Deformation mechanisms in commercial TI-5Al-2.5 Sn (0.5 At. pct Oeq) alloy at intermediate and high temperatures (0.3-0.6 tm)

The plastic flow of the commercial α-alloy Ti 5A1-2.5 Sn (0.5 at. pct Oeq) of 11 to 19 μm grain size was investigated in tension over the temperature range of 600 to 117.3 K (CPH structure) and strain rates of 3x10^-5 to 3 per s employing both constant strain rate and strain rate cycling tests. Dynamic strain aging (due to substitutional solutes) occurred in the temperature range of 600 to 850 K (0.31 to 0.44T _m)with an activation energy of 22.5 KcalJmole (94.1 KjJmol) derived from the start of serrations in the stress-strain curves. At temperatures above 850 K (0.46 to 0.60T _m), the deformation could be described by Dorn’s general equation for diffusion controlled mechanisms with an activation energy of 50 KcalJmole (209 KJJmol).     

Deformation mechanisms in commercial Ti (0.5 at. pct oineq) at intermediate and high temperatures (0.3 - 0.6 tinm)

The plastic flow of the commercial titanium material Ti-50A (0.5 at. pct O_eq) of 22 μm grain size was investigated over the temperature range of 600 to 1150 structure) and strain rates of 3 x 10^-5 to 3 x 10^-2 per s employing both constant strain rate and strain rate cycling tests. Dynamic strain aging occurred in the temperature range of 600 to 850 (0.31 to 0.44T_m) with an activation energy of 50 kcal per mole derived from the start of serrations in the stress-strain curves, maxima in strain hardening and minima in ductility. This value is in accord with that for the diffusion of oxygen in titanium. At temperatures above 850 (0.46 to 0.59T_m) the data were very well represented by Weertman’s glide and climb high temperature creep mechanism, giving ε_skT/Dμb= 1.1 x 10⁶ (σ/μ)^4.55 withD = 1.0 x exp (- 57,800/RT). The value of 57.8 kcal per mole is in accord with available self-diffusion data for titanium.     

Deformation kinetics of commercial Ti-50A (0.5 At. Pct Oeq) at low temperatures (T<0.3T m )

The effects of strain rate and temperature on the flow stress of commercial Ti-50A titanium (0.5 at. pct Oeq) wire of 2 and 22 μm grain size were investigated over the range of 4.2 to 700 K. Employing the thermally activated plastic flow concept, it was concluded that the rate-controlling mechanism in Ti-50A at low temperatures (T<≈600 K) is the thermally activated overcoming of interstitial solute atom obstacles (mainly oxygen) by dislocations moving on the first-order prism planes. The Gibbs free energy of activation for the process is ≈1.5 ev(≈0.2 μb³), the maximum force of interaction ≈8 X 10^-5 dynes (≈0.2 smb²), and the activation distance at which the force first rises rapidly ≈ lb. The derived deformation kinetics parameters are in reasonable accord with the Fleischer-Friedel model of solid solution strengthening, the interaction energy being given by the combined effect of the tetragonal distortion and the modulus mismatch produced by the interstitials. Qualitative accord is also obtained for the breaking of chemical bonds between the interstitial solutes and the surrounding titanium atoms by the passage of dislocations.     

Deformation behavior of dilute SnBi(0.5 to 6 at. pct) solid solutions

Tensile and creep tests were conducted to characterize the deformation behavior of four dilute SnBi alloys: SnBi0.5 at. pct, SnBi1.5 at. pct, SnBi3 at. pct, and SnBi6 at. pct, the last two being supersaturated solid solutions at room temperature. The test temperatures were − 20 °C, 23 °C, 90 °C, and 150 °C, and the strain rates ranged from approximately 10⁻⁸ to 10⁻¹ 1/s. In the tensile tests, all the alloys showed strain-hardening behavior up to room temperature. At higher temperatures, only the higher-Bi-content alloys exhibited strain softening. The deformation behavior of the alloys can be divided into two stress regimes, and the change from the low-stress regime to the high-stress regime occurred at around 6 × 10⁻⁴<σ/E<7.5 × 10⁻⁴. The results suggest that, at the low-stress regime, the rate-controlling deformation mechanism changes from dislocation climb to viscous glide with the increasing Bi content of the alloy. At the high-stress regime, the activation energy of deformation is about equal in all the alloys (∼60 kJ/mol) and the stress exponents are high (10<n<12.5). Unlike in the other alloys, bismuth precipitated at room temperature from the solution-annealed and quenched SnBi6 at. pct alloy by the discontinuous mechanism. This strongly affects the mechanical properties and makes the alloy brittle at lower test temperatures. A comparison of the deformation behavior of the dilute SnBi alloys to that of the eutectic SnBi alloy suggests that the deformation of eutectic structure is controlled by the Sn-rich phase containing the equilibrium amount of dissolved Bi.     

