Deformation and Comminution of Shock Loaded α-Al2O3 in the Mescall Zone of Ceramic Armor

1994 ◽  
Vol 362 ◽  
Author(s):  
J. T. Mcginn ◽  
R. W. Klopp ◽  
D. A. Shockey
Keyword(s):  
Fragment Size ◽  
Penetration Resistance ◽  
Deformation And Failure ◽  
Slip Bands ◽  
Transmission Electron ◽  
Loaded Material ◽  
Penetration Behavior ◽  
Α Al2o3 ◽  
Transgranular Cracks ◽  
Explosive Detonation

AbstractIncursion of high density penetrators into ceramic armor is preceded by the formation of a finely comminuted rubble bed at the penetrator tip, the Mescall zone. The deformation and failure processes that result in the Mescall zone are critical to understanding penetration resistance and to modeling penetration behavior. Transmission electron microscopy (TEM) was used to examine shock loaded material in the vicinity of an explosive detonation in α-Al2O3 and to infer the phenomenology of plasticity and fracture occurring at the tip of an advancing penetrator in ceramic armor. Comminution proceeds by intergranular fracture until the fragment size approaches the grain size. Further fragmentation proceeds by transgranular cracks, which nucleate at preexisting microvoids and at intersections of basal twins and primary and secondary slip bands.

Surface Relief Formation in Relation to the Underlying Dislocation Arrangement

2016 ◽  
Vol 258 ◽  
pp. 526-529 ◽  
Author(s):  
Veronika Mazánová ◽  
Milan Heczko ◽  
Ivo Kuběna ◽  
Jaroslav Polák
Keyword(s):  
Electron Microscopy ◽  
Dislocation Structure ◽  
Fatigue Crack Initiation ◽  
Surface Profile ◽  
Specimen Surface ◽  
Slip Bands ◽  
Transmission Electron ◽  
Persistent Slip Bands ◽  
Relief Formation ◽  
Cyclic Slip

Two fatigued materials with f.c.c. lattice, i.e. pure polycrystalline copper and austenitic Sanicro 25 stainless steel, were subjected to the study of the persistent slip markings (PSMs) developed on the surface of the suitably oriented grains. They were observed using scanning electron microscopy (SEM) and thin surface FIB lamellae were prepared and studied by transmission electron microscopy (TEM). The aim was to correlate the specimen surface profile with the underlying internal dislocation structure. The localization of the intensive cyclic slip into persistent slip bands (PSBs) of the material was observed and associated with the PSMs on the specimen surface. Extrusions, intrusions and the dislocation structure appertaining to them were analysed, documented and discussed in relation to the models of fatigue crack initiation.

High-resolution transmission electron microscopic investigations of molybdenum thin films on faceted α-Al2O3

2005 ◽  
Vol 38 (2) ◽  
pp. 260-265 ◽  
Author(s):  
Leonore Wiehl ◽  
Jens Oster ◽  
Michael Huth
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Epitaxial Relationship ◽  
Electron Microscopic ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
High Resolution Images ◽  
Α Al2o3 ◽  
Relationship Of

Epitaxially grown Mo films on a faceted corundum (α-Al2O3)mplane were investigated by transmission electron microscopy. Low- and high-resolution images were taken from a cross-section specimen cut perpendicular to the facets. It was possible to identify unambiguously the crystallographic orientation of these facets and explain the considerable deviation (∼10°) of the experimental interfacet angle, as measured with atomic force microscopy (AFM), from the expected value. For the first time, proof is given for a smooth \{10\bar{1}1\} facet and a curvy facet with orientation near to \{10\bar{1}\bar{2}\}. Moreover, the three-dimensional epitaxial relationship of an Mo film on a faceted corundummsurface was determined.

Plasticity and Microstructure of Irradiated Pd

1998 ◽  
Vol 540 ◽  
Author(s):  
N. Baluc ◽  
Y. Dai ◽  
M. Victoria
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Deformation ◽  
Ambient Temperature ◽  
Tensile Deformation ◽  
Microscopic Level ◽  
Macroscopic Scale ◽  
Slip Bands ◽  
Transmission Electron ◽  
Mev Protons

AbstractSingle crystalline specimens of pure Pd have been irradiated at ambient temperature with 590 MeV protons to doses ranging between 10−4 and 10−1 dpa. Tensile deformation experiments revealed that irradiation induces hardening and embrittlement, while scanning (SEM) and transmission electron microscopy (TEM) observations showed that plastic deformation of specimens irradiated to a dose ≥ 10−2 dpa is strongly localized and yields the creation of slip bands at the macroscopic scale and of defect-free channels at the microscopic level.

