A combined TEM and SEM study of erosive wear

Author(s):  
T.H. Kosel ◽  
R.O. Scattergood ◽  
A.P.L. Turner

Mechanisms of erosive wear are being studied using transmission electron microscopy (TEM) to examine the subsurface dislocation structures developed and scanning electron microscopy (SEM) to observe the surface topography. Specimens of recrystallized Ni 200 and copper single crystals have been eroded with 5 to 25μm glass microbeads and with 40 and 150 μm A12O3 particles at 53 m/sec using a slinger type erosion apparatus. Thin foils parallel to the original rough eroded surface and one μm or more below it have been prepared by first electroplating a few microns of nickel on the specimen and then electropolishing it away. Thin foil sections at 45̊ to the original surface have been prepared by sectioning specimens with thick electroplated layers; these allow observations to be made at different depths in the same foil.Material removal during particle impingement erosion at low angles of incidence probably occurs by a cutting or micromachining mechanism similar to that suggested by Finnie (1).

2017 ◽  
Vol 50 (4) ◽  
pp. 1028-1035 ◽  
Author(s):  
Hongbing Yu ◽  
Zhongwen Yao ◽  
Fei Long ◽  
Peyman Saidi ◽  
Mark R. Daymond

This study reportsin situobservations of the formation of the δ′-ZrO phase, occurring during the annealing of transmission electron microscopy (TEM) thin foils of both pure Zr and a Zr–Sn–Nb–Mo alloy at 973 K in a transmission electron microsope. The lattice parameters of δ′-ZrO were measured and determined to be similar to those of the ω-Zr phase. The orientation relationship between the δ′-ZrO and α-Zr phases has been identified as either {(11 \overline{2}0)}_{\rm ZrO}//{(0002)}_{\alpha} and {[0002]}_{\rm ZrO}//{[11 \overline{2}0]}_{\alpha} or {(\overline{1}011)}_{\rm ZrO}//{(0002)}_{\alpha} and {[01{\overline 1}1]_{{\rm{ZrO}}}}//{[11{\overline 2}0]_\alpha} depending on the orientation of the α grain relative to the TEM thin-foil normal. The nucleation and growth of δ′-ZrO were dynamically observed. This study suggests a new and convenient way to study oxidation mechanisms in Zr alloys and provides a deeper understanding of the properties of the newly reported δ′-ZrO. Since δ′-ZrO has a Zr sublattice which is identical to that of ω-Zr, the orientation relationships between the α and δ′-ZrO phases may also shed light on the orientation relations existing between α- and ω-Zr, and hence α- and ω-Ti.


Author(s):  
G.J.C. Carpenter ◽  
J.A. Jackman ◽  
J. McCaffrey

Argon ion sputtering is widely used in the final thinning stage for the preparation of thin foils for transmission electron microscopy. During a recent study of a titanium alloy, we observed that ion-beam thinning resulted in specimens that appeared in the electron microscope to have become severely damaged. Similar microstructures had been observed previously in zirconium, thinned in this manner. Because ion-beam sputtering takes place on the atomic scale, it seemed unlikely that gross distortion of a thin foil could have been caused directly by the sputtering process. A more detailed study has therefore been made of this phenomenon.


1991 ◽  
Vol 246 ◽  
Author(s):  
Tsugio Tadaki ◽  
Sukeyoshi Yamamoto ◽  
Ken'ichi Shimizu

AbstractA peculiar martensite found in thin foils of a Ti5oNi49Fei shape memory alloy has been examined by transmission electron microscopy and electron diffraction, which was entirely different from the R phase and the B19' and B19 martensites widely known so far in the Ti-Ni based alloys. The thin foil martensite is monoclinic with a=0.700nm, b=0.994nm, c=0.632nm and γ =94.4°. The lattice correspondence between the B2 parent phase and the martensite is as follows: <210>B2→ <100>M, <230>B2→ <010>m, <002>B2→ <001>m. The formation conditions and atom positions in the unit cell of the thin foil martensite are discussed.


Author(s):  
E. U. Lee ◽  
P. A. Garner ◽  
J. S. Owens

Evidence for ordering (1-6) of interstitial impurities (O and C) has been obtained in b.c.c. metals, such as niobium and tantalum. In this paper we report the atomic and microstructural changes in an oxygenated c.p.h. metal (alpha titanium) as observed by transmission electron microscopy and diffraction.Oxygen was introduced into zone-refined iodide titanium sheets of 0.005 in. thickness in an atmosphere of oxygen and argon at 650°C, homogenized at 800°C and furnace-cooled in argon. Subsequently, thin foils were prepared by electrolytic polishing and examined in a JEM-7 electron microscope, operated at 100 KV.


