石墨烯/钛基复合材料的界面反应控制、微观组织和压缩性能

将Ti6Al4V（TC4）粉末与少层石墨烯（GR）粉末进行三维机械旋转混合,实现了GR在TC4球形粉末表面的均匀包覆,经放电等离子烧结(SPS)得到增强相呈三维网络状分布的GR/TC4复合材料。对不同的SPS烧结温度、保温时间、升温速率和轴向压力对GR与钛基体原位界面反应程度的影响进行了研究,并对界面处不同GR/TC4比例的网状结构复合材料的物相结构、显微组织及室温压缩性能进行了系统性的研究。结果表明,烧结温度和升温速率是影响GR与基体反应程度的主要因素,压力主要影响材料致密度,低温高压快速烧结可以降低GR与基体的反应程度,但高比例的GR残留并没有带来力学性能的大幅提升。对于0.25wt%的GR添加量,GR的反应比例约为70%~80%能得到更加良好的异质界面的结合,获得综合力学性能优异的GR/TC4协同增强的钛合金基复合材料。GR在钛合金基体中的三维网络状分布能调控钛基复合材料的强度与塑性的矛盾。      

Effect of microstructure morphology on mechanical properties of quenching and partitioning steel

In order to illuminate the relationship between microstructure morphology and final properties of the quenching and partitioning(Q&P) steel, the samples with different microstructure morphology (equiaxed and lamellar) and same volume fraction of each phase are obtained by controlling the initial microstructure and Q&P heat treatment. Because of the feature of microstructure morphology, a large yield ratio and total elongation are obtained in the lamellar sample though yield strength and ultimate tensile strength are relatively lower than that of equiaxed sample. Moreover, the lamellar sample produces a continuous work-hardening rate and better the fracture toughness compared to the equiaxed sample. Thus the lamellar sample is more suitable to be used as automotive structural components.     

热变形参数对TA15合金组织的影响及其相变动力学

采用Gleeble-1500热模拟机单道次热压缩变形实验和元胞自动机方法观察模拟了TA15在变形温度为750~1100℃、应变速率为0.01~1s-1范围内的微观组织变化,研究了不同变形参数对等温热压缩过程中微观组织和性能的影响;根据元胞自动机模拟结果,计算其相变动力学。热压缩实验结果表明,该合金属于温度敏感型和应变速率敏感型合金,随着温度的升高或应变速率的降低,β相含量增加;元胞自动机模拟结果表明,相变动力学Avrami指数n在2.0~3.0之间。     

ZrTi-V-Mn-Ni系贮氢合金的相结构与电化学性能研究*

优化合金组成,设计六种锆基AB2型贮氢合金材料。XRD分析表明,当0≤x≤0.5时,Zr1-xTix(NiCoMnV)2.1贮氢合金的主相都是Laves C15,但随Ti含量的增加,Laves C14相含量增多;当用V-Fe(85.6%)合金代替Zr0.6Ti0.4(NiCoMn-VFeCr)1.7中的V时,贮氢合金中Laves C14相的含量几乎可与Laves C15相当。电化学测试表明：Zr0.9Ti0.1(NiCoMnV)2.1贮氢电极的放电容量可达340mAh/g左右,但是随着Ti含量的逐渐增加,合金电极的放电容量降低很快。以适量的（V－Fe)合金取代Zr0.6Ti0.4(NiCoMnVFeCr)1.7合金中的V和Fe,发现合金电极的第一次放电容量就能达到200mAh/g左右,并且其容量稍高于含纯V的合金电极,容量可达315mAh/g左右。     

Effect of hydrogen plasma treatment on the surface morphology, microstructure and electronic transport properties of nc-Si:H

