Dynamic Evolution of Defect Structures during Spall Failure of Nanocrystalline Al

MRS Advances ◽  
2016 ◽  
Vol 1 (58) ◽  
pp. 3853-3858
Author(s):  
Kathleen Coleman ◽  
Garvit Agarwal ◽  
Avinash M. Dongare
Keyword(s):  
Shock Loading ◽  
Spall Strength ◽  
Dynamic Evolution ◽  
Defect Structures ◽  
Deformation And Failure ◽  
Average Grain Size ◽  
Initial Shock ◽  
Dynamics Simulations ◽  
20 Nm ◽  
Spall Failure

ABSTRACTThe dynamic evolution and interaction of defects under the conditions of shock loading in nanocrystalline Al with an average grain size of 20 nm is investigated using molecular dynamics simulations for an impact velocity of 1 km/s. Four stages of defect evolution are identified during shock deformation and failure that correspond to the initial shock compression (I), the propagation of the compression wave (II), the propagation and interaction of the reflected tensile waves (III), and the nucleation, growth, and coalescence of voids (IV). The results suggest that the spall strength of the nanocrystalline Al system is attributed to a high density of Shockley partials and a slightly lower density of twinning partials (twins) in the material experiencing the peak tensile pressures.

Molecular Dynamics Studies of Spalling and Melting in Shocked Nanocrystalline Pb

2013 ◽  
Vol 577-578 ◽  
pp. 613-616
Author(s):  
Mei Zhen Xiang ◽  
Hai Bo Hu ◽  
Jun Chen
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Tensile Stress ◽  
Grain Boundaries ◽  
Shock Intensity ◽  
Void Growth ◽  
Shock Loading ◽  
Spall Strength ◽  
Boundary Effects ◽  
Dynamics Simulations

The mechanisms of spalling and melting in nanocrystalline Pb under shock loading are studied by molecular dynamics simulations. Our results show that grain boundaries have significant influences on spalling behaviors in cases of classical spallation and releasing melting. In these cases, cavitation and melting both start on grain boundaries, and they display mutual promotion: melting makes the voids nucleate at smaller tensile stress, and void growth speeds melting. Due to grain boundary effects, the spall strength of nanocrystalline Pb varies slowly with the shock intensity in cases of classical spallation. In cases of releasing melting and compression melting, spall strength of both single-crystalline and nanocrystalline Pb drops dramatically as shock intensity increases.

ATOMIC FORCE MICROSCOPY AND XRD ANALYSIS OF SILVER FILMS DEPOSITED BY THERMAL EVAPORATION

2006 ◽  
Vol 20 (02) ◽  
pp. 217-231 ◽  
Author(s):  
MUHAMMAD MAQBOOL ◽  
TAHIRZEB KHAN
Keyword(s):  
Atomic Force Microscopy ◽  
Grain Size ◽  
Surface Characterization ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Xrd Analysis ◽  
Force Microscopy ◽  
Atomic Force ◽  
Average Grain Size ◽  
20 Nm

Thin films of pure silver were deposited on glass substrate by thermal evaporation process at room temperature. Surface characterization of the films was performed using X-ray diffraction (XRD) and atomic force microscopy (AFM). Thickness of the films varied between 20 nm and 72.8 nm. XRD analysis provided a sharp peak at 38.75° from silver. These results indicated that the films deposited on glass substrates at room temperature are crystalline. Three-dimension and top view pictures of the films were obtained by AFM to study the grain size and its dependency on various factors. Average grain size increased with the thickness of the deposited films. A minimum grain size of 8 nm was obtained for 20 nm thick films, reaching 41.9 nm when the film size reaches 60 nm. Grain size was calculated from the information provided by the XRD spectrum and averaging method. We could not find any sequential variation in the grain size with the growth rate.