Author(s):  
W. D. Cooper ◽  
C. S. Hartley ◽  
J. J. Hren

Interpretation of electron microscope images of crystalline lattice defects can be greatly aided by computer simulation of theoretical contrast from continuum models of such defects in thin foils. Several computer programs exist at the present time, but none are sufficiently general to permit their use as an aid in the identification of the range of defect types encountered in electron microscopy. This paper presents progress in the development of a more general computer program for this purpose which eliminates a number of restrictions contained in other programs. In particular, the program permits a variety of foil geometries and defect types to be simulated.The conventional approximation of non-interacting columns is employed for evaluation of the two-beam dynamical scattering equations by a piecewise solution of the Howie-Whelan equations.


2009 ◽  
Vol 24 (3) ◽  
pp. 647-651 ◽  
Author(s):  
M. Rester ◽  
C. Motz ◽  
R. Pippan

Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analyses of small indentations in copper single crystals exhibit only slight changes of the crystal orientation in the surroundings of the imprints. Far-reaching dislocations might be the reason for these small misorientation changes. Using EBSD and TEM technique, this work makes an attempt to visualize the far-propagating dislocations by introducing a twin boundary in the vicinity of small indentations. Because dislocations piled up at the twin boundary produce a misorientation gradient, the otherwise far-propagating dislocations can be detected.


2007 ◽  
Vol 1026 ◽  
Author(s):  
Pascale Bayle-Guillemaud ◽  
Aurelien Masseboeuf ◽  
Fabien Cheynis ◽  
Jean-Christophe Toussaint ◽  
Olivier Fruchart ◽  
...  

AbstractThis paper presents investigations of magnetization configuration evolution during in-situ magnetic processes in materials exhibiting planar and perpendicular magnetic anisotropy. Transmission electron microscopy has been used to perform magnetic imaging. Fresnel contrasts in Lorentz Transmission Electron Microscopy (LTEM) and phase retrieval methods such as Transport of Intensity Equation (TIE) solving or electron holography have been implemented. These techniques are sensitive to magnetic induction perpendicular to the electron beam and can give access to a spatially resolved (resolution better than 10 nm) mapping of magnetic induction distribution and could be extended to dynamical studies during in-situ observation. Thin foils of FePd alloys with a strong perpendicular magnetic anisotropy (PMA) and self-assembled Fe dots are presented. Both are studied during magnetization processes exhibiting the capacities of in-situ magnetic imaging in a TEM.


2016 ◽  
Vol 874 ◽  
pp. 323-327
Author(s):  
Hong Xiu Zhou ◽  
Ming Lei Li ◽  
Neng Dong Duan ◽  
Bo Wang ◽  
Zhi Feng Shi ◽  
...  

A nanotwinned surface is formed on a titanium alloy under nanoindentations. Prior to nanoindentation, blocks of a ternary titanium alloy are machined by chemical mechanical polishing. The surface roughness Ra and peak-to-valley values are 1.135 nm and 8.82 nm, respectively. The hardness in the indented surface is greatly increased, indicated from the load-displacement curves compared to the polished surfaces. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is uniformly generated by nanoindentations at room temperature, which is different from previous findings, in which high temperature, high pressure, or chemical reagents are usually used. The nanotwinned surface is produced by pure mechanical stress, neither material removal nor addition.


2005 ◽  
Vol 899 ◽  
Author(s):  
Yoosuf Picard ◽  
Steven M. Yalisove

AbstractPre-thinned foils composed of amorphous silicon and polycrystalline cobalt were irradiated using femtosecond pulse-length lasers at fluences sufficient for ablation (material removal). The resultant ablated hole and surrounding vicinity was studied using transmission electron microscopy to determine modifications to the structure. Evidence of cobalt silicide formation was observed within a 3 micron radius of the laser hole edge by use of selected area electron diffraction (SAED). In addition, elongated grains of crystalline silicon was observed within 500 nm of the laser hole edge, indicating melting of the amorphous silicon and heat dissipation slow enough to allow recyrstallization. This initial work demonstrates the use of pre-designed nanostructured multilayer systems as a method for nanoscale profiling of heat dissipation following pulsed laser irradiation.


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