富氮含能晶体4-氨基-3,7-二硝基三唑-[5,1,c][1,2,4]三嗪高压行为的密度泛函研究（英文）

采用周期性密度泛函理论(DFT)的GGA/PBE-G06方法研究了富氮含能晶体4-氨基-3,7-二硝基三唑-[5,1,c][1,2,4]三嗪(DPX-26)在静水压0~130 GPa范围内的高压行为。通过计算晶格参数(a、b、c)、键长、带隙(ΔE g)和态密度(DOS),分析了DPX-26的晶体结构、分子结构和电子结构随压力的变化情况。结果表明,DPX-26晶体在81、82和92 GPa发生3次显著的结构转变。81 GPa时,分子间六元环破裂;在82 GPa,C4—N7键拉长,三唑环严重扭曲并解离,N4—H6键拉长至0.150 7 nm,共价作用转变为氢键作用;92 GPa时,C4—N7键键长从0.232 4 nm减小至0.133 3 nm,三唑环再次形成。压力增加导致体系离域性增强。

不同应变率加载下硅的高压相变行为

高压相变是凝聚态物理、地球与行星科学、材料科学等领域关注的核心问题之一,而加载应变率是相变动力学过程的重要影响因素。由于动态加载下物质相结构原位诊断技术的不足以及宽广加载应变率下物质高压相变系统实验研究的缺失,难以开展基于原子尺度物理机制的相变动力学过程建模和数值模拟研究。由于硅的高压相极其丰富,且拥有大量亚稳相,动力学因素在其高压相变过程中发挥着至关重要的作用,因此,硅是研究高压相变动力学的理想材料,对普适相变动力学过程的理论建模具有重要意义。以硅为例,介绍其在准静态、中等应变率和高应变率加载下的相变行为,探讨加载应变率对其高压相变行为的影响。

氮-烃体系高压相态行为的研究

对 1 7个含氮二元体系的高压汽液平衡数据 ,按 4个状态方程 (SRK、 PR、 PT和 YL)关联了二元交互作用参数值 ,并对 PT方程建立了关联式。基于二元体系的关联结果 ,对 1 9个三元至十元含氮体系的泡点压力和液相密度进行了预测计算 ,结果表明

结晶性芳香聚酯高压结晶行为研究进展

运用高压极限手段研究聚合物的结构、形态和性能是 2 0世纪 6 0年代以来兴起的一项聚合物前沿课题。本文主要结合作者自己的研究工作 ,重点叙述聚对苯二甲酸乙二醇酯 (PET)的高压结晶行为研究 ,包括温度、压力、时间及分子量对PET高压结晶行为的影响 ,高压结晶PET的形态 ,以及对PET伸直链晶体结晶机理的探讨 ,同时简要介绍了对其它结晶性芳香聚酯诸如聚对苯二甲酸丁二醇酯 (PBT)及聚对萘二甲酸乙二醇酯 (PEN)的高压结晶行为研究 ,反映了该领域的研究概况和最新进展 ,并对今后的研究提出了展望。

镍基690合金在超纯水中常温下的电化学行为及高温高压下的腐蚀行为

目前,国内对镍基690合金在超纯水中的腐蚀行为报道不多。利用动电位极化和电化学阻抗法研究了镍基690合金在常温超纯水中的电化学行为;利用扫描电镜、能谱和X射线衍射等方法研究了镍基690合金在高温高压超纯水中的腐蚀行为。结果表明:镍基690合金在纯水中常温下具有较小的腐蚀电流密度和较大的阻抗,耐蚀性较好;镍基690合金在高温高压超纯水中浸泡4 400 h后,表面仅产生轻微腐蚀,腐蚀产物由双层钝化膜结构组成,外层富Ni内层富Cr,可有效抑制腐蚀反应的进一步发生,从而表现出优良的耐蚀性能。

