强碳化物形成元素与碳的配比关系和稳定化处理对310S奥氏体不锈钢析出相行为的影响

高Cr/Ni含量的奥氏体不锈钢由于具有优异的综合性能而有望被用作超临界水冷堆的燃料包壳材料,但是该类奥氏体不锈钢存在组织稳定性差的问题,即在873~1123K温度下长期时效后晶界上会析出大量的Cr23C6和σ相,从而导致材料的脆化和晶间腐蚀。为了提高该类不锈钢的高温组织稳定性,本工作系统研究了强碳化物形成元素M(M=Nb、Ti、Ta和Zr)与C的配比关系以及稳定化处理工艺对310S高温下析出相行为的影响。设计合金采用铜模快冷技术吸铸成直径为6mm的棒材,并对其进行1473K/0.5h固溶处理、1173K/0.5h稳定化处理(部分样品)、1073K/24h时效处理。分别采用OM、SEM-EDS、EPMA和TEM等手段对合金不同热处理状态的析出相进行表征。研究结果表明,M的加入均能促进MC粒子的析出,促进效果为Ta>Nb/Ti>Zr,且M与C的最佳比例关系为1/1(原子比);当M与C的原子比为2/1时会促进脆性相σ析出,而当M与C的原子比为1/1时,1073K/24h时效后晶界上只有Cr23C6析出。稳定化处理能使MC优先析出,可减少时效过程中粗大Cr23C6的析出量。本工作为超临界水冷堆燃料包壳材料的开发提供了有效的基础数据支撑,并为下一步的工作指明了方向。

强碳化物形成元素对铸造高强钢低温性能的影响

研究了微量强碳化物形成元素V、Nb和Ti对超低温用Cr-Ni-Co-Mo马氏体时效不锈钢强度和超低温冲击韧性的影响,结果表明,加入0.03%的Ti能够细化铸态组织,从而提高材料的力学性能;而加入0.08%V或0.03%Nb对钢的组织并无较大影响,对试验材料的力学性能的提高无作用。

胎体中强碳化物形成元素对金刚石工具质量的影响

在胎体中,金刚石原料的质量固然对其性能及质量有重要影响,而强碳化物形成元素在胎体中所扮演的是金刚石与胎体中其它材料之间桥梁的作用。如果它的作用不强,即使提高金刚石的品级及质量,对整个胎体质量的提高也是事倍功半。因此,我们对强碳化物形成元素在胎体中的作用及对金刚石工具质量的影响应有所研究。 一、纯金属元素对金刚石的浸润

钒对金刚石工具新型铜基结合剂组织和性能的影响

通过抗弯强度测试、显微硬度和扫描电镜研究新型铜基结合剂CSF中添加V元素后组织和性能的影响.结果表明:强碳化物形成元素V可与金刚石发生界面反应,富集于金刚石表面,当V质量分数低于4%时,可通过固溶强化显著提升胎体的硬度以及胎体对金刚石的把持力,且把持力随着V的增加而增加;当V质量分数超过4%时,胎体组织不均匀,性能降低,对金刚石的把持力下降.

金刚石表面金属化在金刚石钻头制造中的应用研究

通过先对金刚石进行预处理，之后采用化学镀方法镀一层Ni-W-P合金膜，再采用电镀方法，镀一层Fe－W合金或Cr金属膜。镀覆合金膜的金刚石经过热压烧结工艺过程，合金膜能同金刚石实现强碳化物冶金结合，能同股体金属生成高性能的合金体，实现牢固的包镶，达到提高金刚石钻头使用寿命的目的。

浅论金工课程特点及其教学方法

作为机械制造专业的必修课——金属工艺学,有哪些特点?针对这些特点,采用哪些教学方法,才能提高这门课的教学效果呢?下面笔者结合教学实践,作些初探.

