Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

The changes of the phase composition, structure and physicomechanical properties of Ti‑40 mas % Nb after severe plastic deformation are investigated in this paper. By the methods of microstructural, X-ray diffraction analysis and scanning electron microscopy it is determined that phase and structural transformations occur simultaneously in the alloy after severe plastic deformation. The martensitic structure formed after tempering disappears. The inverse α'' → β transformation occurs. The structure consisting of oriented refined grains is formed. The alloy is hardened due to the cold working. The Young modulus is equal to 79 GPa and it is less than that of initial alloy and close to the value obtained after tempering. It is possible that Young modulus is reduced by additional annealing.

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The generation of dislocations during cleavage

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1957.0182 ◽

1957 ◽

Vol 242 (1230) ◽

pp. 392-399 ◽

Cited By ~ 22

Keyword(s):

Plastic Deformation ◽

Lithium Fluoride ◽

Fatigue Cracks ◽

Important Application ◽

Cleavage Crack ◽

Time Estimate ◽

Moving Crack ◽

Perfect Cleavage ◽

Fluoride Crystals ◽

Opening And Closing

A cleavage crack can generate plastic deformation in a crystal only if it is moving sufficiently slowly or can be brought to rest. This can be demonstrated very strikingly by the cleavage of rock salt or lithium fluoride crystals at a low rate of loading. The cleavage crack propagates discontinuously under these conditions, and thus provides a range of velocities at which deformation might occur. It is found that intense plastic deformation occurs only in narrow zones around the positions where the crack stops; elsewhere the crack runs freely producing a perfect cleavage. It is possible to detect and at the same time estimate the magnitude of this deformation by studying the interference pattern produced by light reflected from the two surfaces of the crack. Observations of this kind allow the deformation to be interpreted as the production of arrays of loops of dislocation by the slowly moving crack. The interference technique is also valuable for displaying the presence of the crack so that its mode of propagation can be studied. A number of observations of the opening and closing of cracks suggest that a study of this kind using a system of reversed stressing might have an important application to the problems of the propagation of fatigue cracks.

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Texture Development in a Model Al-Li Alloy Subjected to Severe Plastic Deformation

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.114.337 ◽

2006 ◽

Vol 114 ◽

pp. 337-344 ◽

Cited By ~ 2

Author(s):

Bogusława Adamczyk-Cieślak ◽

Jaroslaw Mizera ◽

Krzysztof Jan Kurzydlowski

Keyword(s):

Plastic Deformation ◽

Severe Plastic Deformation ◽

Equal Channel Angular Extrusion ◽

Orientation Distribution ◽

X Ray Diffraction ◽

Technological Parameters ◽

Initial State ◽

Texture Characteristic ◽

X Ray ◽

Ultrafine Grained

The texture of Al – 0.7 wt. % Li alloy processed by two different methods of severe plastic deformation (SPD) has been investigated by X-ray diffraction, and analyzed in terms of the orientation distribution function (ODF). It was found that severe plastic deformation by both Equal Channel Angular extrusion (ECAE) and Hydrostatic Extrusion (HE) resulted in an ultrafine grained structure in an Al – 0.7 wt. % Li alloy. The microstructure, grain shape and size, of materials produced by SPD strongly depend on the technological parameters and methods applied. The texture of the investigated alloy differed because of the different modes of deformation. In the initial state the alloy exhibited a very strong texture consisting of {111} fibre component. A similar fibrous texture characteristic was also found after HE whereas after the ECAE the initial texture was completely changed.

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Real-Time Composition And Thickness Control Techniques In A Metalorganic Chemical Vapor Deposition Process

MRS Proceedings ◽

10.1557/proc-406-133 ◽

1995 ◽

Vol 406 ◽

Author(s):

M. S. Gaffneyt ◽

C. M. Reavesl ◽

A. L Holmes ◽

R. S. Smith ◽

S. P. DenBaars

Keyword(s):

Chemical Vapor Deposition ◽

Real Time ◽

Vapor Deposition ◽

Metalorganic Chemical Vapor Deposition ◽

Chemical Vapor ◽

Normal Operation ◽

Growth Monitoring ◽

X Ray Diffraction ◽

X Ray ◽

Metalorganic Chemical

AbstractMetalorganic chemical vapor deposition (MOCVD) is a process used to manufacture electronic and optoelectronic devices that has traditionally lacked real-time growth monitoring and control. We have developed control strategies that incorporate monitors as real-time control sensors to improve MOCVD growth. An analog control system with an ultrasonic concentration monitor was used to reject bubbler concentration disturbances which exist under normal operation, during the growth of a four-period GaInAs/InP superlattice. Using X-ray diffraction, it was determined that the normally occurring concentration variations led to a wider GaInAs peak in the uncompensated growths as compared to the compensated growths, indicating that closed loop control improved GaInAs composition regulation. In further analysis of the X-ray diffraction curves, superlattice peaks were used as a measure of high crystalline quality. The compensated curve clearly displayed eight orders of satellite peaks, whereas the uncompensated curve shows little evidence of satellite peaks.

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