In situ x-ray study of the γ- to α-Al2O3 phase transformation during atmospheric pressure oxidation of NiAl(110)

2006 ◽  
Vol 21 (12) ◽  
pp. 3047-3057 ◽  
Author(s):  
A. Vlad ◽  
A. Stierle ◽  
N. Kasper ◽  
H. Dosch ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Oxidation In Air ◽  
Α Al2o3 ◽  
Underlying Substrate

The oxidation in air of NiAl(110) was investigated in the temperature range from 870 °C–1200 °C by in situ x-ray diffraction and transmission electron microscopy. Oxidation at 870 °C and 1 bar oxygen leads to the formation of an epitaxial layer of γ-alumina showing an R30° orientation relationship with respect to the underlying substrate. At oxidation temperatures between 950 °C and 1025 °C, we observed a coexistence of epitaxial γ- and polycrystalline δ-Al2O3. The α-Al2O3 starts to form at 1025 °C and the complete transformation of metastable phases to the stable α-alumina phase takes place at 1100 °C. The fcc-hcp martensitic-like transformation of the initial γ-Al2O3 to epitaxial α-Al2O3 was observed. X-ray diffraction and cross-section transmission electron microscopy proved the existence of a continuous epitaxial α-Al2O3 layer between the substrate and the polycrystalline oxide scale, having a thickness of about 150 nm. The relative orientation relationship between the epitaxial alumina and the underlying substrate was found to be NiAl(110) || α-Al2O3 (0001) and [110] NiAl || [1120].

Effect of Metakaolin-Based Modifier on the Permeability of Concrete Structure in the Marine Environment

2013 ◽  
Vol 438-439 ◽  
pp. 117-120
Author(s):  
Jun Tao Ma ◽  
Liang Yan ◽  
Yu Ping Tong ◽  
Hui Xian Wang
Keyword(s):  
Fly Ash ◽  
Marine Environment ◽  
Concrete Structure ◽  
Chloride Ion ◽  
Penetration Resistance ◽  
Chloride Ion Penetration ◽  
Working Performance ◽  
Electric Flux ◽  
Penetration Behavior ◽  
Strength And Durability

Corrosion of the steel reinforcement in the concrete structure caused by chloride ion penetration becomes more serious in the marine environment. Metakaolin has been widely used in the concrete structure to improve the strength and durability. The combination of metakaolin (MK) and fine fly ash (FA) was studied in the article and the penetration behavior of concrete with various contents of metakaolin-based modifier is investigated. The penetration resistance of concrete was tested in combination of electric flux test. The improving mechanism was studied with mercury intrusion porosimetry analysis (MIP). The experiment results indicate that metakaolin-based modifier improved the penetration resistance of concrete obviously. The combination of fine fly ash weakened the water sucking action of metakaolin and preserved the working performance of concrete. The pore size distribution of concrete containing metakaolin-based modifier has been optimized to improve the microstructure and enhance the penetration resistance of concrete.

Precipitate Structure in an Alumina Dispersion-Strengthened Copper Base Composite Layer

2010 ◽  
Vol 152-153 ◽  
pp. 634-638
Author(s):  
Bao Hong Tian ◽  
Xiao Hong Chen ◽  
Yi Zhang ◽  
Yong Liu
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Composite Layer ◽  
Lattice Parameter ◽  
Interface Structure ◽  
Parameter Mismatch ◽  
Direction Parallel ◽  
Transmission Electron ◽  
The Matrix ◽  
Α Al2o3

A dilute copper alloy of Cu-0.45wt%Al -0.066wt %Y was selected to fabricate nanometer size Al2O3 particles dispersion-hardened composite layer by using aluminizing-internal oxidation technique. The structure and size of the precipitate, interface structure, lattice parameter mismatch and morphology were investigated by means of high resolution transmission electron microscope, analytical transmission electron microscope and image processing by VEC software. Results show that two different size and structure nano-alumina precipitate were identified as α-Al2O3 and γ-Al2O3 respectively during different processing. The precipitates possess semi-coherence or coherence interface structure to matrix with typical loop-loop contrast. The cubic γ-Al2O3 precipitate in certain crystal plane and direction parallel to the matrix。

Substructures in deformed Fe-15 Ni-0.8 C austenite

1984 ◽  
Vol 42 ◽  
pp. 472-473
Author(s):  
Anil K. Sachdev ◽  
M. M. Shea
Keyword(s):  
Electron Microscopy ◽  
Shear Bands ◽  
Strain Rates ◽  
Normal Strain ◽  
Austenite Matrix ◽  
Band Formation ◽  
Slip Bands ◽  
Transmission Electron ◽  
The Common ◽  
Intense Shear

In a recent study, the mechanical behavior of an Fe-15 Ni-0.8 C austenite was determined at various strain rates and temperatures. An important finding of this study was the formation of intense shear bands during deformation at temperatures much greater than which bore no resemblance to the common morphologies of martensites. There is much disagreement in the literature regarding the mechanism of band formation and the associated substructure. These bands have been reported to be fine BCC martensite particles or laths delineating slip bands or thin twins in the austenite matrix. The purpose of the present work was to determine by transmission electron microscopy and diffraction the substructure of the fine bands and to attempt to clarify the various interpretations. For comparison, the substructure produced at a lower deformation temperature was also evaluated where the martensite was known to have the normal strain-induced morphology.

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