Comparative Bioremediation of Petroleum Hydrocarbon-Contaminated Soil by Biostimulation, Bioaugmentation and Surfactant Addition

A bench-scale biopiling experiment was conducted to hydrocarbon bioremediation in a chronically contaminated soil compare the ability of different techniques to enhance petroleum After 195 days, 10%-32% removal of TPHs （total petroleum hydrocarbons） occurred in unamended soil （control）. Biostimulation by inorganic nutrient addition enhanced TPH removal （49%） confirming that bioremediation was nutrient limited and the soil contained a well-adapted hydrocarbonoclastic microbial community. The addition of organic amendments including green waste at 25% and 50% （w/w） and a commercial product called DaramendTM had a further biostimulatory effect （50%-66%, 34%-59% and 69%-80% TPH removal respectively）. Bioaugmentation using two commercially available petroleum hydrocarbon degrading microbial cultures with nutrients enhanced TPH removal in the case of RemActivTM （60%-69%）, but had a marginal effect using Recycler 102 （49%-55%）. The effect of a non-ionic surfactant in green waste amended soil was variable （52%-72% TPH reduction）, but its potential to enhance biodegradation presumably by promoting contaminant bioavailability was demonstrated. High degradation of artificially added polycyclic aromatic hydrocarbons （PAHs） occurred after 106 days （75%-84%）, but significant differences between the control and treatments were unapparent, suggesting that spiked soils do not reflect the behavior of contaminants in genuinely polluted and weathered soil.

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al2O3 filler （Cr（a-Al2O3）/geopolymer composites） were fabricated, and the effects of heat treatment temperatures up to 1 200 ℃ on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature （25 ℃ ） to 1000 ℃. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000℃, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 ℃ as the hydration water of geopolymer matrix is lost. The addition of α-Al2O3 particle filler into the composites clearly increases the onset crystalline temperature of leucite （KAlSi2O6） from the amorphous geopolymer matrix. In addition, the addition of α-Al2O3 particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.

Electrical resistance stability of high content carbon fiber reinforced cement composite

The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

Effects of welding parameters and tool geometry on properties of 3003-H18 aluminum alloy to mild steel friction stir weld

Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding （FSW）. A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor （HIF） achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2-0.4, by TMAZ at HIF of 0.4-0.8 and by intermetallics and/or defects at HIF0.8.

钛锆对激光熔覆原位合成颗粒增强铁基复合涂层组织的影响

运用激光熔覆的方法在中碳钢表面原位合成制备了颗粒增强铁基复合涂层。通过调整两种强碳化物形成元素Ti和Zr的相对含量,研究了不同配比下原位自生碳化物颗粒相的分布特征。结果表明,在总量一定的情况下,复合添加Ti和Zr可以提高颗粒分布密度和颗粒相面积比。其中,以Ti和Zr的质量比为1:1时得到的颗粒密度最大、颗粒尺寸分布最均匀。同时对不同的颗粒分布状态下涂层的显微硬度进行了研究。

An Innovative Process to Improve Turbidity and Organics Removal by BAC Filters

The turbidity criterion for the product water of a WTP according to the State Project ‘863’ on the safeguard technology of drinking water in the southern areas of China is 0.1 NTU. The turbidity removal in the activated carbon filter was analyzed in a pilot-scale test and an innovative technology to improve the turbidity removal in a biologically activated carbon (BAC) filter was put forward in order to meet the criterion. Experimental results showed that the enhanced filtration by adding polymerized aluminium chloride (PAC) into the BAC filter was quite effective in turbidity control. The effluent turbidity was kept at a stable level (mean) of 0.033 NTU with a high removal of about 80% for influent turbidity of 0.110-0.240 NTU with an addition of PAC at 0.05 mg L -1, meeting the requirement for filtrate turbidity equal to or less than 0.1NTUC totally. In addition, the larger the PAC dosage was, the lower the effluent turbidity was. However, further improvement of turbidity removal was not obvious for PAC dosages beyond 0.10 mg L -1, and an optimal PAC dosage in the range of 0.]05-0.10 mg L -1 was proposed.