Hydrogenated nanocrystalline silicon (nc-Si:H) films, deposited by reactive radio-frequency sputtering with 33% hydrogen dilution in argon at 200 °C, were treated with low-power hydrogen plasma at room temperature at various power densities (0.1-0.5 W/cm²) and durations (10 s-10 min). Plasma treatment reduced the surface root mean square roughness and increased the average grain size. This was attributed to the mass transport of Si atoms on the surface by surface and grain boundary diffusion. Plasma treatment under low power density (0.1 W/cm²) for short duration (10 s) caused a significant enhancement of crystalline volume fraction and electrical conductivity, compared to as-deposited film. While higher power (0.5 W/cm²) hydrogen plasma treatment for longer durations (up to 10 min) caused moderate improvement in crystalline fraction and electrical properties; however, the magnitude of improvement is not significant compared to low-power (0.1 W/cm²)/short-duration (10 s) plasma exposure. The results indicate that low-power hydrogen plasma treatment at room temperature can be an effective tool to improve the structural and electrical properties of nc-Si:H.     

Investigation of effects of dibutyltin dilaurate on reaction injection molding polyurethane-urea kinetics,morphology and mechanical properties by FTIR

The bulk catalyst effect of dibutyltin dilaurate (DBTDL) on the reaction of NCO respectively with OH and NH₂ was investigated in detail. The results showed that DBTDL had specific catalyst effect on the reaction of NCO with OH and no measurable effect on the reaction of NCO with NH₂. In situ Fourier transform infrared spectroscopy (FTIR) used in the reaction injection molding (RIM) process showed that with increasing the concentration of DBTDL, the formation rate of the soft segment became fast, and the order degree of urea carbonyls became worse. Meanwhile, more arrange manners of urea carbonyl were present. The bands at 1653, 1647 and 1637 cm^-1 were able to be detected at the low conversion. No hydrogen-bonded urea carbonyl available in the spectra at the beginning. The tensile-stress behavior showed that, with the increase of the DBTDL content, the interaction between polar groups became weak, while the virtual crosslinks also became weak. Although the break stress (?), 300%? and the hardness of elastomers decreased obviously, however, the tear strength, associated with the morphology of polyurethane-urea (PUU), showed the maximum when the DBTDL content was 2.63‰.     

Effect of austenite grain size and bainite morphology on overall kinetics of bainite transformation in steels

Abstract

An attempt is made to rationalise some contradictory observations on the effect of austenite grain size on the overall kinetics of the bainite transformation in steels. Experiments have been carried out on two steels which show opposite effects of austenite grain size on the reaction rate. General equations describing the reaction rate are derived by taking into account the morphology of the bainite in each steel. The equations derived can explain the contradictory effects of the austenite grain size on the overall reaction rate. The results are also found to be in good agreement with the published data.     

热处理对BT14钛合金显微组织和力学性能的影响

本文研究了BT14钛合金热处理规范→显微组织→力学性能之间的关系.结果表明:热处理工艺对组织和力学性能的影响很大.其中,随着退火温度的升高,初生α相含量逐渐减小,α相颗粒逐渐粗化,向等轴状发展;随着退火温度的升高,合金的强度和硬度逐渐减小,但塑性变化是先升高后减小的趋势.热处理强化规范中低温淬火 低温时效所得的合金综合性能较优.但BT14钛合金强化效果不明显.     

Effect of elevated annealing temperature on the morphology, microstructure, conductivity and microwave absorption properties of phthalocyanine polymer

An aromatic, diether-linked phthalocyanine resin (Pc) was prepared from 4,4′-bis (3,4-dicyanophenoxy) biphenyl (BPh) and investigated for morphology, microstructure, dielectric, conductivity and microwave absorption properties at different annealing temperatures from 300 to 800 °C. The results showed that the annealing temperature could significantly change the morphology and microstructure of the Pc polymer, leading to the generation of carbon-Pc polymer composites, and enhance the microwave absorbing and electrical properties of the Pc polymer. The dramatic electrical and dielectric transition happened when the annealing condition was 550 °C 24 h. The conductivity of the samples exhibited a transition of electrical behavior from an insulator to semiconductor of approximately 10⁺² S/cm. Pc polymer exhibited excellent microwave absorption properties in the frequency range of 0.5–18.0 GHz after sintering process. The microwave absorption of the annealing Pc polymer can be mainly attributed to the dielectric loss rather than magnetic loss. The sample annealed at 500 °C 24 h had two strong microwave absorbing peaks and achieved a maximum absorbing value of ?44 dB around 10.7 and 17.5 GHz when the thickness was 3.0 mm. The novel carbon-Pc polymer composites were believed to have potential applications in the microwave absorbing area.     

