Y. G .Zhang
,
C. Q. Chen (Beijing University of Aeronautics and Astronautics
,
Beijing 100083
,
China)Q. Xu (Beijing Laboratory of Electron Microscopy
,
Chinese Academy of Sciences. Beijing
,
China)M. C. Chaturvedi (The University of Manitoba
,
Winnipeg
,
Manitoba
,
Canada R3T 2N2)
金属学报(英文版)
A two-phase TiAl-based alloy with fully lamellar structure has been deformed al room temperature and the deformed microstructures have been examined in dtails by optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy(TEM) . Deformation mechanisms in the γ-TiAl phase has been defined and the role of grain boundaries in the deformation and fracture has been assessed Some of the mechanisms of interactions between twinning or gliding dislocations and three types of γ γ domain boundaries or γ α_2 interface in a lamellar grain have been identified and resistance of the various domain boundaries or the interface to the propagation of twinning has been evaluated
关键词:
:TiAl
,
null
,
null
,
null
H.M.Li
,
Z.J.Ding
金属学报(英文版)
A new parallel Monte Carlo simulation method of secondary electron (SE) and backscattered electron images (BSE) of scanning electron microscopy (SEM) for a complex geometric structure has been developed. This paper describes briefly the simulation method and the modification to the conventional sampling method for the step length. Example simulation results have been obtained for several artificial structures.
关键词:
Monte Carlo
,
null
,
null
Mineralogical Magazine
The ultrastructures of parisite-(Ce) from a rare-earth mineral deposit of Sichuan Province, southwest China, have been observed and investigated by selected area electron diffraction (SAED) and high resolution electron microscopy (HREM). Six new polytypes 4H, 10H, 16H, 18R, 24R and 30R were determined in parisite-(Ce), as were their crystal structure types, subcell (a'c''', a'c ", a'c') and supercell (ac) parameters, reflection conditions, polytype features and probable space groups. The HREM studies revealed the complex polytypism in parisite-(Ce) whereby the six new polytypes, formed by long-period ordered stacking, always coexist with the common polytype parisite-(Ce)-6R by syntaxy and thus constitute the complex microstructural 'syntactic polycrystals', the host of which is the polytype parisite-(Ce)-6R.
关键词:
parisite;polytype;high-resolution electron microscopy
Scripta Materialia
An in situ ex-environmental transmission electron microscopy (TEM) study was carried out to investigate the oxidation behavior of RESn(3) (RE = Nd, La, Ce) film in a room at 18 +/- 2 degrees C with 20 +/- 5% humidity. The original RESn(3) compounds transformed into RE(OH)(3) nanocrystals and Sn clusters. This involved the selective oxidation of RE in RESn(3) and the atomic diffusion of Sn atoms. The whole oxidation behavior was discussed from the thermodynamic viewpoint, and a reaction formula was proposed to summarize the oxidation of RESn(3) under different ambient conditions. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
RESn(3) compounds;Oxidation;Thermodynamics;Transmission electron;microscopy (TEM);pb-free solders;whisker growth;tin whiskers;surface;joints;alloys
Philosophical Magazine Letters
In order to reveal the effect of grain boundaries (GBs) on cyclic deformation, the cyclically saturated dislocation patterns within grains and in the vicinity of GBs in a copper bicrystal with a large-angle GB and a copper multicrystal containing small-angle GBs have been observed by the electron channelling contrast technique in scanning electron microscopy. The observations for the multicrystal show that dislocation walls and persistent slip bands (PSBs) can transfer through the small-angle GBs. However, in the copper bicrystal with a large-angle GB perpendicular to the stress axis, PSBs can only form within the component grain with a relatively higher Schmid factor and cannot pass through the GB. From the experimental observations, the effect of GBs on cyclic deformation behaviour is discussed.
关键词:
single-crystals;fatigue
Metallurgical Transactions a-Physical Metallurgy and Materials Science
The influence on the apparent martensitic morphology and substructure of tilting a thin-foil specimen through various angles in the transmission electron microscope was studied in detail. It was found that the amount of laths with internal twins in low-carbon steel after quenching from high temperature is more than 40 pct; the microstructure of medium- and high-carbon steel after quenching from high temperature is completely twinned martensite. Distinguishing twinned martensite by observation of martensitic morphology and substructure using a thin-foil transmission electron microscope seems rather unreliable. Previous reports that the volume fraction of lath martensite is about 100 pct in low-carbon steel and 75 to 90 pct in medium-carbon steel quenched from high temperature perhaps need reassessment. The conditions under which internal twins within martensite could be observed in the transmission electron microscope are also discussed.
关键词:
strength
Acta Metallurgica Et Materialia
In this paper, the Ni and Ti powder mixture with equiatomic ratio was high energy ball milled and then consolidated by explosive compaction. The microstructures of as-compacted and heat treated bulk samples after explosive consolidation are investigated in detail by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). The experiment results reveal the microstructure variation during mechanical alloying in Ni-Ti binary systems. It is found that a metastable phase denoted as I phase formed during ball milling and the structure of I phase was determined by both electron diffraction and HREM. Finally, the mechanism of amorphization induced by ball milling was discussed.
关键词:
cu;amorphization;phases
Journal of Materials Science
High-resolution transmission electron microscopy images of stacking faults on (001) and (<(1)over bar 01>) planes in a beta-Si3N4 whisker were obtained and compared to image simulations. This procedure showed that the atomic structure of the four atomic planes around the (001) stacking fault plane in the beta-phase is very similar to that of the unit cell of alpha-Si3N4 crystal. The stacking fault was observed to climb under electron irradiation in the microscope.
关键词:
silicon-nitride;diffraction;composite;ceramics
