Sushma Bhat and P.N.Kotru(Dept. of Physics
,
Uuiversity of Jammu
,
Jammu -180 001
,
India) M.L.Koul(Dept. of Chemistry
,
Uuiversity of Jammu
,
Jammu
,
India)
材料科学技术（英文）
Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamolybdate crystals are associated with thirty water molecules;the composition being La2Mo7O24.3OH2O. It is shown that all the thirty water molecules associated with lanthanum heptamolybdate crystal are lost during its decomposition, leading to its anhydrous form. Results obtained on application of TG based models, viz. Horowitz-Metzger,Coats-Redfern and Piloyan-Novikova and of DSC based methods viz. Roger-Morris-Smith and Barret, regarding solid state reaction kinetics are also reported. The random nucleation model is shown to be the one that is relevant to the decomposition of lanthanum heptamolybdate. The kinetic parameters, viz.the order of reaction. frquency factor, energy of activation and entropy using above mentioned models are computed and shown to bear reasonably good agreement
关键词:
罗子江
,
周勋
,
王继红
,
郭祥
,
丁召
材料导报
GaAs的高迁移率与其表面重构和表面形貌有密切关联,对于GaAs表面重构的研究一直是研究低维半导体的重点和难点.重点回顾了几十年来研究者们对于GaAs(001)表面重构的研究成果,结合所在实验室最近的实验数据,对GaAs(001)表面重构的相关研究成果进行了汇总和遴选,重点讲述了在实际应用中常用的几种表面重构;从富As表面的C(4×4)重构、不同(2×4)重构到逐渐富Ga的(n×6)重构、(4×2)重构,结合RHEED衍射花样、STM扫描图片以及球棍模型,对它们的倒、实空间图像以及理论模型都进行了深入的探讨和研究,为将来进行GaAs(001)表面的更深入研究打下基础并提供数据和理论支持.
关键词:
RHEED
,
STM
,
GaAs(001)
,
表面重构
毕大森
,
武晋
,
张建
,
彭本栋
材料开发与应用
doi:10.3969/j.issn.1003-1545.2009.01.003
高强度烘烤强化(BH)钢是汽车覆盖件用的高强度钢板.本文通过试验对汽车用高强度钢板B180H1的力学性能、成形性能、烘烤硬化性能和抗凹陷性能进行了全面的研究,并与DC04钢板的各项性能进行了比较.使用NADDRG模型对B180H1钢的成形极限进行了预测.试验结果表明,B180H1的力学性能优于DC04,成形性能不低于DC04,且B180H1的烘烤硬化性能及抗凹陷性能方面均优于DC04.B180H1钢板的实冲壳体也具有良好的成形性能.
关键词:
汽车轻量化
,
高强度钢板
,
烘烤硬化
,
成形性能
,
抗凹陷性
Fatih Hayat
材料科学技术（英文）
In this study, resistance spot weldability of 180 grade bake hardening steel (BH180), 7123 grade interstitial free steel (IF7123) and 304 grade austenitic stainless steel (AISI304L) with each other was investigated. In the joining process, electrode pressure and weld current were kept constant and six different weld time were chosen. Microstructure, microhardness, tensile-shear properties and fracture types of resistance spot welded joints were examined. In order to characterize the metallurgical structure of the welded joint, the microstructural profile was developed, and the relationship between mechanical properties and microstructure was determined. The change of weld time, nugget diameter, the HAZ (heat affected zone) width and the electrode immersion depth were also investigated. Welded joints were examined by SEM (scanning electron microscopy) images of fracture surface. As a result of the experiment, it was determined that with increasing weld time, tensile shear load bearing capacity (TLBC) increased with weld time up to 25 cycle and two types of tearing occurred. It was also determined that while the failure occurred from IF side at the BH180+IF7123 joint, it occurred from the BH180 side at the BH180+AISI304L joint.
关键词:
Resistance spot welding
段建平
钢铁
针对180tRH精炼工艺存在的真空度低、超低碳钢处理时间长、钢中氧含量高以及脱硫效率低等问题，研究并优化了RH真空脱气、脱碳升温、脱氧、脱硫等工艺，使RH工作真空度提高到100Pa以下，超低碳钢处理时间缩短至平均36.5min，超低碳钢钢中氧含量最低13×10-6。优化工艺降低了钢中[H]、[N]、[C]、[O]、[S]等元素的含量，提高了钢水洁净度，缩短了RH精炼时间，提高了RH精炼生产率。
关键词:
陈军利
,
康志强
钢铁研究
邯钢邯宝炼钢厂在生产CR180BH钢过程中成品w(C)控制不准,主要原因是RH脱碳过量,使w(C)产生较大波动,且在过程增碳环节上把握不准.通过建立RH脱碳模型以及严格控制钢水进站条件,RH进站w(O)控制在0.05％～0.075％,进站w(C)控制在0.03％～0.05％,从而实现RH脱碳终点w(C)稳定控制;同时加强合金辅料检查,加强连铸用耐材质量管理,使w(C)得到精准的控制,成品w(C)稳定控制在0.002 0％～0.003 0％,成分命中率从86％提高到96％.
