Embrittlement Analysis of $$\sum {{{{5}\left[ {{21}0} \right]} \mathord{\left/ {\vphantom {{{5}\left[ {{21}0} \right]} {\left( {\overline{1}\overline{2}0} \right)}}} \right. \kern-\nulldelimiterspace} {\left( {-{1}-{2}0} \right)}}}$$ FeAl Grain Boundary in Presence of Defects: An Ab Initio Study

Iron aluminide (FeAl) inter-metallic compounds are potential candidates for structural applications at high temperatures owing to their superior corrosion resistance, high temperature oxidation, low density and inexpensive material cost. However, the presence of defects can lead to reduction in the strength and ductility of FeAl-based materials. Here we present a density functional theory (DFT) study of the effect of the presence of defects including Fe and Al vacancies as well as H dopants at the substitutional and interstitial sites at a \(\sum {{{{5}\left[ {{21}0} \right]} \mathord{\left/ {\vphantom {{{5}\left[ {{21}0} \right]} {\left( {\overline{1}\overline{2}0} \right)}}} \right. \kern-\nulldelimiterspace} {\left( {\overline{1}\overline{2}0} \right)}}}\) FeAl grain boundary focusing on the energetics. The plane wave pseudopotential code Vienna Ab initio Simulation Package (VASP) in the generalized gradient approximation (GGA) is used to carry out the computations. The formation energy calculations showed that intrinsic defects such as Fe and Al vacancies probably form at the GB, indicated by their negative formation energies. These vacancies can further form defect complexes with H impurities, indicated by lowered formation energies, compact bonds and charge gain of H atoms. Electronic structure analysis showed stronger hybridization of 1s orbitals of H with Fe and Al atoms, which leads to the stabilization of these defects resulting in degradation of material strength.

     

Effect of Rolling Reduction on the P$$ \left\{ {011} \right\}\left\langle {455} \right\rangle $$ Recrystallization Texture in a Supersaturated Al-Mn-Mg Alloy

The hot band of a continuous cast (CC) Al-Mn-Mg alloy was cold rolled to different reductions ranging from 0 to 90 pct and then annealed at 482 °C for 3 hours. The effect of rolling reduction on the P recrystallization texture was investigated by X-ray diffraction. The results show that the recrystallization texture of the hot band is characterized by weak P orientation and 22.5 deg normal direction (ND) rotated cube orientation. The strength of the P texture increases with increasing rolling reduction. After 90 pct cold rolling, the recrystallization texture of the cold-rolled sheet is dominated by a strong P component.     

In Situ Study of Temperature Stability and Precipitation Kinetics of $$\delta $$ and $$\eta $$ Phases in Nickel Base Superalloys

Metallurgical and Materials Transactions A - The present study aims at determining the temperature stability and precipitation kinetics of phases like $$\delta $$ -Ni $$_3$$ Nb, $$\delta $$ -Ni...     

Microstructure-Based Estimation of Strength and Ductility Distributions for $$\alpha +\beta $$ Titanium Alloys

Titanium alloys are processed to develop a wide range of microstructure configurations and therefore material properties. While these properties are typically measured experimentally, a framework for property prediction could greatly enhance alloy design and manufacturing. Here a microstructure-sensitive framework is presented for the prediction of strength and ductility as well as estimates of the bounds in variability for these properties. The framework explicitly considers distributions of microstructure via new approaches for instantiation of structure in synthetic samples. The parametric evaluation strategy, including the finite element simulation package FEpX, is used to create and test virtual polycrystalline samples to evaluate the variability bounds of mechanical properties in Ti-6Al-4V. Critical parameters for the property evaluation framework are provided by measurements of single crystal properties and advanced characterization of microstructure and slip system strengths in 2D and 3D. Property distributions for yield strength and ductility are presented, along with the validation and verification steps undertaken. Comparisons between strain localization and slip activity in virtual samples and in experimental grain-scale strain measurements are also discussed.

