High temperature thermodynamic properties of solid ta-w alloys

The partial molar and integral molar thermodynamic properties of solid Ta-W alloys have been determined between 1050 and 1300 K using galvanic cells with a thoria-based electrolyte. The activities in this system exhibit negative deviations from ideality, but the magnitude of the negative deviation is less than that observed previously for the Ta-Mo alloys. The negative excess free energies of mixing are due mainly to the enthalpies of mixing. The observed small negative excess entropies of mixing can be attributed to vibrational contributions and/or short range ordering in these alloys. Graduate Student, School of Metallurgy and Materials Science, University of Pennsylvania, Philadelphia, Pa. 19104, School of Metallurgy and Materials Science, University of Pennsylvania.     

Cu-Ni-Ti合金高温热变形行为及热加工图

采用MMS-100热力模拟机对Cu-Ni-Ti合金进行了温度为700～850℃、变形速率为0.01～10 s-1的等温压缩试验.研究表明,流变应力随应变程度增加快速上升至极限值后逐渐转变为平缓曲线,随温度增加而降低,随应变速率增加而上升.基于应力与变形速率和应变温度之间的关系,构建了Cu-Ni-Ti合金的本构方程和热加...     

高碳钢连铸板坯高温力学性能

采用Gleeble-1500热模拟试验机测量了高碳钢连铸板坯的高温力学性能,得到了第Ⅰ、第Ⅲ脆性温度区的温度范围.结果表明:第Ⅰ脆性温度区脆化的主要原因是晶界部位的低熔点物质在高温下首先熔化,从而导致试样沿晶界开裂;第Ⅲ脆性温度区脆化的主要原因是在奥氏体部位析出的网状铁素体导致试样沿晶界开裂;在奥氏体单相区,由于氮化铝的析出导致钢种的塑性恶化.     

Test temperature and strain rate effects on the properties of a tungsten heavy alloy

Liquid phase sintered tungsten heavy alloy specimens with a 90W-7Ni-3Fe composition were tested for temperature and strain rate effects on mechanical behavior. Both fracture stress and strain were measured for samples tested at 20, 300, or 600 °C, with crosshead speeds ranging from 0.004 to 400 mmJs in an argon atmosphere. Fracture surface examinations showed a dramatic increase in tungsten cleavage as the ductility increased. The effect of an increasing strain rate is a slight strength increase with a concomitant ductility decrease. Alternatively, higher test temperatures degrade strength with a nonsystematic effect on ductility; maximum ductility occurs at 300 °C and a slow strain rate. Surface oxidation at 600 °C greatly degrades ductility. The results are mathematically modeled using classic strain rate dependent equations.     

M2高速钢的高温力学性能

在Gleeble- 3800热模拟机上进行了高速工具钢W6Mo5Cr4V2（M2）钢热模拟试验,测试了从650℃到1250℃温度M2钢的高温力学性能,得到了抗拉强度曲线和热塑性曲线,观察了不同温度下试样的金相组织和断口形貌。试验结果表明：M2高速钢的零塑性温度为1220℃,零强度温度为1250℃。良好的塑性温度区为950~1150℃,脆性区主要为1175℃至熔点,在850~950℃存在一个较弱的脆性区。在800℃附近,还存在一个良好的低温超塑性区。分析表明,M2高速钢的高温力学性能与基体组织的相变、碳化物的溶解和低熔点碳化物的熔化有很大关系。     

齿轮钢SAE8620H高温变形行为及热加工图

通过高温压缩试验研究齿轮钢SAE8620H在950~1100℃、应变速率0.01~10 s^-1条件下的高温变形行为.该合金钢的流动应力符合稳态流变特征,流变应力随变形温度升高以及应变速率降低而减小,其本构方程可以采用双曲正弦方程来描述.基于峰值应力、应变速率和温度相关数据推导出SAE8620H高温变形激活能Q=280359.9 J·mol^-1.根据变形量40%和60%下应力构建该齿轮钢的热加工图,通过热加工图中耗散值及流变失稳区确定其热变形工艺参数范围.SAE8620H钢在在变形程度较小时宜选取低的应变速率进行成形,而在变形程度大时则要选取低温低应变速率或者高温高应变速率.     