Creep mechanism in Fe-1.8 At. Pct Mo alloy at high temperatures

High temperature creep of Fe-1.8Mo alloy, the stress exponent,n, of which is about 4, has been studied to check whether then value can be a good indication of the creep mechanism or not. Creep tests were carried out at 1124 K under 5.9 to 39.2 MPa. After sudden stress increments during the steady-state creep, inverse-type transient creep curves were obtained with no instantaneous permanent strain. Mean internal stresses were determined by stress-transient dip-tests using a back extrapolation technique. The mean internal stress was obviously smaller than the applied stress. These results indicate that creep deformation of Fe-1.8Mo alloy under the present conditions is controlled by the viscous glide motion of dislocations, thoughn is not close to 3. Steady-state creep rates as well as the value ofn calculated from the Orowan-type equation using experimentally obtained values for every parameter, are in reasonable agreement with the observed ones. These findings suggest that classification of creep behavior according to then value is not appropriate in some cases for discussing mechanisms of high temperature creep. Formerly was a Graduate Student, Tohoku University.     

The effect of reversion treatments on precipitation mechanisms in an Al-1.35 at. pct Mg2Si alloy

The effect of reversion treatments on an Al-1.35 at. pct Mg₂Si alloy fully age hardened for 24 h at 160°C was studied by electron microscopy and tension tests. This alloy aged to full strength at 160°C did not show true reversion when heated 15 min at 200 to 300°C. The G.P. zones did not dissolve rapidly at a particular temperature but instead were replaced by the more stable phase, β′ (the intermediate partially coherent form of Mg₂Si). After reheating the fully age hardened alloy 15 min at 250°C, a slight increase in strength was obtained, but the ductility was slightly lowered. Reversion treatments at higher temperatures (275 to 300°C) gradually decreased the strength of the alloy. Two simultaneous reactions are believed to occur during the reversion treatments: 1) the growth of some of the G.P. zones and the dissolution of others and 2) the formation of needles of β′.     

Effects of substitution of Nd in a sand-cast Mg-2.5Nd-0.6Zn-0.5Zr alloy with x wt.% Sm(x=2.5, 4, and 6)

The microstructures and mechanical properties of a series of sand-cast Mg-Sm-Zn-Zr alloys under ascast, solution-treated and peak-aged states were thoroughly investigated. The OM, XRD, SEM and HRTEM were employed to characterize the microstructural evolution. The results indicate that substitution Nd in the conventional Mg-2.5 Nd-0.6 Zn-0.5 Zr alloy with different contents of Sm has comparative grain refinement effect and will fully change the dominant intermetallic phase. In addition, the substituted alloys perform clearly higher strength with comparative ductility at both as-cast and peakaged conditions and much greater aging hardening response than the referential alloy. It is obvious that the strength increments of this alloy are attributed to the changes of the eutectic intermetallic particles on grain boundaries.     

(1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)复合体系的电输运性质及低场磁电阻效应

用固相反应法制备了(1 -x)La0.6Dy0.1Sr0.3MnO3/0.5x( Sb2 O3)系列样品,通过电阻率-温度(ρ-T)曲线以及ρ-T拟合曲线,研究了样品的电输运性质,电输运机制及低场磁电阻效应.结果表明:所有样品在高温区表现为绝缘体导电,在低温区表现为金属导电,产生绝缘体-金属相变;在金属导电区主要是单磁子散射起作用,可以用公式ρ=ρ0+AT拟合;所有样品在整个温区随温度降低MR持续增大,表现出低场磁电阻特征,复合样品的磁电阻(MR)与纯的La0.6Dy0.1Sr0.3 MnO3的MR相比,在低温区减小,在高温区增大,对x=0.15的样品在高温区的MR大幅度提高,当B=0.2 T,T=300 K时,MR达7.79％,比纯La0.6Dy0.1 Sr0.3 MnO3的MR增大2.6倍,有利于MR的实际应用.     

The internal stress in titanium deformed at low temperatures (T<0.33TM)

The internal stressσ _i at 300 K produced by deforming commercial Ti-50A titanium (0.5 at. pct O _eq ) wire of 2 and 22μm grain size to 1 pet strain at temperatures of 78 to 650K was investigated employing the back-extrapolation and decrementai unloading techniques. Concurrent observations of the amount of twinning and the dislocation structure were made by transmission electron microscopy,σ _i by the decrementai unloading method was higher, and was inferred to have a stronger temperature dependence, than that by back-extrapola tion, the difference inσ _i being relatively independent of grain size.σ _i by both methods was found to be relatively independent of the deformation temperature and neither twinning nor dynamic strain aging was found to have a noticeable influence on its value. Since no pro nounced changes in dislocation structure or slip mode were observed for the present material as a function of deformation temperature, the difference inσ _i obtained here between the decremental unloading and the back-extrapolation methods could not be correlated with such changes as was possible by Williamset al. for titanium sheet material of higher in terstitial solute content. M. Doner was formerly affiliated.     

