Al_(80)Ni_6Y_8Co_4Cu_2 GLASS ALLOYS CONTAINING NANOSCALEPARTICLES BY ISOTHERMAL ANNEALING OR QUENCHING

Al80Ni6 Y8 Co4 Cu2 amorphous ribbons were isothermally annealed and a mixed structure consisting of α-Al particle with a size of less than 15nm and Al3Ni compound with a size of about 30nm was obtained. The crystallization kinetics of Al80Ni6 Y8 Co4 Cu2 amorphous alloy shows that the precipitation of α-Al particles is the growth process controlled by diffusion of the solute elements rejected from the growing crystals. By quenching at different cooling rates, a mixed structure consisting of nanoscale α-Al particles and the remaining glass matrix or structure consisting of nanoscale particle (Al phase or Al3Ni compound) with a size of about 100nm was formed. The addition of Co elements and Cu elements to Al-Ni-Y alloy systems increases the glass formation ability of the alloy and the thermal stability of the supercooled liquid region against crystallization, which results from significant difference of atomic size, strong bonding nature among constituent elements and the low diffisivity of the solute elements due to the concentration gradient in the growing front of crystals.

Thermal stability of Zr_(55)Al_(10)Ni_5Cu_(30)bulk amorphous alloy during continuous heating and isothermal annealing

The crystallization behavior of Zr 55 Al 10 Ni 5Cu 30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order exponential decay relation between the characteristic temperatures and the heating rates during continuous heating process. The activation energy for glass transition E g and that for crystallization E p and E x during continuous heating were evaluated by Kissinger plots. In addition, there is a second order exponential decay relation between the annealing temperature and the corresponding crystallization time during isothermal annealing. The isothermal activation energy obtained by Arrhenius equation increases as crystallization proceeds, indicating the sufficient stability of the residual amorphous structure after initial crystallization.

Study on Multi-stream Heat Exchanger Network Synthesis with Parallel Genetic/Simulated Annealing Algorithm

The multi-stream heat exchanger network synthesis (HENS) problem can be formulated as a mixed integer nonlinear programming model according to Yee et al. Its nonconvexity nature leads to existence of more than one optimum and computational difficulty for traditional algorithms to find the global optimum. Compared with deterministic algorithms, evolutionary computation provides a promising approach to tackle this problem. In this paper, a mathematical model of multi-stream heat exchangers network synthesis problem is setup. Different from the assumption of isothermal mixing of stream splits and thus linearity constraints of Yee et al., non-isothermal mixing is supported. As a consequence, nonlinear constraints are resulted and nonconvexity of the objective function is added. To solve the mathematical model, an algorithm named GA/SA (parallel genetic/simulated annealing algorithm) is detailed for application to the multi-stream heat exchanger network synthesis problem. The performance of the proposed approach is demonstrated with three examples and the obtained solutions indicate the presented approach is effective for multi-stream HENS.

植硅体释光信号特征及其对测年应用的启示

中国西部青藏高原等地区往往缺乏可供AMS^(14)C测年的炭屑、植物残体等物质,开展传统的^(14)C测年有一定难度。然而,这些地区的现代地表常生长着大量草本植物,在其第四纪沉积物中均发现了丰富的植硅体。探索新的植硅体测年技术流程,可为中国西部地区的第四纪沉积物提供新的有效测年途径。植硅体以其自身的广泛分布性、结构稳定性和保存完整性,在测年应用中具有特殊优势,尤其是植硅体碳可用于^(14)C测年。然而,植硅体碳的^(14)C年龄存在高估问题,这可能是由于前处理过程中的快速氧化作用和高温作用破坏了其结构的稳定性和封闭性,需依据其化学组成和某些物理性质变化识别其结构在高温环境下的细微改变。植硅体作为特殊的非晶质含水SiO_(2),其热释光(Thermoluminescence,TL)与光释光(Optically stimulated luminescence,OSL)信号具有测年潜力,可作为直接比对和替代植硅体^(14)C测年法的另一测年手段,同时其释光性质变化可能对识别其物理结构变化具有参考价值。文中以从干稻草中提取的现代植硅体样品为例,对其进行了一系列条件实验,从而确定了植硅体OSL与ITL_(165)信号的具体测试流程,并进行了不同给定剂量的剂量恢复实验,以探讨其剂量-信号的响应关系及测试流程的可行性和可靠性。结果表明,天然植硅体颗粒存在稳定且易晒退的OSL信号,在较高给定剂量(850Gy)的条件下植硅体存在较显著且稳定的_(165)℃TL峰,OSL信号与ITL_(165)信号均有潜力应用于测年研究,但需要已知年龄的样品进行检验。与此同时,不同退火温度加热后的ITL_(500)曲线具有识别植硅体释光性质和物理结构变化的潜力,退火温度升高至300~350℃时植硅体的结构开始发生改变,至约600℃时已发生不可逆的结构改变且逐渐敏化。这也意味着在提取植硅体的过程中应尽可能使用湿式氧化法而非干灰化法,以避免植硅体的结构封闭性遭受破坏,从而造成植硅体碳的AMS^(14)C年龄被高估。

