能够细化磷化颗粒,提高其耐蚀性能。pH值和磷化时间显著影响磷化膜的耐蚀性,需保持在较优的范围。采用电化学阻抗谱研究了优化工艺得到的磷化膜在模拟干热岩地热水中的耐蚀性,发现其电荷转移电阻由碳钢的1.44×10³ Ωcm²增加到3.39×10⁶ Ωcm²。     

Thermally and Optical-Induced Effect on Optical and Electrical Parameters of Ag-Doped CdSe Thin Films

Thin films of Ag-doped Cd Se are deposited on the glass substrates by thermal evaporation technique using inert gas condensation method. The elemental composition of the prepared thin film is confirmed by EDX spectra. SEM analysis reveals the uniform distribution of the grains over the substrate. TEM analysis reveals the spherical nature of nanoparticles having size in the range of 25–30 nm. X-ray diffraction study indicates an increase in the grain size after thermal annealing and the decrease in the grain size after light soaking treatment. Transmittance spectra are found to decrease with corresponding red shift after annealing and light soaking of as-deposited thin films. The value of the band gap is found to decreases and refractive index increases, after annealing and light soaking treatment. The dispersion of refractive index is described using the Wemple–Di Domenico single oscillator model and the effects of the annealing and the light soaking on the dispersion parameters are studied. The dark conductivity is found to change from 2.24 9 10-8to 1.54 9 10-7and1.45 9 10-9X-1cm-1after annealing and light soaking of thin films, respectively. Hall effect measurement reveals n-type behavior of as-deposited, annealed and light-soaked thin films.     

氧化甾醇抑制血管平滑肌细胞(VSMC)增殖及诱导其凋亡的作用1

目的: 研究 3β, 5α, 6β-胆甾烷三醇(Triol) 和25-羟胆固醇(25OH) 对 VSMC 增殖的影响, 探讨氧化甾醇在动脉粥样硬化(AS) 发病中的作用和意义。 方法: 培养和鉴定新西兰白兔主动脉 VSMC; 以含不同浓度的Triol 和 25OH 的培养液作用于VSMC 为实验组, 不含氧化甾醇或含胆固醇的培养液作为对照组。 VSMC 增殖及其代谢活性以 WST-1 测定, 细胞凋亡以光镜、透射电镜、脱氧核苷酸末端转移酶介导脱氧尿苷三磷酸缺口末端标记(TUNEL) 判断。结果: 在1×10^-9 ~ 1 ×10^-7mol^·L^-1 范围的 Triol 和 25OH 对VSMC 的 WST-1代谢活性无明显变化(P >0.05), 而≥1×10^-6mol^·L^-1 的氧化甾醇则使其代谢活性显著下降 (P <0.01); ≥20 ×10^-6 mol^·L^-1 的 Triol 和25OH 诱导VSMC 胞体皱缩变小、染色质在核周边浓集、核碎裂、 空泡和凋亡小体形成等超微结构变化; TUNEL 呈阳性反应。结论: 小剂量氧化甾醇无促进VSMC 增殖而较大剂量氧化甾醇可诱导 VSMC 凋亡。     

山莨菪碱抑制成年大鼠离体心室肌细胞钙瞬变和收缩及其机制

目的: 观察山莨菪碱对大鼠离体心室肌细胞钙瞬变和收缩功能的影响并探讨其机制。方法: 采用单细胞动缘探测系统和双激发荧光光电倍增系统观察山莨菪碱对大鼠离体心室肌细胞钙瞬变和收缩功能的影响, 应用信号转导通路中相关受体的激动剂或拮抗剂探讨其作用机制。结果: 山莨菪碱1 ×10^-9 、1 ×10^-7 、1 ×10^-5 mol·L^-1可直接抑制心室肌细胞钙瞬变和收缩功能;卡巴胆碱可以消除山莨菪碱的作用, 而IP₃ 受体阻断剂肝素(1 ×10^-6 mol·L^-1) 和细胞膜电压依赖型钙离子通道阻滞剂维拉帕米(1 ×10^-6 mol·L^-1) 可以减弱山莨菪碱的作用。结论: 山莨菪碱抑制心室肌细胞钙瞬变和收缩功能可能与其阻断M 受体、抑制细胞内钙库钙离子释放和经过电压依赖型钙离子通道的钙离子内流有关。     

冷轧对G20CrNi2MoA渗碳轴承钢组织演变与耐磨性的影响

采用电子背散射衍射分析(EBSD)、扫描电镜(SEM)、X射线能谱分析(EDS)等方法研究了冷轧对G20CrNi2MoA渗碳轴承钢微观组织演变规律和耐磨性的影响。结果表明:冷轧能够细化原材料晶粒;当冷轧变形量由0%增加到30%时,经二次淬火后,表层碳化物面积分数由4.38%增加到5.99%,碳化物平均粒径由0.15 μm降低到0.13 μm;经二次低温回火后,表层约0.9 mm渗碳层深范围内碳含量梯度和显微硬度梯度得到提高,平均摩擦因数由0%的0.489降低到30%变形量下的0.346,磨损率由27.2×10^-6 mm³·N^-1·m^-1降低到9.1×10^-6 mm³·N^-1·m^-1。表明材料经30%冷轧变形后,由于表层碳化物的面积分数和硬度得到提高,磨粒磨损和疲劳磨损逐渐减轻,使耐磨性得到提高。     

