LI Gang
,
WANG Zhongguang
,
LI Guangyi(State Key Laboratory of Fatigue and Fracture for Materials
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)V.OVCHARENKO(Institute of Strength Physics and Materials Science
,
Russian Academy of Science
,
Siberian Branch
,
Tomsk
,
Russia) Manuscript received 3 May 1995
金属学报(英文版)
Self propagating high temperature synthesis(SHS) under compression was utilized to obtain an intermetallic compound Ni_3 Al by using elemental powders.The microstructure of the SHS product was observed by optical microscopy(OM) and scanning electron microscopy(SEM).The results reveal that the SHS Ni3Al is a single-phase polycrystalline alloy wilh LI2 crystal structure.Tensile tests were conducted from room temperature to 800℃ both in air and in vacuum.The results show that the SHS Ni_3Al exhibits an anomalous temperature dependence of ultimate tensile strength.The ultimate tensile strength in vacuum is much higher than that in air over the whole temperature range.Fracture surfaces are characterized by the brittle grain boundary fracture and the intergranular fracture mode can not be affected markedly by the test environment.
关键词:
:Ni_3Al
,
null
,
null
,
null
Philosophical Magazine Letters
Charge-ordered Pr(0.5)Ca(0.5)MnO(3) (PCMO) thin films epitaxially grown on SrTiO(3) (100) substrates were prepared by a two-step growth technique which resulted in a 10 nm thick first layer and a 70 nm thick main layer. The dislocations in the as-received films were investigated using conventional and high-resolution transmission electron microscopy. Pure-edge misfit dislocations with Burgers vectors a < 011 > and line directions < 100 > were found to be the major interfacial defects responsible for the full misfit relief in the PCMO films. These dislocations constitute a square grid of dislocation lines parallel to the PCMO/SrTiO(3) interface. In contrast, two types of dislocations were identified within the first layer. One is of edge type with Burgers vectors a < 110 > and line directions < 001 >; the other, of screw type with Burgers vectors a < 110 > and line directions < 110 >. Cross-slip of the latter may contribute to the multiplication of misfit dislocations necessary for a total misfit relaxation. Few threading dislocations were observed in the main layer. The dislocation configurations in the films are discussed in detail.
关键词:
dislocations;transmission electron microscopy;thin films;perovskites;misfit relaxation mechanisms;moire fringe contrast;magnetic-field;domain configurations;strain;srtio3;interface;substrate;identification;accommodation
L.L.Wang
,
L.H.Zhao
,
W.Y.Hu
,
X.L.Shu
,
X.J.Yuan
,
B.W.Zhang and X.Sheng Department of Applied Physics
,
Hunan University
,
Changsha 410082
,
China
金属学报(英文版)
Manuscript received 24 June 1999 The Fe Al P alloy deposits were plated on copper sheets by electroless plating. The change law of the deposition rate, composition, surface appearance and structure for the deposits was studied by changing the metallic salt ratios (AlCl 3/AlCl 3+FeSO 4), the concentration of metallic salt AlCl 3 and reductant NaH 2PO 2. The optimum plating bath was obtained. It was found that the choices of ligand and reductant were the key of increasing Al content for the deposits.
关键词:
electroless Fe Al P plating
,
null
,
null
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Acta Materialia
An analytical relationship between the ratio of hardness to reduced modulus H/E-r and the geometry of a residual indent is established based on the theories of depth-sensing indentation. Various material parameters, including elastic parameters, recovery deformation and energy-dissipation capacity, are uniquely determined by the value of H/E-r, so that they can be estimated from a residual indent trail. Thus, we are able to know what has happened in the material simply by analyzing or comparing residual trails on the material. The validity of this method has been confirmed by analyzing residual Vickers indents on quasi-plastic ceramic and brittle glass. In addition, it is demonstrated that the geometric constant epsilon in traditional nanoindentation theories is related to the proportional factor eta through the exponent of unloading curve m, i.e., epsilon = m (.) eta, where eta is defined by h(s) = eta (.) (h(m) - h(f)). (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
residual indent;Vickers indenter;property prediction;H/E-r ratio;depth-sensing indentation;instrumented indentation;mechanical-properties;nanoindentation;modulus;hardness;deformation;films;load;substrate
