scholarly journals I. The behaviour of single crystals of aluminium under static and repeated stresses

1927 ◽  
Vol 226 (636-646) ◽  
pp. 1-30 ◽  
Keyword(s):  
Single Crystals ◽  
National Physical Laboratory ◽  
Micro Structure ◽  
Important Conclusion ◽  
X Ray ◽  
Slip Bands ◽  
Physical Laboratory ◽  
Slip Planes ◽  
Experimental Facilities ◽  
Crystalline Aggregates

In a previous paper were recorded the results of an investigation into the effects of repetitions of stress on the micro-structure of various metals in the form of crystalline aggregates, the main purpose of the investigation being a study of the causes of fracture under repeated stresses of relatively low magnitude. One important conclusion derived from the experiments was that the action of slipping was not, as had been previously stated, a weakening process in itself. Up to a point the effect of slip was actually to increase the resistance of the metal to further slip. Eventually, however, this strengthening action was exhausted, and failure commenced by the formation of a crack. It was suggested that failure occurred when the amount of strain-hardening by slip exceeded a certain limiting amount. No definite evidence could be obtained on this point, but it was considered that further information might be obtained if attention was directed to a material more simple in structure than a crystalline aggregate. In particular, it was desired to eliminate the effects of the crystal boundaries, whose nature is at present unknown. This could be accomplished if specimens cut entirely from one crystal were employed. Further, it should be possible to verify the assumption, commonly made, that slip bands represent the traces of actual “slip planes” on the surface of the specimen, and to relate these with the atomic structure of the material. Through the kindness of Prof. Carpenter and Miss Elam a number of large single crystals of aluminium were prepared and presented and have been used throughout this work. At that time the necessary experimental facilities for X-ray work were not available to the authors at the National Physical Laboratory. Prof. Carpenter offered to arrange for the X-ray analyses to be undertaken by his assistant, Miss C. F. Elam, at the Royal School of Mines. This offer was gratefully accepted and the authors are greatly indebted to Miss Elam for carrying out this section of the work.

scholarly journals The behaviour of a single crystal of zinc subjected to alternating torsional stresses

1929 ◽  
Vol 123 (791) ◽  
pp. 143-167 ◽  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
National Physical Laboratory ◽  
Stress System ◽  
Lattice Systems ◽  
Hexagonal Close Packed ◽  
Physical Laboratory ◽  
General Investigation ◽  
Slip Planes ◽  
Promising Line

The present experiment has been carried out in the course of a general investigation into the causes and characteristics of the failure of metals under repeated cycles of stress which has been in progress for some years past at the National Physical Laboratory. As this research proceeded, one definite and promising line of investigation suggested itself in the study of the behaviour of single metallic crystals under repeated stress systems, and, as a commencement, attention is being directed to typical metals crystallising in the cubic (face-centred, also body-centred), close packed hexagonal, and rhombohedral space lattice systems. The investigation, when completed, should not only give certain fundamental data concerning fatigue phenomena, but also, when studied in conjunction with the classical researches of Mark, Polanyi and Schmid, Taylor, Elam, and Farren—who have studied in detail, the characteristics of deformation of single crystals under static stressing—afford some contribution towards the discovery of the general laws of deformation of metals subjected to any stress system. Previous reports have described experiments on single crystals of aluminium (face-centred cubic) and iron (body-centred cubic). The present paper describes an experiment on a single crystal of zinc, a metal crystallising in the hexagonal (close-packed) lattice. The deformation of zinc crystals under statical direct stress has received much attention from Mark, Polanyi and Schmid. They showed clearly that the principal slip plane is the basal (0001) plane, the direction of slip being that of the most highly stressed (shear stress) primitive direction (normal to the 1̄21̄0, 1̄1̄20, or 21̄1̄0 plane) contained by the basal plane. In the last stages of deformation, however, they found that deformation was consistent with slip occurring on planes apparently perpendicular to the basal planes, and they suggested that prismatic planes were also slip planes; they were unable, however, to establish this identity.

scholarly journals The application of X-rays to the study of alloys

1925 ◽  
Vol 108 (748) ◽  
pp. 643-654 ◽  
Keyword(s):  
Single Crystals ◽  
National Physical Laboratory ◽  
Photographic Method ◽  
X Rays ◽  
X Ray ◽  
Powder Method ◽  
Physical Laboratory ◽  
Small Crystals ◽  
Ray Methods ◽  
Great Advance

