W.F. Zhang
,
Y.M. Chen and J.H. Zhu(State Key Laboratory for Mechanical Behavior of Materials
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China)
金属学报(英文版)
A new non-uniform yield phenomenon is found during tension of austenite stainless steel at -190℃, which consists of elasto-plastic instability ξph and stress plateau ξL resulting from strain-induced martensite transformation. It is essentially different from non-uniform yield that is related to dislocation obstacles. The experimental results show that ξph and ξL increase with increaslng strain rate, and ξph, increases but ξL decreases with increasing prestmin.Tronsformation enengy of strain-induced martensite keeps a constant, 3.85×106J/m3, with increasing strain at the stages of both elasto-plastic instability and stress plateau.
关键词:
non-uniform yield
,
null
,
null
,
null
熊进辉
,
黄继华
,
薛行雁
,
张华
,
赵兴科
,
林国标
航空材料学报
doi:10.3969/j.issn.1005-5053.2009.6.010
本文利用AgCuTi-W复合钎料作中间层,在适当的工艺参数下真空钎焊C_f/SiC复合材料与Ti合金,利用SEM,EDS,XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.研究结果表明:钎焊时,复合钎料中的Ti借助Cu-Ti液相与C_f/SiC复合材料反应,在C_f/SiC复合材料与连接层界面形成Ti3SiC2,Ti3Si和少量TiC化合物的混合反应层.复合钎料中的Cu与Ti合金中的Ti发生互扩散,在连接层与Ti合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成W颗粒强化的致密复合连接层,W颗粒主要分布在Cu-Ti相中.W的加入缓解了接头的残余热应力,C_f/SiC/AgCuTi-W/TC4接头剪切强度明显高于C_f/SiC/AgCuTi/TC4接头.
关键词:
C_f/SiC
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Ti合金
,
钎焊
,
AgCuTi-W
汪华剑
,
方庆艳
,
姚斌
,
雷霖
,
段学农
,
赵云辉
,
汪毅冈
,
周怀春
工程热物理学报
本文通过数值模拟和在实际锅炉上的试验,研究了310 MW Foster Wheeler技术w型火焰锅炉F层二次风下倾15°对炉内燃烧过程的影响.通过对模拟和试验的分析表明,F层二次风下倾后对炉内燃烧的影响主要表现在火焰行程延长,煤粉停留时间增加,还原区扩大,一次风与二次风的混合推迟等方面.试验和模拟结果都表明,F层二次风下倾后锅炉的火焰中心下降,飞灰含碳量降低,锅炉效率提高且NOx排放明显减少.
关键词:
W型火焰锅炉
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F层二次风下倾
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煤粉燃烧
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提高效率
,
降低NOx
HUANG Huimin CHEN Xinmin Central South University of Technology
,
Changsha
,
China HUANG Huimin Associate Professor
,
Department of Chemistry
,
Central South University of Technology
,
Changsha
,
China
金属学报(英文版)
The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly chemisorbed oxygen and the interstitial oxygen which could form an interstitial solid solution with β-W.It seems better to consider β-W to be a metastable phase of tungsten with the interstitial oxygen as stabilizer.
关键词:
tungsten
,
null
,
null
,
null
Physical Review B
The effect of W on the structural stability of TiAl intermetallic systems and the site preference of W in B2 and L1(0) TiAl were studied based on first-principles calculations. It was found find that about 15 at. % W addition, in good agreement with experiment, is required to stabilize the B2 structure in a TiAl base alloy. W was predicted to occupy Al sites in the B2 phase, but Ti sites in the L1(0) phase. The B2-stabilizing effect of W and its site preference can be explained perfectly on the basis of the pseudogap effect and the strong covalent W-Ti bonding. The strong W-Ti bonding pairs are maximized when W occupies Al sites in B2 TiAl. But when W occupies Al sites in L1(0) TiAl, the W-Ti bonding is weakened by the existence of Al in the alternating (002) plane, which can, however, strengthen the in-plane W-Ti bonding when W occupies Ti sites.
关键词:
gamma-titanium aluminides;electronic-structure;microstructure;deformation;systems;alloys
阳建红
,
董进辉
,
李海斌
,
石强
,
郭明映
复合材料学报
在60℃、80℃相对湿度90%环境条件下对F-12纤维进行了湿热老化实验,研究了长时间老化时纤维吸湿规律.通过ATR-FTIR光谱分析了湿热老化后水对F-12纤维化学结构的影响以及水在纤维中可能存在的方式,探讨了吸湿机制,实验研究了纤维单丝拉伸强度的变化,并采用SEM观察了纤维表面及拉伸断口形貌.结果表明:F-12纤维长时间的吸湿属于2阶段吸湿,吸湿初期符合Fick第二定律,后期偏离,吸湿2500 h后仍没达到平衡;水分子对F-12纤维的化学结构没有造成明显的破坏,老化2500 h后F-12纤维表面变得粗糙,出现了一些沟槽,老化后期断口呈现出脆性与原纤化复合的特征;拉伸断裂强度并非持续减小,而是在起伏波动中减小.
关键词:
F-12纤维
,
吸湿规律
,
ATR-FTIR
,
SEM
,
吸湿机制
,
拉伸强度
杨武
,
陈淼
,
康经武
,
欧庆瑜
,
康敬万
,
高锦章
冶金分析
doi:10.3969/j.issn.1000-7571.1999.05.013
对f-f跃迁光谱在分析化学中的应用进展进行了简要的总结,详细地介绍了根据超灵敏跃迁强度变化规律测定溶液中镧系配合物的组成、形成常数及测定混合稀土中单一稀土的原理和方法.
关键词:
f-f跃迁光谱
,
镧系元素配合物
,
组成测定
,
形成常数
,
综述
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
Journal of Applied Physics
The ternary intermetallic compound Gd3Fe28.2W0.8 with a Nd3Fe29-xTix-type structure was synthesized with W as a stabilizing element, and its crystal structure and magnetic properties were investigated by means of x-ray powder diffraction and magnetic measurements. The space group of Gd3Fe28.2W0.8 is Angstrom 2/m with lattice parameters a=10.5812 Angstrom, b = 8.5338 Angstrom, c = 9.6986 Angstrom, and beta = 96.86 degrees. Rietveld refinement of the crystal structure reveals that W atoms occupy exclusively three crystallographic positions (4g, 4i(3), 4i(4)) with only one neighboring Gd atom. The preferential occupation of W atoms can be understood in terms of the site volume and enthalpy of mixing. The compound exhibits a planar magnetocrystalline anisotropy perpendicular to the [102] direction. The Curie temperature T-c, saturation moment M-s, and anisotropy field H-A are 502 K, 38.6 mu(B)/f.u., and 7.5 T, respectively. (C) 2000 American Institute of Physics. [S0021-8979(00)07520-4].
关键词:
phase;gd;cr;mn