Transport Properties of B-, P-Doped and Undoped 50 kHz PECVD Microcrystalline Silicon

1989 ◽  
Vol 164 ◽  
Author(s):  
M.A. Hachicha ◽  
Etienne Bustarret
Keyword(s):  
Grain Size ◽  
Hall Mobility ◽  
Solid Phase ◽  
Grazing Angle ◽  
Dc Conductivity ◽  
X Ray Diffraction ◽  
Crystalline Fraction ◽  
Average Grain Size ◽  
20 Nm ◽  
Solid Phase Density

AbstractUndoped 500 nm-thick silicon layers with a crystalline fraction around 95% and an average grain size of 20 nm have been deposited at 350°C by 50 kHz triode PECVD in a H2/SiH4 mixture, in the presence of a magnetic field. Their room temperature (rt) dc conductivity μrt is 0.03 Δ−1cm−1 for a Hall mobility of 0.8 cm 2V−1s−1.The study by SIMS, infrared absorption, grazing angle x-ray diffraction and Raman scattering spectroscopies of the doped samples shows how the crystalline fraction and the grain size drop as the B2H6/SiH4 and PH3/SiH4 volumic ratios increase from 10 ppm to 1%.The rt dc conductivity reaches 2 Δ−1 cm−1 (Hall mobility: 15 cm2V−ls−1) for a solid phase density of 1019 cm−3 boron atoms, and 30 Δ−1cm−1 (Hall mobility: 55 cm2V−ls−1) at the maximum P incorporation of 8 × 1020cm−3.

scholarly journals Investigation of Primary Recrystallization and Decarbonization with Different Heating Rates of Intermediate Annealing Using Nb-Containing Grain-Oriented Silicon Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1655
Author(s):  
Xin Tian ◽  
Shuang Kuang ◽  
Jie Li ◽  
Jing Guo ◽  
Yunli Feng
Keyword(s):  
Heating Rate ◽  
Electron Backscatter Diffraction ◽  
Optical Microscope ◽  
Primary Recrystallization ◽  
Silicon Steel ◽  
Intermediate Annealing ◽  
Heating Rates ◽  
Average Grain Size ◽  
The Matrix ◽  
20 Nm

An Nb-containing grain-oriented silicon steel was produced through double-stage cold rolling in order to investigate the effect of the heating rate during intermediate annealing on primary recrystallization and decarburization behavior. The microstructure and texture were observed and analyzed by an optical microscope and an electron backscatter diffraction system. A transmission electron microscope was used to observe the precipitation behavior of inhibitors. The decarburization effect during intermediate annealing was also calculated and discussed. The results show that primary recrystallization takes place after intermediate annealing. As the heating rate increases, the average grain size decreases gradually. The textures of {411}<148> and {111}<112> were found to be the strongest along the thickness direction in all of the annealed specimens and are mainly surrounded by HEGB and HAGB (> 45°). A large number of inhibitors with the size of 14~20 nm precipitate are distributed evenly in the matrix. The above results indicate that the higher heating rate during intermediate annealing contributes to both an excellent microstructure and magnetic properties. From the calculation, as the heating rate increases, decarbonization tends to proceed in the insulation stage, and the total amount of carbonization declines.

Size Effect in Plastic Deformation and Failure of Metallic Glasses

2020 ◽  
Vol 405 ◽  
pp. 212-216
Author(s):  
Jozef Miškuf ◽  
Kornel Csach ◽  
Alena Juríková ◽  
Mária Demčáková ◽  
Mária Demčáková ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Metallic Glasses ◽  
High Strength ◽  
Dimple Size ◽  
Deformation And Failure ◽  
Composition And Structure ◽  
Instantaneous Deformation ◽  
20 Nm ◽  
Short Time ◽  
Stored Elastic Energy

Depending on the composition and structure of metallic glasses cells with the dimensions in the range from tenths nanometers to tenths micrometers were observed on the ductile fracture surface. The variation in dimple size was compared with the serrations presented on the loading curve at the nanoindentation of the metallic glasses with different compositions. Higher instantaneous deformation can be connected with simultaneous shearing at more suitable shear band configurations. The cell morphology with the various cell sizes is observed at the failure of the metallic glasses. At the failure of high strength metallic glasses, the cells are formed in short time due to the release of high amount of stored elastic energy. In this case the uniform cell morphology with the cell size of about 20 nm is observed.