氨气还原氮化五氧化二钒制备V(N,O) 粉体与机理研究

通过氨气还原五氧化二钒（V₂O₅）,在773~873 K下成功地制备V（O, N）粉体.利用X射线衍射（XRD）,场发射扫描电子显微镜（FE-SEM）,热重力分析（TGA）,X射线光电子能谱（XPS）,化学分析和比表面积（BET）等材料表征方法,分析了V₂O₅还原成V（O, N）过程中的物相和形貌演变.根据XRD,XPS和化学分析结果,最终产物应为V（O, N）;钒源的物相转变顺序依次为:V₂O₅→VO₂→V₄O₇→V₂O₃→V（O, N）.另外,还研究了氨还原过程中的形态演变,发现除了VN颗粒看上去似乎是由无数个小的VN晶粒组成外,VN颗粒的尺寸和形状与V₂O₅几乎保持相同.      

m-Chlorophenylpiperazine (mCPP) Modulates the Discriminative Stimulus Effects of Cocaine Through Actions at the 5-HT?C Receptor.

Agonists acting at the serotonin-1B receptor (5-HT?BR) and 5-HT?CR have been reported to potentiate and block, respectively, the discriminative stimulus effects of cocaine. The present investigation reassessed the antagonistic effects of the mixed 5-HT?C/?BR agonist m-chlorophenylpiperazine (mCPP) on the discriminative stimulus effects of cocaine in the presence or absence of selective antagonism of the 5-HT?BR or 5-HT?CR. The stimulus effects of cocaine were attenuated by mCPP at doses that reduced response rates. The selective 5-HT?CR antagonist SB 242084, but not the selective 5-HT?BR antagonist GR 127935, reversed the mCPP-evoked attenuation of the cocaine cue and the suppression of response rates. These results demonstrate that the suppressive effects of mCPP on cocaine discrimination are related to stimulation of the HT?CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of the CaO/SiO2 ratio on the phase equilibria in the ZnO-“Fe2O3”-(PbO + CaO + SiO2) system in air: CaO/SiO2 = 0.1, PbO/(CaO + SiO2) = 6.2, and CaO/SiO2 = 0.6, PbO/(CaO + SiO2) = 4.3

Experimental studies on phase equilibria in the multi-component system PbO-ZnO-CaO-SiO₂-FeO-Fe₂O₃ in air have been conducted to characterize the phase relations of a complex slag system used in the oxidation smelting of lead and in typical lead blast furnace sinters. The liquidus in two pseudoternary sections ZnO-“Fe₂O₃”-(PbO + CaO + SiO₂) with the CaO/SiO₂ weight ratio of 0.1 and the PbO/(CaO + SiO₂) weight ratio of 6.2, and with CaO/SiO₂ weight ratio of 0.6 and the PbO/(CaO + SiO₂) weight ratio of 4.3, have been constructed.     

A search for new 5-HT1A/5-HT2A receptor ligands. In vitro and in vivo studies of 1-[omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-ones

A series of 1-?omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-one derivatives 2-14 was synthesized in order to obtain ligands with a dual 5-HT1A/5-HT2A activity. The majority of those compounds (2-5, 7, 10-13) exhibited a high 5-HT1A (Ki = 2-44 nM) and/or 5-HT2A affinity (Ki = 51 and 39 for 5 and 7, respectively). Induction of lower lip retraction (LLR) and behavioral syndrome and inhibition of these effects evoked by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) were used for determination the agonistic and antagonistic activity, respectively, at 5-HT1A receptors. The 5-HT2A antagonistic activity was assessed by the blocking effect on the head twitches induced by (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in mice. Two of the tested compounds, 1-?3-[4-(3-chlorophenyl)-1-piperazinyl]propyl?-6-fluoroindolin-2(1 H)-one (5) and 1-?3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl?indolin-2(1H)-one (7), demonstrated a high 5-HT1A/5-HT2A affinity and an in vivo antagonistic activity towards both receptor subtypes.     

Cardiac fibroblasts arrest at the G1/S restriction point in response to interleukin (IL)-1beta. Evidence for IL-1beta-induced hypophosphorylation of the retinoblastoma protein

Although responsible for only approximately one-third of the overall myocardial mass, the interstitial fibroblasts of the heart serve a fundamental role in establishing the functional integrity of myocardium and are the major source of myocardial extracellular matrix production. Their importance in clinical medicine is underscored by the observation that fibroblast numbers increase in response to several pathologic circumstances that are associated with an increase in extracellular matrix production, such as long standing hypertension and myocardial injury/infarction. Up to the present time, however, there has been little information available on either the kinetics of the cardiac fibroblast cell cycle, or the fundamental mechanisms that regulate its entry into and exit from the cell cycle. Previous work from our laboratory examining the effects of interleukin (IL)-1beta on myocardial growth and gene expression in culture indicated that cardiac fibroblasts have a diminished capacity to synthesize DNA in response to mitogen in the presence of this cytokine. The mechanism of IL-1beta action was not clear, however, and could have resulted from action at several different points in the cell cycle. The investigations described in this report indicate that IL-1beta exerts its effect on the fibroblast cell cycle at multiple levels through altering the expression of cardiac fibroblast cyclins, cyclin-dependent kinases, and their inhibitors, which ultimately affect the phosphorylation of the retinoblastoma gene product.