Effect of reaction conditions on the morphology and optical properties of ZnO nanocrystals

We report a simple hydrothermal method at low temperature for synthesis of zinc oxide (ZnO) nanorods followed by ultrasonication. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), UV–Vis absorption spectrophotometer and photoluminescence (PL) spectroscopy. The XRD results shows the prepared ZnO nanocrystals are in wurtzite structure. TEM results indicate the growth of ZnO nanorods with increasing reaction stirring time and morphology also get affected after ultrasonication. PL studies also reveal the presence of defects considered as the main reason for the green emission in PL with increasing reaction time and blue shift in UV emission corresponds to reduction of tensile strain.     

超音速微粒轰击对TC11钛合金组织和疲劳性能的影响

采用超音速微粒轰击(SFPB)技术对层片组织的TC11钛合金进行表面纳米化处理,对比研究了表面纳米化处理前、后TC11钛合金的室温高周疲劳行为;借助光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)和X射线衍射仪(XRD)对比分析了高周疲劳断口及断口附近的微观组织形貌.结果表明:经SFPB处理后在钛合金表层产生了30～50μm厚的纳米层,纳米晶尺寸在5～15 nm左右;疲劳性能得到明显提高,在相同应力级别下的疲劳寿命提高了约8～10倍,疲劳条带宽度变窄,且随着加载级别的降低,疲劳寿命提高的倍数逐渐增加;SFPB前、后疲劳断口均由疲劳源区、裂纹扩展区、瞬断区三部分组成,但SFPB处理后的疲劳源由处理前的表层移至次表层;SFPB处理态试样疲劳加载后表层组织仍为纳米量级,但次表层组织中出现大量的形变孪晶、位错缠结以及少量的形变诱导马氏体组织.     

Role of aluminum ion implantation on microstructure, microhardness and corrosion properties of titanium alloy

Ti-Al-Zr alloy was implanted with Al at cumulative doses between 1 × 10¹⁷ and 1 × 10¹⁸ ions/cm². The results indicate that the Al-implanted layers are ∼0.1 μm thick and are composed almost entirely of an amorphous layer. Implanted layer hardness is dose dependent and is increased by more than a factor of 4 for the high-dose implanted specimen when compared with that of the substrate material. The corrosion resistance of the sample was markedly improved after aluminum implantation.     

Effect of nanosilica addition on the physicomechanical properties,pore morphology,and phase transformation of freeze cast hydroxyapatite scaffolds

Freeze casting technique is a simple and effective method for the fabrication of porous ceramic structures. The objective of this work is to study the production and characterization of hydroxyapatite/nanosilica (HA/nSiO₂) scaffolds fabricated through this method. In the experimental procedure, the solidified samples were prepared by slurries containing different concentration of HA and nSiO₂ followed by sintering procedure at 1200 and 1350 °C. The phase composition, microstructure, and compressive strength of the scaffolds were characterized by X-ray diffraction, scanning electron microscopy, and mechanical strength test. It was found that the porosity of the scaffolds was in the range of 30–86.5 % and the value of compressive strengths lied between 0.16 and 71.96 MPa which were influenced by nSiO₂ content, cooling rate, and sintering temperature. With respect to porosity, pore size, and compressive strength, the scaffolds with 5 % nSiO₂, the cooling rate of 1 °C/min and the sintering temperature of 1350 °C showed preferable results for bone tissue engineering applications.     

