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Full-Text Articles in Physics

An Electron Channeling Study Of Polycrystalline Yba2cu3ox, J. D. Verhoeven, E. D. Gibson, L. Scott Chumbley, R. William Mccallum, H. H. Baker Jul 1988

An Electron Channeling Study Of Polycrystalline Yba2cu3ox, J. D. Verhoeven, E. D. Gibson, L. Scott Chumbley, R. William Mccallum, H. H. Baker

Materials Science and Engineering Publications

An electron channeling study has been done on large grained YBa2Cu3Ox samples. Selected area channeling patterns (SACP) were used to examine several dozen grains on electropolished surfaces and it was demonstrated that (a) the twin planes observed in polarized optical light microscopy lie parallel to {110} crystal planes, and (b) the long flat sides of high aspect ratio grains are formed by basal planes, and the shorter sides are formed by either (010), (100), or {110} planes. A majority of the large grains examined were found to contain subgrains, misaligned by 0.5°–1° and ...


Possible Twin-Boundary Effect Upon The Properties Of High-Tc Superconductors, M. M. Fang, Vladimir G. Kogan, Douglas K. Finnemore, J. R. Clem, L. Scott Chumbley, D. K. Farrell Feb 1988

Possible Twin-Boundary Effect Upon The Properties Of High-Tc Superconductors, M. M. Fang, Vladimir G. Kogan, Douglas K. Finnemore, J. R. Clem, L. Scott Chumbley, D. K. Farrell

Materials Science and Engineering Publications

We have studied the field at which superconductivity nucleates in grain-aligned samples of Y1Ba2Cu3O7-δ very close to the transition temperature Tc. For the field parallel to the c axis and for temperatures within 2 K of Tc, the nucleation field is found to vary as (1-T/Tc)1/2. The data suggest that superconductivity localized near twin boundaries may exist at temperatures close to Tc. .AE


A Study Of Strain-Induced Phase Transformations In Tini Alloy By Electric Resistance Method, Yuan-Ti Muang, Li-Lin Lu, Lai-Zhi Zou, Wang-Yu You Jan 1988

A Study Of Strain-Induced Phase Transformations In Tini Alloy By Electric Resistance Method, Yuan-Ti Muang, Li-Lin Lu, Lai-Zhi Zou, Wang-Yu You

Review of Progress in Quantitative Nondestructive Evaluation

It is generally recognized that the shape memory effect (SME) is associated the interaction of stress with thermoelastic martensitic transformation [1]. The phase transformations in TiNi alloy was reported to occur as three kinds of B2→R, B2→M, R→M phase transformations [2]. There are different views about premartensitic transformation in TiNi based alloys. Mwang et al [3] reported a transformation sequence in TiNiFe alloy that was the parent B2→Incommensurate I→Rhombohedra R→Martensite M. But many authors [2,4] reported that the premartensitic structure of TiNi alloy is rhombohedra. It is known that the electric resistance increase ...


Modeling Of Laser Ultrasound Generation In A Weld Pool, John A. Johnson Jan 1988

Modeling Of Laser Ultrasound Generation In A Weld Pool, John A. Johnson

Review of Progress in Quantitative Nondestructive Evaluation

Finite element techniques are used to model laser generation of ultrasound and its propagation through a weld pool. The laser generation is modeled by assuming the reactive force to the laser ablation of the liquid is a stress perpendicular to the surface of the pool. The boundary of the pool is assumed to be spherical. The propagation of the sound waves from the laser source through the boundary into the solid metal is calculated assuming homogeneous properties in both the liquid and solid metal and temperature gradient effects are neglected. The results are compared to a series of experiments on ...


Laser Sound Generation In A Weld Pool, Nancy M. Carlson, John A. Johnson Jan 1988

Laser Sound Generation In A Weld Pool, Nancy M. Carlson, John A. Johnson

Review of Progress in Quantitative Nondestructive Evaluation

A welding machine requires three additional basic components for truly automated operation: sensors which detect physical properties of the weld; a model of the welding process which relates the controllable welding parameters, current, voltage, welding speed, etc., to the physical properties of the weld; and a control system which takes the signals from the sensors and converts them into a form which can be used for feedback control of the welding machine [1]. As part of a larger program to investigate all aspects of this problem, this study is concerned with the development of ultrasonic sensors to detect the physical ...


Formation Of Bcc Non-Equilibrium La, Gd And Dy Alloys And The Magnetic Structure Of Mg-Stabilized [Beta] Gd And [Beta] Dy , James W. Herchenroeder Jan 1988

Formation Of Bcc Non-Equilibrium La, Gd And Dy Alloys And The Magnetic Structure Of Mg-Stabilized [Beta] Gd And [Beta] Dy , James W. Herchenroeder

Retrospective Theses and Dissertations

The high temperature bcc allotrope of a rare earth metal has the potential for substantially different magnetic properties than the room temperature hexagonal (hcp or dhcp) counterpart because of its more symmetrical crystal field. The stabilization by alloying and quenching of this bcc phase was studied for La-M alloys where M is a non-rare earth metal from Group II or III. The factors influencing the stabilization, such as size of M and quench rate, are discussed. [gamma]La (bcc) could be retained over a composition range around the eutectoid composition by Mg or Cd alloying. A comparison of T[subscript ...