Since the middle of last century it has been known that the alloys, obtained by melting together two or more metals, are conglomerates of small crystals. As it is impossible to study them under the polarizing microscope because of their high absorbing power for light, and as they are seldom obtained in crystals with faces sufficiently well developed to allow a measurement of their angles, our crystallographic knowledge has been, until recently, extremely small. When, therefore, the X-ray methods came to the assistance of the metallurgist they were sure of a welcome. In 1922, Bain, using the powder-photograph method of Debye and Hull, carried out some very important pioneering work. In 1924, Owen and Preston, of the National Physical Laboratory, working in conjunction with Rosenhain studied the Cu-Al and Cu-Zn systems. They used a powder method with an ionization spectrometer. Their work marked a great advance, on account of the precision of their measurements and their detailed description of the preparation of the samples of alloys. At the same time Westgren and Phragmen, working in Stockholm with a photographic method, studied independently the same systems as Owen and Preston, and obtained results of equal precision. They extended the work in certain directions by making a more thorough investigation of single crystals. They have now undertaken an extensive research on several alloys and on steels.

scholarly journals The thermal and electrical conductivity of a single crystal of aluminium

1927 ◽  
Vol 115 (770) ◽  
pp. 236-241 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Single Crystals ◽  
Test Specimen ◽  
Average Diameter ◽  
National Physical Laboratory ◽  
Present Communication ◽  
Uniform Size ◽  
The Third ◽  
Physical Laboratory

The recent work of Carpenter and Elam on the growth of single crystals of large dimensions has rendered possible the study of the physical constants of single crystals of the commoner metals, and the present communication describes the determination of the thermal and electrical conductivity of aluminium in the form of an isolated crystal. The form of the crystal investigated is shown in fig. 1. This crystal had been prepared at the National Physical Laboratory employing the technique described by Carpenter in “Nature,” p. 266, August 21, 1926, which briefly is as follows:— The test specimen is machined and subjected to three treatments, thermal, mechanical, and thermal. The first treatment is necessary to soften the metal completely and produce new equiaxed crystals of so far as possible uniform size, the average diameter being 1/150 inch. The second consists in straining these crystals to the required amount, and the third in heating the strained crystals to the requisite temperature, so that the potentiality of growth conferred by strain could be brought fully into operation.

Address of the President, Professor P. M. S. Blackett, C.H., at the Anniversary Meeting, 30 November 1966

1967 ◽  
Vol 167 (1006) ◽  
Keyword(s):  
National Physical Laboratory ◽  
Simple Approach ◽  
Ionic Crystals ◽  
X Ray Diffraction ◽  
Complete Structure ◽  
Principal Role ◽  
X Ray ◽  
Physical Laboratory ◽  
Royal Institution

The Copley Medal is awarded to Sir Lawrence Bragg, O.B.E., M.C., F.R.S. Bragg’s career has precisely coincided with the growth of a major field of science—the X-ray diffraction analysis of crystal structures. This had its beginning in his own early researches, and he has throughout played a principal role by his leadership at a series of laboratories, at Manchester, at the National Physical Laboratory, at Cambridge and at the Royal Institution, and in many other ways. He was the first to determine the atomic arrangement in a crystal (sodium chloride), and this work marked the introduction of a technique which has since been successfully applied to increasingly complicated molecules, culminating in the complete structure determination of the protein lysozyme at the Royal Institution a year before his retirement. Bragg has been prominent in the development of methods, beginning with the Law named after him; he also pioneered or encouraged the application of these methods in several fields—ionic crystals, elementary oxides, silicates, metals and proteins. The striking characteristic of Bragg as a scientist has been his direct and simple approach to complicated physical situations; his solutions of problems have a lucidity and simplicity which, in retrospect, make one forget how baffling they often seemed in advance.

Alloys Research Committee: The Work of the Alloys of Iron Research Committee

1934 ◽  
Vol 127 (1) ◽  
pp. 277-298 ◽  
Author(s):  
C. H. Desch
Keyword(s):  
National Physical Laboratory ◽  
Basic Material ◽  
High Melting Point ◽  
Research Committee ◽  
Laboratory Methods ◽  
Physical Methods ◽  
X Ray ◽  
Upper Limit ◽  
Physical Laboratory ◽  
Systematic Knowledge