Ti添加对WC-Ni3Al硬质合金微观组织与力学性能的影响

为提高WC-Ni₃Al硬质合金的力学性能,采用放电等离子烧结制备Ti掺杂的WC-Ni₃Al硬质合金,并研究不同Ti添加量对WC-Ni₃Al硬质合金微观组织和力学性能的影响。结果表明:Ti的添加减小WC-Ni₃Al块体样品中反应生成的少量Al₂O₃的尺寸,并且使Al₂O₃的分布更加均匀。一方面,小尺寸的Al₂O₃与原位生成的(Ti,W)C协同提高WC-Ni₃Al块体样品的硬度;另一方面,适量Ti的添加还提高WC-Ni₃Al硬质合金的断裂韧度,这是由于原位生成的(Ti,W)C与WC有较好的界面结合,增加对裂纹扩展的桥接与偏转作用。当添加3%(质量分数)的Ti时,WC-Ni₃Al硬质合金获得了优异的力学性能,硬度和断裂韧度分别为(19.29±0.18)GPa和(13.14±0.24)MPa·m^1/2。     

Effects of processing conditions on microstructure and mechanical properties of equal-channel-angular-pressed titanium

This review presents an investigation on effects of the processing conditions on the microstructural evolution and mechanical properties of commercial pure titanium processed by Equal Channel Angular Pressing (ECAP). An overview of ECAP processing is presented. A discussion on the microstructure evolution of ECAPed titanium emphasising effects of the ECAP-route type, processing temperature, number of ECAP passes, and mechanical/thermal treatments is presented. Moreover, the variations of the mechanical properties (yield strength, tensile strength, and ductility) of titanium as functions of the grain size are reported for the different conditions of ECAP processing. In addition, the best estimates of the Hall–Petch parameters for titanium processed by ECAP, ECAP followed by mechanical and/or thermal annealing are reported.     

Preparation,microstructure and mechanical properties of porous titanium sintered by Ti fibres

Open-cell porous Ti with a porosity ranging from 35 to 84% was successfully manufactured by sintering titanium fibres. The microstructure of the porous titanium was observed by SEM and the compressive mechanical properties were tested. By adjusting the spiral structure of the porous titanium, the pore size can be controlled in a range of 150–600 μm. With the increasing of the porosity, compressive yield strength and modulus decrease as predicated. However, high mechanical properties were still obtained at a medium porosity, e.g. the compressive yield strength and the modulus are as high as 100–200 MPa and 3.5–4.2 GPa, respectively, when the porosity is in the range of 50–70%. It was suggested that the porous titanium be strong enough to resist handing during implantation and in vivo loading. It is expected to be used as biocompatible implant, because their interconnected porous structures permit bone tissues ingrowth and the body fluids transportation.     

Hydrous oxides of titanium: cation exchange properties and kinetics of exchange

The ion exchange properties of hydrous titania gels of different particle sizes, precipitated from titanous chloride through the agency of ammonium carbonate and hydroxide have been studied. Such studies were carried out under acidic and alkaline conditions with respect to Cu²⁺, Ni²⁺, Co²⁺ and Cr³⁺ ions.In the case of gels precipitated by ammonium carbonate, oxygen gas was used as the oxidizing agent whereas with ammonium hydroxide as precipitant, oxidation was performed with hydrogen peroxide.Ion exchange capacities were determined by visible spectrophotometry. Increasing the pH of preparation lead to an increase in exchange capacities of the hydroxide precipitated gels that are characterized to be mesoporous. Such an increase is not observed in the case of carbonate precipitated microporous gels. It is shown that in the latter case the NH ₄ ⁺ ions generated by the initial interaction of (NH₄)₂CO₃ with the acidic titanous chloride lead to the formation of titania exchangers that are predominantly in the ammonium form. The textural characteristics of the exchanger resulting from different conditions of preparation is a significant contributing parameter to the resulting data.Ageing of the microporous titania samples markedly reduces the exchanger capacity of the smaller Ni²⁺ ions but increases that of the bulkier Cr³⁺ as a result of the presence of some wide pores that appear upon agglomeration. The presence of Cr³⁺ ions in the hydroxo form in solution seems to inhibit its exchange with the appropriate surface species.Studies on the kinetics of exchange with respect to the Ni²⁺ ions seem to indicate that a particle diffusion mechanism is partly or completely responsible for the rate of exchange.