Enhanced Performance of Denitrifying Sulfide Removal Process by 1,2-Naphthoquinone-4-Sulphonate

The denitrifying sulfide removal(DSR) process with bio-granules comprising both heterotrophic and autotrophic denitrifiers can simultaneously convert nitrate, sulfide and acetate species into di-nitrogen gas, elemental sulfur and carbon dioxide, respectively, at high loading rates. This study has determined that the reaction rate of sulfide oxidized into sulfur could be enhanced in the presence of 1,2-naphthoquinone-4-sulphonate(NQS). The presence of NQS mitigated the inhibition effects of sulfide species on denitrification. Furthermore, the reaction rates of nitrate and acetate to nitrogen gas and CO_2, respectively, were also promoted in the presence of NQS, thereby enhancing the performance of DSR granules. The advantages and disadvantages of applying the NQS-DSR process are discussed.

Ni-Cr钎料钎焊金刚石界面强化的第一性原理计算与试验研究

采用第一性原理计算方法,系统研究强碳化物形成元素X(X=Mn、Ti、V、Zr、Nb、Mo、Hf、Ta、W)掺杂的Ni-Cr钎料钎焊金刚石界面微观作用行为及机理,并通过钎焊金刚石试验对计算结果进行验证。嵌入能、界面分离功及界面能的计算结果表明,强碳化物形成元素X均倾向于在Ni-Cr钎料与金刚石的界面处偏析,并且不同程度地增强Ni-Cr钎料与金刚石的界面结合强度与稳定性,其中,Hf、Ta、Zr、Nb、W的强化效果尤为明显;电子结构分析表明,强碳化物形成元素X的掺杂可促进Ni-Cr钎料中的Cr原子与金刚石中的C原子成键,有效改善Ni-Cr钎料对金刚石的润湿性,同时还削弱Ni元素对金刚石石墨化的催化作用。基于Nb掺杂Ni-Cr钎料的钎焊金刚石试验表明,Nb掺杂使得Ni-Cr钎料对金刚石的爬升效果更为明显,界面冶金反应更为充分,金刚石表面生成Cr3C2和Cr7C3两种碳化物,界面得到有效强化;同时,Nb掺杂还明显削弱Ni元素对金刚石的石墨化催化作用,进而提高钎焊金刚石试件的加工性能,很好地验证理论计算结果。研究工作为基于材料基因组理念的钎焊金刚石钎料设计开发提供理论依据与参考。

Improvement of the CFRP Mechanical Properties Using Taguchi Method to Optimize the Formation Conditions

Carbon fiber composites have high strength, high stiffness and light weight characteristics to apply to many fields, such as leisure, energy and transportation industries. The CFRP （carbon fiber reinforced polymers/plastics） composites made of carbon fibers as reinforcement and epoxy resins as matrix were prepared by drum winding process. Various parameters such as molding temperature, molding pressure and pressing time were selected as the pre-pregs were laminated to be the CFRP. The effects of fabricating parameters which affected the mechanical properties of CFRPs were analyzed by Taguchi method in this study. The results showed that molding temperature was the main factor to influence the mechanical properties of composites.

Improvement of Impact Absorbed Energy of CFRPs on Adding the Nanoparticles into Epoxy Resins

The present study investigates the effect of the addition of nanoparticles into epoxy resins as the matrix on the impact absorbed energy of CFRP （carbon fiber reinforced polymer）. Impact absorbed energy is one of the main properties to evaluate the CFRP＇s performance for transportation and aerospace structures. Two types of nanoparticle, namely nanofibers and nano-silica beads, were added into the epoxy resin to improve the impact absorption capacity of the CFRP. Two modified additives and conventional epoxy resins were quantitatively compared. The impact test results showed that impact absorbed energy for nanofibers was higher than nano-silica beads, and nanofibers as the additive promoted about 11% of impact absorbed energy compared with neat epoxy resin.

