A.Wiengmoon
,
T.Chairuangsri
,
N.Chomsang
,
N.Poolthong
,
J.T.H.Pearce
材料科学技术（英文）
Effects of heat treatments on hardness and dry wear properties of a semi-solid processed Fe-26.96 wt pct Cr-2.91 wt pct C cast iron were studied. Heat treatments included tempering at 500℃, destabilisation at 1075℃ and destabilisation at 1075℃ plus tempering at 500℃, all followed by air cooling. Electron microscopy revealed that, in the as-cast condition, the primary proeutectic austenite was round in shape while the eutectic M7C3 carbide was found as radiating clusters mixed with directional clusters. Tempering did not change the microstructure significantly when observed by scanning or transmission electron microscopy. Destabilisation followed by air cooling led to a precipitation of secondary M23C6 carbide and a transformation of the primary austenite to martensite. Precipitation behaviour is comparable to that observed in the conventionally cast iron. Tempering after destabilisation resulted in a higher amount of secondary carbide precipitation within the tempered martensite in the eutectic structure. Vickers macrohardness and microhardness in the proeutectic zones were measured. Dry wear properties were tested by using a pin-on-disc method. The maximum hardness and the lowest dry wear rate were obtained from the destabilisation-plus-tempering heat treatment due to the precipitation of secondary carbides within the martensite matrix and a possible reduction in the retained austenite.
关键词:
Semi-solid process
,
null
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null
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null
,
null
H. Y. Zhao
,
A. L. Lu
,
Q. Y. Shi and F. Yan (Welding Division
,
Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)
金属学报(英文版)
T-joints are widely used in ship manufacturing and other welding structures.The welding residual stress and deformation hare significant influence on failure and service life in welding structures.By us- ing of 3D thermal elasto - plastic FEM, the temperature fields,stress fields and deformation of weld- ing processes on T - joints are analyzed in this paper.The moving heat source is considered in the com- putation. Moreover, weld metal filling and multiple - pass welding are simulated using activate/deac- tivate ability.For avoiding "locking" in full integration elements of welding computation,the re- duced intergration elements are used in weld area.The nonlinear FEM analysis program MARC is used to complete the computations, as well as its user subroutines that are programmed to develop the special techniques needed in the simulation of welding process.Some different welding procedures are com- pared, and the welding residual stress and deformation are discussed in details.
关键词:
welding
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null
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null
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null
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null
Chinese Physics Letters
The magnetic properties of 1 T-TaS2 and 1 T-Fe-0.07 Ta-0.93 S-2 have been studied, Experimental results show that the phase transition temperature of 1 T-TaS2 is a function of the magnetic field, At low temperatures, both compounds are in a mixed state of charge density wave -spin density wave due to the coherent superposition of antiferromagnetic coupling.
关键词:
density
李东风
,
王浩静
,
贺福
,
王心葵
新型炭材料
doi:10.3969/j.issn.1007-8827.2007.01.011
利用SEM、元素分析、XRD和激光Raman光谱研究了T300和T700的形貌、化学组成和微观结构参数.结果发现:T700炭纤维表面光滑,而T300炭纤维的表面有大量的沟槽.表明前者是用干喷湿纺原丝,后者是用湿法纺丝原丝.两种纤维的断面均呈现出颗粒状特征.T700的含碳量高于T300,含氮量低于T300.两者的微观结构参数(d002、La和Lc)差异佐证了T700的炭化温度高于T300.T700的择优取向角Z比T300小2.3°,是石墨微晶致密有序排列的反映,因而使其体密度比T300高2.27%,空隙率低7.54%.所以致密化赋予了T700较高的拉伸强度.