Acute central effects of 5,6-dihydroxytryptamine in fowl

In adult hens (Gallus domesticus) infusion into the IIIrd cerebral ventricle of 5,6-DHT (50, 75 and 100 mug) produced, after 5-10 min behavioural and electrocortical sedation and sleep lasting about 6-8 hr,and a monophasic or biphasic increase in body temperature for about 8 hr, Two and a half hr after 5,6-DHT administration, the histochemical picture showed a sustained decrease in yellow and green fluorescence in areas adjacent to the IIIrd ventricle, in the anterior hypothalamus and in the preoptic area, whereas no significant changes were detected in fluorescence of the tegmental cell-bodies. The present experiments suggest that behavioural and electrocortical effects evoked by 5,6-DHT seem to be due to a synergistic action of 5-HT and catecholamines displaced and released by this compound, whereas hyperthermic effects seem to be due to a more sustained release of 5-HT and/or to a direct action on 5-HT receptors and/or inhibition of 5-HT reuptake.     

The effects of mitomycin-C and temperature on dynamical properties of human erythrocyte membrane

We investigated the mode of action of a new quinoline derivative, TAK-603 (ethyl 4-(3,4-dimethoxyphenyl)-6,7-dimethoxy-2-(1,2,4-triazol-1-ylmeth yl) quinoline-3-carboxylate), in adjuvant arthritis (AA), a model of rheumatoid arthritis. AA rat splenocytes transferred the arthritis to normal syngeneic rats upon inoculation, but the cells from AA rats treated with TAK-603 (6.25 mg/kg/day) caused only mild arthritis with significantly less foot pad swelling and a lower arthritis score. An effect of TAK-603 in the induction phase of AA was suggested. TAK-603 had little effect on CD4+ and CD8+ T-cell populations in the AA rat splenocytes. We therefore estimated the frequency of T-cells which are reactive to the so-called disease causative antigen using a limiting dilution assay (LDA). The ratio of T-cells responsive to PPD, which increased in AA rat splenocytes with the severity of the arthritis, was reduced in AA rats treated with TAK-603. Furthermore, the ratio of MBP (myelin basic protein)-reactive T-cells, which were generated in experimental allergic encephalomyelitis (EAE) rats, were also reduced by TAK-603 administration. These data suggest that TAK-603 acts on the immune system and reduces the number of cells reactive to the relevant antigen.     

汽车用钢连铸坯的高温力学性能

运用经典热模拟的方法研究石钢电炉生产汽车用钢的连铸坯高温力学性能,获得了五个钢种热塑性曲线和强度曲线．针对不同方向铸坯取样的结果与其他研究结果作了对比．运用扫描电镜对试样拉断后的断口形貌进行观察,得出了相应钢在各温度区域的断裂机理．讨论了连铸坯质量与高温力学性能的关系．     

Long-lasting effects of IMHV lesions on social preferences in domestic fowl.

Imprinting leads to strong filial attachment to the mother. Later it influences mate choice. Although nothing is known about the brain regions involved in adult sexual preferences, a particular region of the domestic chick's forebrain (IMHV) has been implicated in filial imprinting. In the present experiment lesions were placed in this region of female chicks soon after hatching. When these and control birds were adult, their sexual preferences were tested. The sham-operated control females had preferences for a male that differed slightly from one with which they had been reared. In contrast, females with lesions did not show a clear preference. It is suggested that the lesion impairs filial and sexual imprinting by disrupting the ability of chicks to learn the characteristics of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Q345钢连铸坯压缩状态下的高温力学性能

Q345钢应用广泛,其在拉伸状态下的高温力学性能已有部分研究,但高温压缩力学性能数据匮乏。利用Gleeble-3500热模拟机对Q345钢连铸坯试样进行了热压缩试验,研究了应变速率为0.01 s-1时试样在压缩状态下的屈服强度、抗压强度和弹性模量等随温度(973~1 673 K)的变化规律,同时探讨了试样在1 473 K时不同应变速率(0.001、0.01和0.05 s-1)下的高温力学性能。结果表明,在973~1 373 K温度内,屈服强度和抗压强度都表现出对温度的敏感性。屈服强度由90降到24 MPa,抗压强度由202降到40 MPa。在1 373~1 673 K温度内,屈服强度和抗压强度降幅都很小。弹性模量随温度的升高而减小,其值在1 473和1 573 K温度下相差最大,达1 712 MPa。屈服强度对应变速率的变化并不敏感,均在20 MPa左右,而极限抗压强度由28增加到45 MPa。最后根据试验数据绘制了Q345钢连铸坯在热压缩状态下的屈服强度等高温性能参数随温度变化的关系曲线,可为轻/重压下等技术提供参考数据。     