方管短玻璃纤维增强聚丙烯高压水穿透行为研究

采用方形截面管件,以短玻璃纤维增强聚丙烯为原料,通过溢流法水辅助注射成型实验探究了熔体注射温度、注水延迟时间和注水压力等工艺参数对制件宏观现象的影响机理,并分析了高压水在方形管道中的穿透行为。结果表明,当熔体温度升高时,方管的直角边和斜边残余壁厚都呈减小趋势,但温度过高时会出现管件收缩现象,管件截面中空面积增大且截面形状与高压水的穿透前沿形状一致,偏圆形,但截面的圆率逐渐减小;当注水压力增加时,管件残余壁厚减小,截面中空面积增大,其截面形状随着注水压力的增加逐渐与型腔结构一致,偏方形;当注水延迟时间增加时,管件残余壁厚增大,中空截面减小且管件截面形状也与高压水前穿透前沿一致,偏圆形,但相较另外两个参数,注水延迟时间对方管件的影响程度更小,因而对截面的圆率影响不大。

《高温高压氢环境下石化用钢开裂行为及超声检测研究》通过中石化总公司技术鉴定

由抚顺石油学院化工机械系承担的应用基础项目“高温高压氢环境下石化用钢开裂行为及超声波检测研究”通过总公司发展部组织的鉴定．项目组由谢根桂为负责人，李晓刚为执行负责人．中科院金属腐蚀与防护所柯伟．姚治铭为技术指导，

离子液体-超临界二氧化碳两相体系研究进展

简要介绍了离子液体-二氧化碳(IL-CO2)两相体系及IL面临的挑战。综述了利用CO2从ILs回收溶质、从有机溶剂中分离IL、IL-CO2体系的高压相行为I、Ls在CO2相的溶度和IL-SCCO2体系分子水平的交互作用几个方面,讨论了压力、温度、阴离子的性质和阳离子烷基链长度对CO2溶度的影响,对尚存在的问题提出了建议,并对两相体系的发展方向进行了展望。

Flow behavior and microstructure of ZK60 magnesium alloy compressed at high strain rate

Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

Deformation behavior and microstructural evolution of Al-Zn-Cu-Mg-Sc-Zr alloy during high temperature compression

The deformation behavior of a new Al-Zn-Cu-Mg-Sc-Zr alloy was investigated with compression tests in temperature range of 380?470 ℃ and strain rate range of 0.001-10 s-1 using Gleeble 1500 system, and the associated microstructural evolutions were studied by metallographic microscopy and transmission electron microscopy. The results show that true stress—strain curves exhibit a peak stress, followed by a dynamic flow softening at low strains (ε<0.05). The stress decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon exponential equation with the activation energy for deformation of 157.9 kJ/mol. The substructure in the deformed specimens consists of few fine precipitates with equaixed polygonized subgrains in the elongated grains and developed serrations at the grain boundaries. The dynamic flow softening is attributed mainly to dynamic recovery and dynamic recrystallization.

Sorption and Diffusion Behavior of Carbon Dioxide into Poly（l-lactic acid） Films at Elevated Pressures

Equilibrium sorption amount, desorption diffusion coefficients and sorption diffusion coefficients of CO2 in poly（l-lactic acid） （PLLA） films at elevated pressures were determined by the gravimetric method, in which the Fick＇s diffusion model was applied to analyze both the desorption and sorption processes. The equilibrium sorption amount of CO2 in PLLA increased with lowering temperature and elevating pressure at the temperature range from 40 to 60 ℃ and pressure from 10^4 to 2x10^4 kPa. Desorption diffusion coefficients were greatly influenced by the equilibrium sorption amount, and they were in the same order of magnitude as the sorption diffusion coefficients. The scan electron microscope （SEM） photos demonstrated that there was no foaming phenomenon of the PLLA film during desorption and sorption processes. The XRD spectra implied that the crystalline degree of PLLA film decreased after CO2 processing. It was concluded that PLLA polymer could be well swollen and plasticized by supercritical CO2.

High temperature tensile behaviors of extruded and rolled AZ31 Mg alloy

High temperature tensile ductilities and deformation mechanisms of an extruded and rolled AZ31 Mg alloy were investigated.Elongation-to-failure tests were conducted under constant T-head velocity and constant temperatures ranging from 300℃ to 450℃.Strain-rate-change tests were conducted under varying strain rate from 5×10-5s-1to 2×10-2s-1and constant temperature from 300℃ to 450℃.Experimental results show that the maximum elongation of the AZ31 alloy with an average grain size of about 19μm is 117%at strain rate of 10- 3s-1 and temperature of 450℃.Stress exponent and activation energy were characterized to clarify the deformation mechanisms.The enhanced ductility is dominated by solute drag dislocation creep,and the major failure mechanism is cavity growth and interlinkage.