     

Thickness-Dependent Permanent Magnet Properties of Zr $$_{2}$$ Co $$_{11}$$ Thin Films Grown on Si with Pt Underlayer

Metallurgical and Materials Transactions A - Zr-Co is one of the essential magnetic materials due to its interesting magnetic and structural properties. In this work, we studied the magnetic and...     

First Order Pyramidal Slip of 1/3\ \langle 1\bar{2}10\rangle Screw Dislocations in Zirconium

Atomistic simulations, based either on an empirical interatomic potential or on ab initio calculations, are used to study the pyramidal glide of a \(1/3\ \langle 1\bar{2}10\rangle \) screw dislocation in hexagonal close-packed zirconium. Generalized stacking fault calculations reveal a metastable stacking fault in the first order pyramidal \(\lbrace 10\bar{1}1 \rbrace \) plane, which corresponds to an elementary pyramidal twin. This fault is at the origin of a metastable configuration of the screw dislocation in zirconium, which spontaneously appears when the dislocation glides in the pyramidal plane.     

Differential effect of right and left vagal stimulation on right and left circumflex coronary arteries

In anasthetised, closed-chest dogs in complete heart block that were paced at a ventricular rate of 100 beats/min, vagal stimulation increased right coronary (RC) flow by 46% and conductance by 59%, but these increases were less than those measured in the left circumflex coronary (LCC) flow (66%) and conductance (80%). Both the right and left vagus nerves affected RC and LCC flow, the left vagus having the greater effect. The response to vagal stimulation is not limited at higher ventricular rates.     

Cyclic Deformation Behaviors of $$ [\bar{5}79] $$-Oriented Al Single Crystals

During the cyclic deformation of [[`5]79] [\bar{5}79] , Al single crystals with a high stacking fault energy produced slip bands that were characterized by wavy slip. Its cyclic stress response curve demonstrated that the specimen experienced hardening–softening–secondary hardening in sequence with repeated fluctuation stresses usually less than 10 MPa, which is far lower than those of Cu, Ni, and Ag single crystals. Finally, the whole surface of the Al single crystals was covered with intense intrusion and extrusion, and the cell structure is the most typical dislocation arrangement. These cells mainly comprise loose clusters of dislocations, which move more freely. In the center of the cell, the dislocation density is relatively low, and most dislocations concentrate in the cell wall. At room temperature, compared with cyclically deformed Cu, Ni, and Ag single crystals, the cyclic deformation behaviors of Al single crystals show significant differences, which are highlighted in this study.     

Remembering left–right orientation of pictures.

Studied orientation retrieval and recognition memory for pictures in 32 undergraduate or graduate students. Results indicate an asymmetry in classifying test items as "same" vs "different" in left–right orientation. Identical copies of previously viewed items were classified more accurately than left–right reversals of those items. Response bias could not explain this asymmetry, and, moreover, correct "same" and "different" classifications were independently manipulable. Whereas repetition of input pictures (1 vs 2 presentations) affected primarily correct "same" classifications, retention interval (3 hrs vs 1 wk) affected primarily correct "different" classifications. Repetition but not retention interval affected judgments that previously seen pictures (both identical and reversed) were "old." Findings support a dual-process hypothesis that links "same" classifications to high familiarity, and "different" classifications to conscious sampling of images of previously viewed pictures. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences between right and left lateral chest radiographs

Differences between 150 normal right lateral chest teleroentgenographs and 150 left laterals (infants, children, and adults) were evaluated and determined to be greater than has been generally appreciated. On the left lateral view the left leaf is distinguished from the right leaf by the following generalizations: anteriorly the left leaf is lower; posteriorly it is higher as is its costrophrenic sulcus; it intersects the relatively flattened right leaf near the posterior heart border; the stomach bubble and/or colon are immediately subjacent; there is no segmental obliteration by the inferior vena cava as there often is with the right leaf; in adults the outline of the left leaf is often sharper. When both major fissures can be identified, the left almost always intersects its diaphragmatic leaf posterior to and more vertically than the right fissure.     