High temperature elastic properties of polycrystalline niobium,tantalum, and vanadium

A pulse-echo technique has been used to measure the temperature variation of the velocity of extensional and torsional acoustic waves in polycrystalline Nb(Cb), Ta, and V up to ∼2000 K. The concomitant temperature variation of the elastic moduli do not show any anomalies which would be consistent with a “lattice softening” theory for the departure from linearity of the Arrhenius plots for the diffusivity of interstitial atoms in the Group V metals.     

两种热作模具钢的高温摩擦磨损性能

采用高温摩擦磨损试验机研究了HTCS-130和DAC55两种热作模具钢在100~700℃范围内的耐磨性差异及磨损机制, 并结合X射线衍射仪(XRD)、扫描电子显微镜(SEM)、光学轮廓仪等手段对表面相组成、磨损表面、截面形貌等进行分析. 结果表明: 两种钢的磨损率均在100~700℃范围内呈现先增后减的趋势; 其磨损机制表现为在100℃和300℃分别发生黏着磨损和黏着-轻微氧化磨损; 500℃时磨损机制转变为单一氧化磨损, 磨损表面氧化层由FeO、Fe₂O₃和Fe₃O₄组成, 亚表面发生轻微软化并出现塑性变形层; 700℃时磨损进入严重氧化磨损阶段, 氧化物数量急剧增多, 同时由于马氏体基体回复导致材料出现严重软化, 磨损表面形成连续的氧化层. HTCS-130钢优异的热稳定性能使得基体具有较高硬度和更窄的摩擦软化区, 能够更好地支撑氧化层, 从而在700℃下比DAC55钢更耐磨.      

两种热作模具钢的高温摩擦磨损性能

采用高温摩擦磨损试验机研究了HTCS-130和DAC55两种热作模具钢在100～700℃范围内的耐磨性差异及磨损机制,并结合X射线衍射仪(XRD)、扫描电子显微镜(SEM)、光学轮廓仪等手段对表面相组成、磨损表面、截面形貌等进行分析.结果表明:两种钢的磨损率均在100～700℃范围内呈现先增后减的趋势;其磨损机制表现为在100℃和300℃分别发生黏着磨损和黏着-轻微氧化磨损; 500℃时磨损机制转变为单一氧化磨损,磨损表面氧化层由Fe O、Fe2O3和Fe3O4组成,亚表面发生轻微软化并出现塑性变形层; 700℃时磨损进入严重氧化磨损阶段,氧化物数量急剧增多,同时由于马氏体基体回复导致材料出现严重软化,磨损表面形成连续的氧化层. HTCS-130钢优异的热稳定性能使得基体具有较高硬度和更窄的摩擦软化区,能够更好地支撑氧化层,从而在700℃下比DAC55钢更耐磨.     

High temperature thermodynamic properties of the tungsten carbide WC determined using a galvanic cell technique

The standard free energy of formation of WC has been obtained from emf measurements on the following galvanic cells with BaF₂-BaC₂ solid solutions as the electrolyte: Cr,Cr₂₃C₆ | BaF₂-BaC₂ | W,WC (878 to 1132 K) (A) and Mo,Mo₂C | BaF₂-BaC₂ | W,WC (889 to 1309 K) (B) Combining the results of this study with a previous work¹⁶ and those of Kulkarniet al.,¹⁷ the following equations for ΔG°_f of WC have been determined: from cell (A): ΔG°_f (±950) = -38,000 (±328) -6.6 (±0.3)T joules. From cell (B): ΔG°_f (±1000) = -37,866 (±212) - 6.5 (±0.2)T joules for the reaction W + C = WC.