Cassava stillage and its anaerobic fermentation liquid as external carbon sources in biological nutrient removal

The aim of this study was to investigate the effects of one kind of food industry effluent, cassava stillage and its anaerobic fermentation liquid, on biological nutrient removal （BNR） from municipal wastewater in anaerobic- anoxic-aerobic sequencing batch reactors （SBRs）. Experiments were carried out with cassava stillage supernatant and its anaerobic fermentation liquid, and one pure compound （sodium acetate） served as an external carbon source. Cyclic studies indicated that the cassava by-products not only affected the transformation of nitrogen, phosphorus, poly-13-hydroxyalkanoates （PHAs）, and glycogen in the BNR process, but also resulted in higher removal efficiencies for phosphorus and nitrogen compared with sodium acetate. Furthermore, assays for phosphorus accumulating or- ganisms （PAOs） and denitrifying phosphorus accumulating organisms （DPAOs） demonstrated that the proportion of DPAOs to PAOs reached 62.6% （Day 86） and 61.8% （Day 65） when using cassava stillage and its anaerobic fer- mentation liquid, respectively, as the external carbon source. In addition, the nitrate utilization rates （NURs） of the cassava by-products were in the range of 5.49-5.99 g N/（kg MLVSS.h） （MLVSS is mixed liquor volatile suspended solids） and 6.63-6.81 g N/（kg MLVSS.h）, respectively. The improvement in BNR performance and the reduction in the amount of cassava stillage to be treated in-situ make cassava stillage and its anaerobic fermentation liquid attractive alternatives to sodium acetate as external carbon sources for BNR processes.

Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes

The effects of two different external carbon sources （acetate and ethanol） and electron acceptors （dissolved oxygen, nitrate, and nitrite） were investigated under aerobic and anoxic conditions with non-acclimated process bi- omass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/（g MLVSS.h） （MLVSS： mixed liquor volatile suspended solids）, respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO2-N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher deni- trification rates were obtained with acetate （1.4 and 0.8 mg N/（g MLVSS.h）） compared to ethanol （1.1 and 0.7 mg N/ （g MLVSS.h）） for both anoxic electron acceptors （nitrate and nitrite）.

Comparative Analysis of Some Representative Models of Viscosity Versus Pressure in the Case of Various Hydrocarbons and Their Mixtures

A critical study of some representative models has been conducted with the experimental determinations of the viscosity of ten pure substances and three binary systems measured as a function of temperature T(25℃,40℃,60℃,80℃,90℃)and pressure P(≤ 100 MPa). The pure substances were:toluene,p-xylene,m-xylene,o-xylene,methylcyclohexane, methylnaphtalene,decahydronaphtalene,phenyldodecane,heptamethylnonane and tetramethylpentadecane(pristane).The three binaries were:toluene+ tetramethylpentadecane,toluene+ methylnaphtalene and toluene+ heptamethylnonane,for molar fractions x of toluene ranging between 0 and 1.The three binaries are highly'contrasted' systems,i.e.systems in which the viscosities of the pure components are very different for each P,T pair.In all,547 experimental determinations were carried out,the 279 experimental data for viscosity of the pure substances and 268 data concerning the mixtures(x ≠0 and 1) were used to make a critical analysis of the various representative models,These included an empirical representation of variations of versus T on each isobar,a self-referencing model developed in our laboratory,a corresponding states model with one reference,various mixing rules with or without adjustable parameters,a combination of the self-referencing model and mixing rules,a method based on the Bloomfield and Dewan excess viscosity,and a group contribution method,comparison of the results showed the self-referencing method to be of particular interest,Moreover when coupled with mixing rules without adjustable parameters it was able to account satisfactorily for the variationsη(P,T,x) of the mixtures,on the simple basis of knowledge if the viscosity of the components of the system,at 25℃ and at atmospheric pressure,For all the binaries an average absolute deviation of 9.5% was observed.Finally it appears that the introduction of the pressure parameter does not alter the usual performance of each of the models tested,although they were not al equivalent as regard their performances.