Spatial localization in left and right visual fields.

Presented a series of single dots tachistoscopically in either the left or the right visual field, Ss task being to locate the dot on a spatial map depicting all of the lot locations presented. 7 experiments were carried out with 232 right-handed male and female undergraduates. For men, localization of the dot was more accurate in the left than in the right visual field, under all testing conditions. Women showed the left-field superiority under some testing conditions; under others they showed no difference between fields. There was no sex difference in over-all accuracy of performance, and simple detection of a dot was not more accurate in 1 field than another for either sex. Results are discussed in terms of a probable "spatial coordinate" system in the right hemisphere of the brain. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Echocardiographic findings in left ventricular to right atrial shunts

The echocardiographic abnormalities of tricuspid valve motion in 2 patients with left ventricular to right atrial shunts are described. In both patients the abnormal anatomy was defined at surgery, in one patient the shunt being above the tricuspid valve leaflets (supravalvar) and in the other patient through the septal leaflet (intravalvar). Different patterns of tricuspid valve systolic fluttering were seen in these two cases and the possible reasons for this are discussed. After surgical closure of the defects the systolic fluttering of the tricuspid valve was no longer observed. Echocardiography appears to be useful in detecting the presence of left ventricular to right atrial shunts which otherwise may be difficult to diagnose.     

Memory biases in left versus right implied motion.

People remember moving objects as having moved farther along in their path of motion than is actually the case; this is known as representational momentum (RM). Some authors have argued that RM is an internalization of environmental properties such as physical momentum and gravity. Five experiments demonstrated that a similar memory bias could not have been learned from the environment. For right-handed Ss, objects apparently moving to the right engendered a larger memory bias in the direction of motion than did those moving to the left. This effect, clearly not derived from real-world lateral asymmetries, was relatively insensitive to changes in apparent velocity and the type of object used, and it may be confined to objects in the left half of visual space. The left–right effect may be an intrinsic property of the visual operating system, which may in turn have affected certain cultural conventions of left and right in art and other domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction

BACKGROUND: There is still no agreement about the optimal method of surgical relief of fixed subaortic stenosis, particularly the severe forms. OBJECTIVES: The purpose of this study was to describe a new technique for the relief of subaortic stenosis based on analysis of the functional anatomy of the left ventricular outflow tract and pathophysiologic features of subaortic stenosis. Methods and patients: We propose that one of the basic abnormalities in subaortic stenosis is interference with the hinge mechanism provided by the 2 fibrous trigones with progressive deposition of fibrous tissue in these angles. The technique described in this paper consists of excision of all components of the fibrous "ring," with mobilization of the left and right fibrous trigones. This results in the restoration of the normal dynamic behavior of the left ventricular outflow tract with maximal widening of the outflow tract as the result of backward displacement of the subaortic curtain and anterior leaflet of the mitral valve. This technique has been used in 57 consecutive patients who ranged in age between 5 months and 56 years (mean, 15.5 +/- 10.6 years). Gradients across the left ventricular outflow tract were between 45 and 200 mm Hg (mean, 86.7 mm Hg). Additional lesions were present in 10 patients, and 7 patients had had 8 previous operations on the left ventricular outflow tract. At operation, in addition to resection of subaortic stenosis, 3 patients had aortic valvotomy, 2 patients had homograft replacement of the aortic valve, 7 patients had patch closure of a ventricular septal defect, and 1 patient had open mitral valvotomy. RESULTS: There were 2 early deaths and 1 late sudden death during the follow-up period that ranged from 1 month to 25 years (mean, 15. 2 years). One patient experienced the development of endocarditis on the aortic valve 7 years after operation, which was successfully treated by homograft replacement. Postoperative gradients across the left ventricular outflow tract varied from no gradient to 30 mm Hg (mean, 8 mm Hg). There were no instances of recurrence of a gradient across the left ventricular outflow tract. CONCLUSION: It is concluded that mobilization of the left and right fibrous trigones results in durable relief of subaortic stenosis.