DC53钢连轧棒材退火工艺研究

为了满足DC53材料对加工硬度的特殊需求(硬度≤220 HB),对冷作模具钢DC53热轧材进行了不同退火工艺的试验。结果表明DC53的退火硬度与球化退火的工艺有很大关系,球化退火加热温度850℃、等温温度750℃为最佳退火工艺。在生产中应用该最佳退火工艺后,钢材的硬度均匀,平均硬度HB210左右,金相组织合格,满足用户标准要求。

燃机轮盘锻件热处理工艺

介绍燃机轮盘锻件热处理工艺和产品试制过程,采用正火加等温转变工艺模拟热处理温度场及应力场,设计调质专用辅具,试验结果满足超声波探伤和机械性能要求,证明该工艺的可行性。

无规共聚聚丙烯管材料的微观结构研究

研究了四种无规共聚聚丙烯(PPR)管材料的熔融结晶性能、非等温结晶行为、等规聚丙烯链段分布、结晶形貌,确认了α晶型与γ晶型的存在。结果表明:PPR-1的乙烯含量为4.2wt%,分子量分布(Mw/Mn)为最宽,γ晶型含量为57.6wt%,含有成核剂,结晶较为细密;PPR-2的乙烯含量为3.9wt%,重均分子量(Mw)为最高,γ晶型含量为47.9wt%,含有成核剂,结晶最为细密;PPR-3的乙烯含量为3.6wt%,长等规聚丙烯链段含量最高,γ晶型含量为14.7wt%,不含成核剂;PPR-4的乙烯含量为4.0wt%,γ晶型含量为16.7wt%,不含成核剂。它们具有相近的力学性能;聚丙烯工艺路线、乙烯含量和成核剂等是造成微观结构差异的关键因素。

Single Goss grain growth by isothermal annealing in rolled Fe–Al–Ga–Nb C sheets

The(Fe_(82)Al_(13.5)Ga_(4.5))_(99.9)(NbC)_(0.1) sheets with strong Goss texture and large magnetostriction were prepared by rolling and isothermal annealing processes.Single Goss grain growth was observed in sheets undergoing isothermal annealing at 1050 ℃ for 1 h using Ar as protecting gas.With annealing time increasing to 8 h at1050℃,a largest magnetostriction of 154×10^(-6) is obtained in sheet and a large λ_(//)(the maximum magnetostriction with magnetic field parallel to rolling direction)of 160×10^(-6) along the rolling direction is also observed.The fact that a λ_(//) of 160×10^(-6) along RD can be achieved with only 4.5 at% Ga in the Fe-18 at%(Al,Ga) sheet is of practical importance.Compared with previous studies in Fe-Al and Fe-Ga sheets,this paper provides a more efficient approach to prepare strong Goss textured sheets.In this way,a slow continuous heating process,sulfur-induced surface energy control and high-temperature annealing above 1200 ℃ are no more necessary.It shows a good prospect for industrial production of high-performance magnetostrictive alloy sheets.

Study on precipitation and transition mechanisms from the magnetic properties of silicon steel during annealing

Precipitates play an important role in determining the mechanical and magnetic properties of silicon steel. This paper aims to investigate the growth kinetics of precipitates in commercial silicon steel by analyzing its magnetic properties during isothermal annealing at 200℃. The growth of precipitates was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. In combination with the coercive field and initial susceptibility, this technique offers the advantage of being non-destructive and providing quantitative information about the number, mean radius of precipitates, and fraction of transformation. An ob- served decrease in the number of precipitated particles indicates that the transformation starts from particles of appreciable initial size.

Crystallization behavior of Fe_(78)Si_(13)B_9 metallic glass under high magnetic field

The effects of high magnetic field on the crystallization behavior of the Fe78Si13B9 metallic glass ribbon were studied. The samples were isothermal annealed for 30 min under high magnetic field and no field,respectively. Microstructure transformation during crystallization was identified by X-ray diffraction and transmission electron microscopy. It was found that the crystallizations of Fe78Si13B9 metallic glass processed under different conditions were that the precipitation of dendrite α-Fe（Si） and spherulite （Fe,Si）3B phases forms amorphous matrix and then the metastable （Fe,Si）3B phase transforms into the stable Fe2B phase. The grain size of the crystals is smaller and more homogeneous for the isothermal annealed samples under high magnetic field in comparison with that under no field indicating that the crystallization behavior of Fe78Si13B9 metallic glass is suppressed by high magnetic field.

