热变形条件对激光增材制造TC18钛合金组织及变形行为的影响

通过单轴等温热压缩实验,研究了激光增材制造TC18钛合金在不同变形条件下的热变形行为,分析了其流变应力-应变规律和动态软化机制,建立了峰值应力本构方程。结果表明,激光增材制造TC18钛合金的流变应力-应变曲线表现为连续软化和稳态流变两种特征,其激活能为476.8kJ·mol~(-1)。当热加工温度处于α+β两相区时,软化机制为动态回复;而当热加工温度处于β单相区时,软化机制为动态再结晶。激光增材制造TC18钛合金较理想的热加工工艺参数:变形温度为830~880℃、应变速率为0.001~0.003s~(-1)和变形温度为750~760℃、应变速率为0.001~0.002s~(-1)。     

EBSD研究热变形双相不锈钢的微区取向分布

利用电子背散射衍射(EBSD)技术分析了两种热模拟单向压缩条件下(变形温度为1 050℃,应变速率为0.1 s-1和变形温度为1 150℃,应变速率为1s-1)2507超级双相不锈钢的微区取向分布.结果表明:实验钢的铁素体在两种实验条件下均可形成〈001〉和〈111〉织构;奥氏体在变形温度为1 150℃,应变速率为1 ...     

车用双相钢激光焊接接头组织性能研究

为提高汽车车身用双相(DP)钢焊接构件在动态载荷下应用的可靠性,利用脉冲Nd:YAG激光器,对DP600进行激光对接焊,利用光学显微镜、扫描电子显微镜、显微硬度计、材料拉伸试验机等分析测试手段,研究了焊接接头的显微组织和高应变速率下的拉伸性能。结果表明,在合适的脉冲激光焊接参数下,DP600钢板可获得成形均匀的激光深熔焊缝。焊接接头的焊缝区(WZ)主要为马氏体组织,硬度高于母材;热影响区(HAZ)较窄但存在马氏体回火软化现象。焊接接头力学性能对应变速率较为敏感,随应变速率的增加,屈服强度和抗拉强度增加,而塑性均小于母材。不同应变速率下DP600对接焊拉伸断口均为韧窝形貌,呈典型的韧性断裂特征。     

铍青铜(QBe2)超塑性的研究

本文对硬态铍青铜(QBe2)的超塑性力学行为和组织变化进行了研究。合金在温度为450～640℃和应变速率为1.95×10~(-4)～1.67×10~(-2)S~(-1)的范围内拉伸,能呈现较好的超塑性效应。当合金在550℃下以1.95×10~(-4)S~(-1)的应变速率拉伸时,延伸率可达780％。在较低的应变速率下拉伸。合金具有各向异性。在550℃下以8.33×10~(-4)S~(-1)的应变速率拉伸时,拉伸方向与原材料轧制方向成0°、45°和90°角的试样,延伸率分别为550％、860％和675％。而在较高的应变速率下拉伸,这种塑性差异消失。合金不需预先处理便可进行超塑性变形,通过动态再结晶使原始形变组织转化为微细等轴晶粒,同时利用第二相粒子对晶界的钉扎来控制晶拉粗化。拉伸后的试样在光学显微镜下观察未发现空洞,但试样的断裂却是由空洞的连接所致。     

SLM成形316L不锈钢热变形行为研究

利用Gleeble-3800热模拟压缩试验机研究激光选区熔化(SLM)成形316L不锈钢在变形温度为900～1 100℃、应变速率为0.001～1 s^-1时的热变形行为。结果表明，在变形过程中，流变应力会随着变形温度的升高或应变速率的降低而显著降低；建立了适用于变形全过程的应变修正双曲正弦本构模型，并利用统计学参数评估模型精度，其R值高达0.988 63,平均相对误差绝对值为5.45%;绘制激光选区熔化成形316L不锈钢在应变为0.9时的热加工图，结合不同加工区域内微观组织分析，表明失稳机制为绝热剪切带的形成和流动局部化，SLM成形316L不锈钢适合在低应变速率和高温高应变速率条件下进行加工。     