Coarsening Behavior ofγ′Precipitates and Compression Performance of Novel Co-Ni-Al-W Superalloy

The coarsening behavior ofγʹprecipitate phase at different temperatures and the compressive performance of novel Co-Ni-Al-W superalloy were investigated.Experiment results show that the evolution of the mean radius and volume fraction of theγʹphase obeys the classical Lifshitz-Slyozov-Wagner model.The coarsening rate of theγʹphase exhibits a significant dependence on the aging temperature,which increases from 1.30×10^(−27)m^(3)/s at 800℃to 9.56×10−27 m^(3)/s at 900℃.The activation energy ofγʹphase is mainly influenced by the W diffusion in theγmatrix,presenting as 210 kJ/mol.The prepared Co-Ni-Al-W alloy possesses superb comprehensive properties,particularly the good combination of highγʹsolvus temperature(1221℃)and low density(8.7 g/cm^(3)).Besides,the compressive yield strength of the Co-Ni-Al-W alloy at ambient and high temperatures are higher than that of otherγʹ-strengthened Co-based superalloys.The compressive yield strength of the Co-Ni-Al-W alloy at 850℃is as high as 774 MPa.

Low strain rate compressive behavior of high porosity closed-cell aluminum foams

The impact of a rigid body(protected structure) together with cushion material(cellular metal foam) on hard ground from a fixed height was investigated.An analytical one-degree-of-freedom colliding model(ODF-CM) was established to analyze the protection ability and energy absorption by the foam under low velocity impact conditions.For validation,drop hammer experiments were carried out for high porosity closed-cell aluminum foam specimens subjected to low velocity impact loading.The dynamic deformation behavior of the specimen was observed and the velocity attenuation of the drop hammer was measured.The results demonstrated that the aluminum foam had excellent energy absorption capabilities,with its dynamic compressive behavior similar to that obtained under quasi-static loading conditions.Finite element method(FEM) was subsequently employed to obtain stress distributions in the foam specimen.As the propagating period of stress in the specimen was far less than the duration of attenuation,the evolution of the stress was similar to that under quasi-static loading conditions and no obvious stress wave effect was observed,which agreed with the experimental observation.Finally,the predicted velocity attenuation by the ODF-CM was compared with both the experimental measurements and FEM simulation,and good agreements were achieved when the stress distribution was considered to be uniform and the "quasi-static" compressive properties are employed.

Experimental study on mechanical behaviors of pseudo-ductile cementitious composites under biaxial compression

Experimental investigation was conducted to characterize the responses of pseudo-ductile cementitious composites (PDCCs) when subjected to uniaxial and biaxial compression.The PDCCs is a class of fiber reinforced cementitious composites with ultra-high ductility by using a low volume fraction (2%) of polyvinyl alcohol (PVA) fiber.Two different strength grades of PDCC were examined with cubic specimen size of 100 mm in the tests.The specimens were loaded with a servo-hydraulic jack at different stress ratios.The principle stresses and strains of the specimens were recorded,and the failure modes with various stress states were examined.The test results indicated that the ultimate strength of PDCCs increased due to the lateral confinement in the other principal stress direction,and the maximum ultimate strength occurred at the biaxial stress ratio of 0.25,which was very different from common concrete material.For the PDCC specimens,the biaxial strength may be lower than the uniaxial strength when subjected to biaxial compression with the stress ratio of 1.0,and the failure mode showed a shear-type failure because of the bridging effect of fibers.Finally,a failure criterion was proposed for PDCCs under biaxial compression.

Investigation on Temperature Separation and Flow Behaviour in Vortex Chamber

In the previous researches, it is known that the swirl flow in circular pipe causes the temperature separation. Recently, it is shown that the temperature separation occurs in a vortex chamber when compressed air are pumped into this device from the periphery. Especially, in a cavity installed in the periphery of the chamber, the highest temperature was observed. Therefore, it is expected that this device can be used as a heat source in the engineering field. In recent researches, the mechanism of temperature separation in vortex chamber has been investigated by some researchers. However, there are few researches for the effect of diameter and volume of vortex chamber, height of central rod and position of cavity on the temperature separation. Further, no detailed physical explanation has been made for the temperature separation phenomena in the vortex chamber. In the present study, the effects of chamber configuration and position of the cavity on temperature separation in the vortex chamber were investigated experimentally.

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