Adsorption Isotherm, Kinetic and Thermodynamic Modelling of <i>Bacillus subtilis</i>ATCC13952 Mediated Adsorption of Arsenic in Groundwaters of Selected Gold Mining Communities in the Wassa West Municipality of the Western Region of Ghana

This study investigated Bacillus subtilis ATCC13952 as an adsorbent for arsenic in groundwater. Batch experiments were used to determine the effect of contact time, adsorbent dose, arsenic (III) concentration, pH, and temperature on the process. The percentage of arsenic (III) removed was high at a contact time of four days, 3.0 mL of Bacillus subtilis ATCC13952, pH 8 and temperature of 35°C. The kinetics of the process showed the Elovich kinetics model as the best fit for the process. This indicates that arsenic removal was by chemisorption. The analysis of the nonlinear equilibrium isotherms and the error functions showed the Langmuir isotherm as best fit for the process. Mechanistic study of the process indicated bulk diffusion to be the rate-determining step. Thermodynamically, the process was favourable, spontaneous and feasible. When the community water samples were treated with the Bacillus subtilis ATCC13952 at the optimum contact time, adsorbent dose, pH and temperature, 99.96% - 99.97% of arsenic was removed across all sampling points within the studied communities. Hence, the results show that Bacillus subtilis ATCC13952 is an efficient adsorbent for arsenic in aqueous systems and the organism appears to hold the key to purging the environment of arsenic contamination.

Meridional Distributions of Historical Zonal Averages and Their Use to Quantify the Global and Spheroidal Mean Near-Surface Temperature of the Terrestrial Atmosphere

The zonal averages of temperature (the so-called normal temperatures) for numerous parallels of latitude published between 1852 and 1913 by Dove, Forbes, Ferrel, Spitaler, Batchelder, Arrhenius, von Bezold, Hopfner, von Hann, and B&ouml;rnstein were used to quantify the global (spherical) and spheroidal mean near-surface temperature of the terrestrial atmosphere. Only the datasets of Dove and Forbes published in the 1850s provided global averages below 〈T〉=14°C, mainly due to the poor coverage of the Southern Hemisphere by observations during that time. The global averages derived from the distributions of normal temperatures published between 1877 and 1913 ranged from 〈T〉=14.0°C (Batchelder) to 〈T〉=15.1°C (Ferrel). The differences between the global and the spheroidal mean near-surface air temperature are marginal. To examine the uncertainty due to interannual variability and different years considered in the historic zonal mean temperature distributions, the historical normal temperatures were perturbed within ±2σ to obtain ensembles of 50 realizations for each dataset. Numerical integrations of the perturbed distributions indicate uncertainties in the global averages in the range of ±0.3°C to ±0.6°C and depended on the number of available normal temperatures. Compared to our results, the global mean temperature of 〈T〉=15.0°C published by von Hann in 1897 and von Bezold in 1901 and 1906 is notably too high, while 〈T〉=14.4°C published by von Hann in 1908 seems to be more adequate within the range of uncertainty. The HadCRUT4 record provided 〈T〉≌?13.7°C for 1851-1880 and 〈T〉=13.6°C for 1881-1910. The Berkeley record provided 〈T〉=13.6°C and 〈T〉≌?13.5°C for these periods, respectively. The NASA GISS record yielded 〈T〉=13.6°C for 1881-1910 as well. These results are notably lower than those based on the historic zonal means. For 1991-2018, the HadCRUT4, Berkeley, and NASA GISS records provided 〈T〉=14.4°C, 〈T〉=14.5°C, and 〈T〉=14.5°C, respectively. The comparison of the 1991-2018 globally averaged near-surface temperature with those derived from distributions of zonal temperature averages for numerous parallels of latitude suggests no change for the past 100 years.

Cooling Rate Dependence of Structural Order and Energy Landscape in Zr_(55)Cu_(35)Al_(10) Glass

Classical molecular dynamics simulation has been widely used to study the rapid cooling process of preparing amorphous alloys.However,the simulated cooling rate is several orders of magnitude higher than the experimental cooling rate.In this paper,Zr_(55)Cu_(35)Al_(10)alloy was taken as an example.It is found that adding isothermal annealing at a temperature slightly lower than Tand prolonging isothermal annealing time could effectively reduce the cooling rate.The glassy sample prepared in this way demonstrates significant energetic stability and well-developed short-range and medium-range order.