新一代胸苷酸合成酶抑制剂ZD1694 的体内外抗肿瘤作用

目的: 观察ZD1694 对小鼠体内S180 肉瘤生长的抑制作用及其在体外对人胃腺癌SGC-7901 细胞增殖的影响。方法: 采用荷瘤小鼠模型, 腹腔注射不同剂量的ZD1694, 分单次给药与连续5 d 分次给药两种方案。处死动物后称取肿瘤组织重量, 计算抑瘤率。另外采用MTT 比色法及流式细胞仪观察ZD1694 对人SGC-7901 胃腺癌细胞株生长的影响。结果: ZD1694 可抑制小鼠体内S180 肉瘤的生长, 其抑瘤率无论是单次给药组(200 、100 、50 mg·kg^-1) 还是连续5 d 给药组(40 、20 、10 mg·kg^-1 ·d^-1), 均可见剂量依赖性增加。ZD1694(0.001 ~ 1 000 mmol·L^-1)对SGC-7901 人胃腺癌细胞的生长抑制率呈浓度依赖性和时间依赖性增加, 可使G₀-G₁ 期细胞增多,S 期和G₂-M 期细胞减少。结论: ZD1694 对荷瘤小鼠产生明显的抗瘤作用, 一次性给药的抑瘤率大于相同剂量分5 次给药的抑瘤率。该药在体外可抑制人胃腺癌SGC-7901 细胞生长, 使细胞发生G₁ 期阻滞。     

Selective Laser Melting of Al-7Si-0.5 Mg-0.5Cu: Effect of Heat Treatment on Microstructure Evolution,Mechanical Properties and Wear Resistance

Al-7Si-0.5 Mg-0.5Cu alloy specimens have been fabricated by selective laser melting (SLM). In this study, the effects of solution treatment, quenching, and artificial aging on the microstructural evolution, as well as mechanical and wear properties, have been investigated. The as-prepared samples show a heterogeneous cellular microstructure with two different cell sizes composed of α-Al and Si phases. After solution-treated and quenched (SQ) heat treatment, the cellular microstructure disappears, and coarse and lumpy Si phase precipitates and a rectangular Cu-rich phase were observed. Subsequent aging after solution-treated and quenched (SQA) heat treatment causes the formation of nanosized Cu-rich precipitates. The as-prepared SLMs sample has good mechanical properties and wear resistance (compressive yield strength: 215 ± 6 MPa and wear rate 2 × 10^-13 m³/m). The SQ samples with lumpy Si particles have the lowest strength of 167 ± 13 MPa and the highest wear rate of 6.18 × 10^-13 m³/m. The formation of nanosized Cu-rich precipitates in the SQA samples leads to the highest compressive yield strength of 233 ± 6 MPa and a good wear rate of 5.06 × 10^-13 m³/m.     

国产头孢丙烯颗粒剂人体药代动力学和生物等效性研究

目的: 建立HPLC-UV 法同时测定人血浆中的顺式和反式头孢丙烯,对国产头孢丙烯颗粒剂和胶囊剂进行人体药代动力学研究和人体相对生物等效性研究。方法: 将20 名健康志愿者分两组进行单剂量双交叉试验,剂量均为500 mg,两次试验间隔时间为7d 。血浆样品用20 %的三氯醋酸沉淀蛋白后,用乙腈和二氯甲烷的混合溶剂提取内源性杂质,离心后取上清液进样分析;色谱柱为LichrospherC8 柱(5μm,4.6 mm×30 cm),流动相为乙腈-1.5 %的乙酸水溶液(15∶85),流速:1.0 ml·min^-1,检测波长:280 nm,柱温为30 ℃,内标为头孢拉定。结果: 血浆中杂质不干扰样品的测定,标准曲线范围为0.0209~ 10.47 mg·L^-1,线性关系良好(r=0.9993),最低定量限为0.0209 mg·L^-1;参比制剂与受试制剂的达峰时间分别为1.7±0.3 h,1.8±0.2 h;达峰浓度分别为:4.45±1.25 mg·L^-1 、4.88±1.08 mg·L^-1,生物半衰期分别为1.89±0.45 h 和1.79±0.39 h,用梯形法计算所得的AUC_0-12 分别为:12.11±2.62mg·L-1·h^-1 、12.34±2.93 mg·L^-1·h^-1,头孢丙烯受试制剂的相对生物利用度为:(101.9±8.8)%。结论: 本分析方法操作简便,结果准确可靠。对C_max 、AUC_0-12经对数转换,方差分析后进行双单侧检验及90 %可信限判断,两制剂具有生物等效性。