EBSD研究热变形双相不锈钢的微区取向分布

利用电子背散射衍射(EBSD)技术分析了两种热模拟单向压缩条件下(变形温度为1 050℃,应变速率为0.1 s-1和变形温度为1 150℃,应变速率为1 s-1)2507超级双相不锈钢的微区取向分布。结果表明:实验钢的铁素体在两种实验条件下均可形成〈001〉和〈111〉织构;奥氏体在变形温度为1 150℃,应变速率为1 s-1条件下获得更多数量的以Σ3为主的CSL特殊晶界;两种实验条件下,2507超级双相不锈钢中铁素体和奥氏体均发生了动态再结晶;在铁素体向奥氏体转变过程中,奥氏体可以在铁素体晶界处生成,也可以在铁素体晶粒内部形成。     

平面应变压缩过程中初始取向对AZ31镁合金变形行为的影响

在室温和150℃下对AZ31镁合金进行平面应变压缩试验,应变速率为0.01 s-1,形变量为0.1.试样(切割于强织构的热轧板)的压缩轴c与其基面法向成不同的角度,从而研究初始织构对AZ31镁合金塑性变形行为的影响.利用电子背散射衍射花样(EBSD)采集变形试样的微观结构和织构信息,分析孪生和滑移行为.实验发现AZ31镁合金塑性变形由{10(-12)}<(-10)11>拉伸孪生和基面滑移共同控制,并确定了各种变形模式比例与晶体初始取向的关系,其中拉伸孪生在压缩轴垂直于c轴方向时占主导作用.     

激光冲击处理304不锈钢表面的形貌特征及其机理分析

为了研究激光冲击强化(LSP)过程中冲击波柔性加载条件下靶材的表面形貌与变形机理的联系,采用短脉冲强激光对304奥氏体不锈钢表面进行LSP处理,在没有对材料表面进行腐蚀的条件下,利用光学显微镜直接观察了LSP处理后材料的表面,并分析了其表面形貌特征与形成机理。研究发现,表面形貌呈现了多晶面心立方(FCC)金属的塑性变形特征,所浮现的形变组织能够直接反映材料在冲击波加载下的变形机制。实验结果表明,激光冲击后材料的表面形貌与塑性变形机制具有对应关系,这为LSP处理的变形机理的研究提供了一种新的实验方法。     

Nd∶YAG连续激光烧蚀碳纤维复合材料的过程观测

通过Nd∶YAG激光辐照碳纤维/环氧树脂复合材料过程的高速摄像观测,得到了不同辐照功率密度下烧蚀过程中的主要现象。发现在低功率密度(50 W/cm2)下,主要是表面烧蚀机制,不会发生燃烧现象,在长时间辐照下,由于表层附近出现轻微的聚合物焦化分解,表面层出现粉末状和漂絮状的碳粉缓缓弥散空气中;在中等功率密度(300 W/cm2)下,体烧蚀机制占主要地位,内层分解气体喷出,在空气中点燃引起表面燃烧,主要燃烧表面聚合物;在高功率密度(4500 W/cm2)下是以表面烧蚀为主的质量迁移机制,在极短的时间(0.001 s)内表面层被破坏,瞬间燃烧,光斑中心出现喷射式的气化等离子体现象,并出现逐层烧蚀和各向异性热传导引起的烧蚀区形貌变形等现象。     

激光冲击奥氏体不锈钢表面的亚结构变化

采用高能短脉宽激光冲击加载技术(LSP)，利用扫描电子显微镜(SEM)，X射线衍射(XRD)和透射电子显微镜(TEM)等手段，研究了在激光诱导的超高应变率和高于材料动态屈服强度冲击加载条件下，2Cr17Mn15Ni2N奥氏体不锈钢表面亚结构的转变特征和机制。结果表明，冲击区表面结晶度降低，形成大小为0．1～0．5μm的等轴亚晶区以及规则排列的龟裂区；表面硬度显著增加，形变层深0．25mm；此外，在冲击区表层观察到形变滞后退火孪晶、显微带、位错胞、条形亚晶、滑移型层错等亚结构，未发现形变孪晶和ε(α)马氏体相。分析认为，激光诱导的超高应变率是产生奥氏体不锈钢表面特殊亚结构的主要原因。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-