AlSb THIN FILMS PREPARED BY DC MAGNETRON SPUTTERING AND ANNEALING

2008 ◽  
Vol 22 (14) ◽  
pp. 2275-2283 ◽  
Author(s):  
WEIDONG CHEN ◽  
LIANGHUAN FENG ◽  
ZHI LEI ◽  
JINGQUAN ZHANG ◽  
FEFE YAO ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
High Efficiency ◽  
Dark Conductivity ◽  
Aluminum Antimonide ◽  
Dc Magnetron Sputtering ◽  
Glass Substrates ◽  
Average Grain Size ◽  
P Type ◽  
20 Nm

Aluminum antimonide (AlSb) is thought to be a potential material for high efficiency solar cells. In this paper, AlSb thin films have been fabricated by DC magnetron sputtering on glass substrates. The sputtering target consists of aluminum and antimony, and the area ratio of Al to Sb is 7:3, which is derived from research into the relationship between the deposition rates of both the metals and sputtering power. XRD and AFM measurements show that the as-deposited films are amorphous, but become polycrystalline with an average grain size of about 20 nm after annealing in an argon atmosphere. From optical absorption measurements of annealed AlSb films, a band gap of 1.56 eV has been demonstrated. Hall measurements show that the films are p-type semiconductors. The temperature dependence of dark conductivity tested in vacuum displays a linear lnσ to 1/T curve, which indicates a conductivity activation energy of around 0.61 eV.

Investigation into the Spall Strength of Cast Iron

2012 ◽  
Vol 13 (2) ◽  
pp. 195-199
Author(s):  
Gifford Plume ◽  
Carl-Ernst Rousseau
Keyword(s):  
Cast Iron ◽  
Spall Strength ◽  
Peak Stress ◽  
Small Scale ◽  
Spall Fracture ◽  
Gas Gun ◽  
Minimum Stress ◽  
Impact Experiments ◽  
Insight Into ◽  
Spall Failure

Abstract The spall strength of cast iron has been investigated by means of planar plate impact experiments conducted in a vacuum. A single stage gas gun was utilized to drive projectiles to velocities between 100 and 300 m/sec, resulting in low to moderate shock loading of the cast iron specimens. Measurement of the stress histories were made with the use of commercial manganin stress gauges that were imbedded between the back face of the cast iron specimen and a low impedance backing of polycarbonate. Spall strength values were calculated utilizing the measured peak stress and minimum stress pullback signals captured in the stress history. Spall Strength values were found to vary between 0.98 and 1.45 GPa for the cast iron tested. Post-Mortem analysis of recovered specimen has provided insight into the evolution of spall failure in cast iron and shed light on the varying nature of the spall strength values calculated. It was determined that the lower bound of strength values was associated with small scale micro-failure, while the upper bound values corresponded to complete spall fracture.

Molecular dynamics simulations of shock loading of nearly fully dense granular Ni–Al composites

2019 ◽  
Vol 21 (36) ◽  
pp. 20252-20261
Author(s):  
Yongnan Xiong ◽  
Xiaofan Li ◽  
Shifang Xiao ◽  
Huiqiu Deng ◽  
Bowen Huang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Chemical Reaction ◽  
Shock Loading ◽  
Shock Propagation ◽  
Inhomogeneous Deformation ◽  
Reaction Characteristics ◽  
Dynamics Simulations

We used molecular dynamics simulations to study the shock propagation, inhomogeneous deformation, and initiation of the chemical reaction characteristics of nearly fully dense reactive Ni–Al composites.

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