关键词:
PAN基炭纤维
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微观结构
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XRD
,
Raman光谱
孙长征
,
宇波
,
魏进家
工程热物理学报
通过分析气相、液相、管壁之间的关系,将气液混输管道中的流型划分为五种,并总结了各流型的特点及气液相和管壁间的几何关系;在对Baker、Brill、Beggs-Brill、Taitel、段塞特征分析(SCA)等流型判别方法进行分析的基础上,提出了一种综合使用SCA、Taitel和Brill三种方法的流型判别方法 S-T-B法.经算例验证,该方法对气液两相混输的流型判断准确性较高,可以作为气液混输工艺计算过程中确定流型的方法.
关键词:
气液混输
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流型
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段塞特征分析法
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S-T-B
周光
,
杨新岐
,
徐效东
,
张照华
航空材料学报
doi:10.3969/j.issn.1005-5053.2012.4.005
对板厚3mm的6061-T4铝合金T型接头进行搅拌摩擦焊接研究并具体讨论了旋转速率(ω)及焊接速率(ν)对焊接缺陷及力学性能的影响.结果表明:对给定的夹具形式和搅拌工具,当ν不变时焊缝前进侧筋板圆角过渡处容易产生随ω/ν增大而减小的隧道缺陷,后退侧圆角区易出现清晰的“Z”连接线；壁板出现两个随ω增大而扩大的软化区域,而壁板焊缝中心的硬度随ω增大而升高；T型接头筋板焊缝热力影响区同样被软化,其硬度较母材降低17.0％；局部组织软件是造成所有接头沿壁板方向加载抗拉强度下降的重要原因,其最高抗拉强度只达到母材的73.8％,隧道缺陷是引起ω=1008r/min筋板方向强度降低的主要原因,而ω=1541r/min和ω=2256r/min筋板方向强度降低主要归结于T型接头中热力影响区组织的软化,其中当ω/ν=1541/218 r/mm时,沿T接筋板方向抗拉强度最高可达到母材的83.5％.
关键词:
搅拌摩擦焊
,
T型接头
,
焊接缺陷
,
力学性能
何志宏
,
李宝华
,
唐众民
,
鄢江武
兵器材料科学与工程
doi:33-1331/TJ.20110905.2223.006
采用3种规格的搅拌头进行2A70-T6铝合金T型接头搅拌摩擦焊试验,并对焊缝横截面进行观察以及焊缝抗拉强度的测试.结果表明:焊缝中前进侧过渡区的金属变化急剧,拉长的晶粒成流线状分布,返回侧过渡区的金属变化缓和,由焊核区细小晶粒缓慢过渡至母材较大的晶粒;随着搅拌针根部直径的增加,焊核的宽度也增大;为了获得无缺陷的接头,焊接速度增大时,顶锻压力必须协同增大,随着顶锻压力的增大,焊缝的抗拉强度也增大.
关键词:
2A70-T6
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铝合金
,
T型接头
,
搅拌摩擦焊
Communications in Theoretical Physics
For the first time, by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d(3) electronic configuration, the values of parameters in expressions of Raman and optical-branch terms of thermal shifts (TS) due to EPI for three levels, T-4(2) band and T-4(1) band of ruby have been evaluated; the contributions to TS of T-4(2) and T-4(1) broad bands from thermal expansion have also been. calculated; and then, the TS of the peak energies of 'T2 and 4 Ti broad bands have been calculated. The results are in satisfactory agreement with observed data. The values of single-electron reduced matrix elements representing the strengths of EPI of T-4(2) and T-4(1) bands have respectively been determined. For TS of the peak energies of T-4(2) and T-4(1) bands, it is found that the contribution to TS from the second-order term in EPI Hamiltonian is dominant; TS due to EPI of acoustic branches are over two times as much as those of optical branches, and both of them increase rapidly with temperature; the neighbor-level term is insignificant; the contribution to TS from thermal expansion is specially important, and all the three terms of TS of T-4(2) or T-4(1) band axe red shifts.
关键词:
crystal fields;optical spectral bands;electron-phonon interaction;thermal expansion;thermal shift;theoretical calculations;high-pressure;field;spectroscopy;spectra