Composition design and properties of CoNbZr amorphous films deposited by unbalanced magnetron sputtering

Co87Nb10Zr3,Co76Nb19Zr5,Co64Nb26Zr10 and Co64Nb16Zr20 amorphous films were deposited on noncrystalline glass substrates by DC unbalanced magnetron sputtering. The compositions of amorphous films were tailored in the light of the individual deposition rate of Co,Nb and Zr. The amorphous films with the anticipated composition were prepared by means of co-sputtering Co,Nb and Zr targets simultaneously. It is indicated that there is interaction among three targets during co-sputtering. The morphology and composition of the films were observed by SEM,AFM and EDS. The structure and magnetic property were measured by XRD and physical property measurement system(PPMS) . The coercivity changes with the composition,varying from 240 to 1 600 A/m. After vacuum isothermal annealing at temperatures of 475,500,525 and 550 ℃ for 15 and 30 min,respectively,it is found that high Nb content is beneficial to improving thermal stability of amorphous films. The crystallized films have the mean grain size of 2-19 nm.

Crystallization Behavior and Magnetic Properties of(Fe0.6Co0.4)86Hf7B6Cu1 Alloy

Feo.eCoo.^seHfTBsCu! nanocrystalline alloy obtained in isothermal annealing process from amorphous precursor was investigated as candidate of soft magnetic materials for high temperature applications. Co substitution for Fe can enhance the curie temperature of amorphous alloy (Tc = 630 °C) and improve the magnetization of nanocrystalline alloy at high temperature ( = 1.56T at 550 °C). After annealing amorphous precursor at 550 °C for 1 hour, the optimum nanocrystalline alloy can be obtained which shows the local minimum coercivity ( = 16 A/m). The coercivity increases with the increase of annealing temperature corresponding to the formation of ferromagnetic phase in the secondary crystallization. Furthermore, additions of Hf and B elements reduce the melting temperature of the alloy studied comparing with the Fe-Co binary alloy.

Crystallization behavior of amorphous Zr_(70)Cu_(20)Ni_(10) alloy annealed at 380 ℃

Crystallization behavior of amorphous Zr 70 Cu 20 Ni 10 alloy isothermally annealed at 380 ℃ was first investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It has been found that an exothermic peak appears in the DSC trace when the annealing time is about 17～18 min, indicating a certain phase transformation occurs in the matrix of amorphous Zr 70 Cu 20 Ni 10 alloy. Meanwhile, isothermal annealing experiments for amorphous Zr 70 Cu 20 Ni 10 alloy ranging from 360 ℃ to 400 ℃ with a temperature interval of 10 ℃ were also carried out, from which no exothermic reaction can be observed except for the case of 380 ℃. This behavior indicates that the phase transformation during isothermal annealing of amorphous Zr 70 Cu 20 Ni 10 alloy is strongly temperature and time dependent. Further investigations are required to reveal the nature of such phenomenon.

高强韧珠光体球墨铸铁的研究

在球墨铸铁成分优化基础上,用万能材料试验机、布氏硬度计和金相分析显微镜研究了球墨铸铁经多元合金化、型内孕育处理和等温正火后的组织和和性能。结果表明:经Cu、Mo、Sb多元合金化和型内孕育处理的球墨铸铁,其铸态和等温正火处理后的组织明显改善,共晶团数目增加,基体组织细化,石墨球形态圆整、细小,珠光体数量增多,比例均大于90%,力学性能显著提高。与未合金化的球墨铸铁比,Cu,Mo,Sb多元合金化的球墨铸铁,其铸态和等温正火处理后的屈服强度R_(0.2)、抗拉强度R_(m)和硬度HB分别提高了25%、20%,47%、17%,41%、11%,达到502、620 MPa,811、975 MPa,256HB、298HB,伸长率A均大于6%。

汽车齿轮锻坯热处理工艺优化研究

为了进一步提高汽车齿轮的质量,采用多种热处理工艺对齿轮锻坯进行热处理,有利于减低汽车齿轮锻坯在渗碳淬火时发生不规则变形的概率。为获取热处理工艺对汽车齿轮锻坯性能的影响,利用等温退火工艺和常规退火工艺验证汽车齿轮的性能。结果表明,等温退火工艺更适用于汽车齿轮的生产制造,可使汽车齿轮的耐磨损性能出现明显提升,有利于提高汽车齿轮的整体质量。

等温退火温度对薄规格取向硅钢二次再结晶行为的影响

采用高温等温退火方式,研究了0.20 mm厚薄规格取向硅钢在不同等温温度及不同升温速率下的二次再结晶行为差异,测出二次再结晶百分数、基体晶粒尺寸及取向变化,以及二次再结晶晶粒取向偏差度与尺寸的关系。结果表明,提高升温速率会推迟二次再结晶开始时间和二次再结晶完成时间;提高等温退火温度,可促进抑制剂熟化并加速二次再结晶的完成;{114}〈481〉取向基体晶粒对二次再结晶晶粒的长大有较大的阻碍作用;较低的升温速率和较低的二次再结晶温度(1030℃)有利于锋锐的高斯织构的形成,此时二次晶粒尺寸与高斯取向偏差度有良好的对应关系。