Y.H.Wen 1)
,
N.Li 1)
,
Y.G.Xu 1)
,
M.J.Tu 1)
,
P.Q.Li 2)
,
Y.L.Liu 2) and Y.L.Ma 2) 1) Department of Materials Shaping and Controlling Engineering
,
Sichuan University
,
Chengdu 610065
,
China 2) Xi'an Petroleum Pipe Research Institute
,
Xi'an 710065
,
China
金属学报(英文版)
The effects of quenching temperature on shape memory effect and microstructure of Fe 18Mn 5Si 8Cr 4Ni shape memory alloy have been studied. The results show that both the shape recovery ratio and the recovery strain increased as quenching temperature increased, the amount of stress induced ε martensite in the process of cold work decreased with the increase of quenching temperature, the shape recovery ratio and the recovery strain reached maximum at 650℃, and then decreased rapidly with the further increase of quenching temperature,the stress induced ε martensite wholly disappeared at 1023K. But when the quenching temperature is higher than 1023K, the further increase of quenching temperature had little effect on shape recovery ratio, the amount and size of thermal induced ε martensite would increased with the further increase in quenching temperature. The shape memory effect can be improved by the moderate amount of pre exist ε martensite in the matrix before deforming.
关键词:
shape memory alloy
,
null
,
null
Journal of Alloys and Compounds
The bonding characteristics of A(3)B L1(2) intermetallics have been studied by the discrete variational X(alpha) cluster method. Two concepts, i.e. similarity of bonding strength and delocalization of bonding electrons, are introduced to explain the ductility or brittleness of the materials. The analysis of bonding characteristics shows that the strength of the A-A bond is similar to that of the A-B bond in A(3)B L1(2) intermetallics, and the delocalized degree of bonding electrons is different between the ductile and brittle intermetallics. This is a dominant factor in governing the ductile/brittle behavior of the materials. Environmental embrittlement in some intermetallics is related to the reactive centers in grain boundaries, which is due to the directional bonding and a small amount of charge transfer, and the reactive centers weaken the ability against the attack of the environmental species. The effect of stoichiometry on ductility contributes to the degree of delocalized bonding electrons. Mechanical strength of the materials is correlated with the covalent bond strength.
关键词:
intermetallics;mechanical properties;bond strength calculations;intergranular hydrogen embrittlement;grain-boundary strength;ll2;ordered alloys;environmental embrittlement;fracture;ductility;co3ti
Nabil S. Youssef
,
K.H.Hegab
材料科学技术（英文）
Some transition metal chelates of two ligands L1 and L2 were prepared and characterized by elemental analysis. The IR and 1H NMR spectra of several chelates of two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 showed the involvement of the azo group in chelation with the transition metal ions, in most of the studied chelates, and that the two ligands L1 and L2 were coordinated either in the enol or the keto form. IR spetra also showed that Fe(III)-, Ni(II)-, Mn(II)-, VO(II)-L1 and Cu(II)-L2 chelates behaved in a bidentate manner, in contrast with the two (1:1) M:L cobalt chelates with the two ligands are tridentate. TG analysis indicated the presence of three to twelve water molecules of hydration eliminated on heating up to 150°C and one or two coordinated water molecules removed at 150-180°C. The octahedral structure is proposed for all the chelates, except Cu(II)-L2 and Ni(II)-L1 chelates which have square planar geometry, based on their electronic spectra.
关键词:
Gengxiang HU
,
Shipu CHEN
,
Xiaohua WU
,
Yonghua RONG and Xiaofu CHEN(Dept. of Materials Science
,
Shanghai Jiao Tong University
,
Shanghai
,
200030
,
China)
材料科学技术（英文）
The deformation behaviour and the nature of dislocations of the Al3Ti-base L12 alloya modified with Fe and Mn etc, were investigated. The results show that the deformation and fracture character istics are closely related to the alloy compositions. The effect of hot-working process on the room tem perature ductility is remarkable, not only resulting in an appreciable improvement of compressive properties but also showing a 0.28% plastic strain in tensile test. The SISF dissociation of a < 110>dislocations on {111} planes was found at room temperature. The determined dissociation scheme is consistent with the mechanical behaviour of these alloys in the lower temperature region.
关键词:
王秋艳
,
徐连义
,
付煜
,
张艳丽
,
谢嫚
稀有金属材料与工程
采用低温共沉淀-水热-煅烧法合成了锂离子电池Fe-Ni-Mn体系正极材料Li1+x(Fey/2Niy/2Mn1-y)1-xO2,并用XRD、SEM、ICP光谱和电化学性能测试对材料进行了表征.XRD测试和ICP分析表明,Fe、Ni取代Li2MnO3中的部分Mn,形成很好的固溶结构yLiFe1/2Ni1/2O2-(1-y)Li2MnO3 (y=0.l,0.2,0.3,0.4,0.5).SEM测试表明,取代量y不同,材料的表观形貌有所不同,y=0.4时材料的颗粒粒径均匀、较小,呈类球形结构.电化学性能测试表明,当y=0.4时,循环稳定性最好,充放电50次后放电比容量仍可维持在195.0 mAh/g,放电中值电压为3.5 V,y=0.4时样品在大倍率放电下的电化学性能表现良好.
关键词:
锂离子电池
,
正极材料
,
Li1+x(Fey/2Niy/2Mn1-y)1-xO2
,
离子掺杂
张清
,
李全安
,
井晓天
,
张兴渊
材料工程
doi:10.3969/j.issn.1001-4381.2011.03.016
Mg24Y5相的细化是进一步提高Mg-l0Y合金力学性能的关键.研究了稀土元素sm对Mg-l0Y合金中的Mg24Y5相及其基体组织的细化作用,结果表明:sm的加人,改善了Mg24Y5相的形貌,促进了细小弥散分布的Mg24Y5颗粒相的形成;同时,Sm的加人,通过固溶作用,进一步细化了基体组织;显微组织的改善导致了合金高温下力学性能的提高.
关键词:
Sm
,
Mg-10Y合金
,
组织细化
,
力学性能
Journal of Solid State Chemistry
A serial of samples in Y2O3-Ga2O3-Tm2O3 pseudo-ternary system are prepared by solid-state chemical reaction method. The range of solid solution in (Y1-xTmx)(3)GaO6 is 0 < x < 0.384. Powder X-ray diffraction shows that the compounds crystallize in Gd3GaO6 (Cmc2(1))-type structure. The solid solubilities of Y3+xGa5-xO12 (x = 0-0.77) and Tm3+xGa5-xO12 (x = 0-0.62) are 37.5-47.11 at% Y2O3, and 37.5-45.26 at% Tm2O3, respectively. PL spectra of Tm-doped Y3GaO6 show that there is a sharp blue emission at similar to 456 nm from the D-1(2) -> F-3(4) transition at room temperatures with two lifetimes (similar to 5 and similar to 15 mu s) and a narrow saturation range of PL intensity for the Tm3+ content from x = 0.005 to 0.03. The sharp emission and long lifetime of (Y1-xTmx)(3)GaO6 indicate that Y3GaO6 is a potential phosphor and laser crystal host material. (c) 2005 Elsevier Inc. All rights reserved.
关键词:
Tm3+ -doped Y3GaO6;Y2O3-Ga2O3-Tm2O3 system;(Y1-xTmx)(3)Ga5O12 solid;solution;luminescence;crystal-structure;luminescence;phosphor;cations;ions;tb3
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