关键词:
RH脱碳模型
,
烘烤硬化钢
,
w(C)
段建平
钢铁
针对180t RH精炼工艺存在的真空度低、超低碳钢处理时间长、钢中氧含量高及脱硫效率低等问题,研究并优化了RH真空脱气、脱碳升温、脱氧、脱硫等工艺,使RH工作真空度提高到100Pa以下,超低碳钢处理时间缩短至平均36.5min,超低碳钢钢中氧的质量分数最低为13×10-6.优化工艺降低了钢中[H]、[N]、[C]、[O]、[S]等元素的含量,提高了钢水洁净度,缩短了RH精炼时间,提高了RH精炼生产率.
关键词:
RH精炼
,
工艺技术
,
洁净钢
沈海军
,
穆先才
材料研究学报
doi:10.3321/j.issn:1005-3093.2006.01.020
采用分子动力学方法模拟了C60、C180、C60@C180富勒烯分子的压缩过程,用PM3半经验量子力学方法计算了压缩C60、C180、C60@C180分子的电子结构,讨论了C60、C180、C60@C180分子压缩力学特性的差异,以及电子结构在压缩过程中的变化.结果表明,由于分子几何构形上的差异,C60分子的承载与吸收能量能力显著高于C180和C60@C180分子,而C60@C180分子略高于C180分子;C60分子具有最高的化学稳定性,而C60@C180分子的稳定性最低;C60和C60@C180分子的压缩变形越大,越容易失去电子,稳定性越低;C180分子在加载点处发生压缩"塌陷"时,化学活性明显增加.
关键词:
材料科学基础学科
,
分子动力学
,
量子力学
,
富勒烯
,
力学特性
,
电子结构
刘梅
,
陈芳慧
,
王永红
,
张玉梅
,
李海波
兵器材料科学与工程
doi:33-1331/TJ.20110704.2224.006
采用直流磁控溅射在表面氧化的Si (001)基片上制备了FePt/C纳米薄膜,将薄膜样品经过600℃真空退火处理1h获得L10-FePt薄膜.用X射线衍射仪(XRD)、振动样品磁强计(VSM)和扫描探针显微镜(SPM)对样品的结构、磁性和表面形貌进行测量和分析.结果表明:随着C底层厚度的增加,L10-FePt薄膜(001)取向度增强,有序化程度提高,矫顽力增大；C溅射时间为180s时,获得了具有(001)织构生长的L10-FePt薄膜.
关键词:
磁控溅射
,
FePt合金
,
织构
,
磁性
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Friction stress and back stress of [001] Cu single crystals during cyclic deformation were derived from cyclic stress-strain hysteresis loops by using the Cottrell method and the results are compared with those for single slip crystals. The cyclic hardening features of the [001] crystals are described in terms of the friction stress and back stress. Specific, detailed study was carried out on the sample cycled with a plastic strain amplitude of 1.8 x 10(-3). It has been shown that both the 'true' friction stress, i.e. the cyclic yield stress, and the back stress in the [001] crystals increase much more rapidly than those in single slip crystals in the hardening stage. In the saturation stage, however, only the friction stress in the [001] crystal is higher than its correspondent in the single slip crystals, while the back stresses in these two types of crystals are close to each other. The higher friction stress in the [001] crystal is related to the higher density of jogs produced by the dislocation reactions between the primary and critical slip systems, and the existence of secondary dislocations in channels. The higher back stress in the hardening stage is attributed to the higher dislocation density in loop patches introduced by dislocation reactions in the first dozen of cycles. By modifying the Kulhlmann-Wilsdorf and Laird model, it is possible now to express quantitatively both the back stress and the shear stress in a cyclically deformed crystal with a particular orientation as functions of the applied strain amplitude as well as an orientation-dependent factor: the hardening coefficient for the first stage of unidirectional deformation. The predictions from these expressions for multiple slip crystals are in very good agreement with experimental data. (C) 1998 Elsevier Science S.A. All rights reserved.
关键词:
friction stress;back stress;multiple slip crystals;KW-L model;double slip;deformation-behavior;stress