The Alloys Research Committee of The Institution of Mechanical Engineers began its work in 1890, and from 1902 onwards the investigations were conducted in the National Physical Laboratory. The Eleventh Report, published in 1921, dealt very fully with the light alloys of aluminium. At that stage it was decided that further research should be devoted to the alloys of iron with the object of determining the fundamental nature of the alloys of iron with various metals and non-metals to serve as a basis for a more systematic knowledge of the steels used in practice. The investigation has comprised the construction of equilibrium diagrams using thermal, microscopical, X-ray, and other physical methods. Iron being more sensitive to the influence of minute quantities of impurities than most other metals, it was necessary to prepare very pure iron as the basic material. Since 1921, the alloys of iron with oxygen, phosphorus, silicon, chromium, and manganese have been studied. As all the alloys are of high melting point, many new laboratory methods have had to be developed, the technique of experiments at high temperatures becoming more difficult the higher the upper limit is raised. In the course of the research, therefore, it has been necessary to prepare new refractories and to design special forms of apparatus in order to avoid contamination. The paper contains a summary of the results obtained in the course of the work, and it is shown how these bear upon the improvement of steels for structural and engineering purposes. The investigation is being extended to other elements, and ultimately to the influence of more than one solid element when present simultaneously in the alloy.

Address of the President, Professor P. M. S. Blackett, C.H., at the Anniversary Meeting, 30 November 1966

1967 ◽  
Vol 296 (1444) ◽  
Keyword(s):  
National Physical Laboratory ◽  
Simple Approach ◽  
Ionic Crystals ◽  
X Ray Diffraction ◽  
Complete Structure ◽  
Principal Role ◽  
X Ray ◽  
Physical Laboratory ◽  
Royal Institution

The Copley Medal is awarded to Sir Lawrence Bragg, O. B. E., M. C., F. R. S. Bragg’s career has precisely coincided with the growth of a major field of science─the X-ray diffraction analysis of crystal structures. This had its beginning in his own early researches, and he has throughout played a principal role by his leadership at a series of laboratories, at Manchester, at the National Physical Laboratory, at Cambridge and at the Royal Institution, and in many other ways. He was the first to determine the atomic arrangement in a crystal (sodium chloride), and this work marked the introduction of a technique which has since been successfully applied to increasingly complicated molecules, culminating in the complete structure determination of the protein lysozyme at the Royal Institution a year before his retirement. Bragg has been prominent in the development of methods, beginning with the Law named after him; he also pioneered or encouraged the application of these methods in several fields—ionic crystals, elementary oxides, silicates, metals and proteins. The striking characteristic of Bragg as a scientist has been his direct and simple approach to complicated physical situations; his solutions of problems have a lucidity and simplicity which, in retrospect, make one forget how baffling they often seemed in advance.

X-ray diffraction imaging of dislocation generation related to microcracks in Si wafers

2010 ◽  
Vol 25 (2) ◽  
pp. 99-103 ◽  
Author(s):  
J. Wittge ◽  
A. Danilewsky ◽  
D. Allen ◽  
P. McNally ◽  
Z. J. Li ◽  
...  
Keyword(s):  
Large Scale ◽  
Rear Surface ◽  
Indentation Load ◽  
X Ray Diffraction ◽  
Dislocation Generation ◽  
X Ray ◽  
Slip Bands ◽  
Slip Planes ◽  
Edge Defects ◽  
Diffraction Imaging

The nucleation of dislocations at indents in silicon following rapid thermal annealing (RTA) has been examined by X-ray diffraction imaging (topography). For indentation loads below 200 mN, no slip bands were generated from the indent sites following RTA at 1000 °C under spike conditions. Upon plateau annealing at 1000 °C, slip dislocations were propagated from some indents but not all. Slip was also observed from edge defects not associated with indentation. For 500-mN indentation load, large scale dislocation sources were generated from the indent sites propagating on two of the four {111} slip planes. These dislocations multiplied into macroscopic-scale slip bands. A significant change in morphology was observed in the 60° dislocation segments after the screw segment reached the rear surface of the wafer. Dislocations changed line direction and in some cases appeared to leave the Peierls trough during glide.

scholarly journals The thermal and electrical resistance of bismuth single crystals. The effects of temperature and magnetic fields

1939 ◽  
Vol 170 (943) ◽  
pp. 561-583 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Magnetic Fields ◽  
Single Crystals ◽  
Preliminary Investigation ◽  
National Physical Laboratory ◽  
Transverse Magnetic ◽  
Published Data ◽  
Physical Laboratory ◽  
Electrical Conductivities

The anomalous physical properties of bismuth, particularly as regards the reduction of the thermal and electrical conductivities in magnetic fields, have claimed the attention of a number of workers in the past. Most of the published data refers to the electrical conductivity, owing, no doubt, to the greater ease of measurement; and but little reliable work appears to have been done on the thermal conductivity, at any rate in the case of single crystals. Lounds (1902) carried out thermal-conductivity measurements employing magnetic fields up to about 5000 gauss, but the accuracy of his results was prescribed by the limitations of the method and the smallness of his crystals. Kapitza (1928) undertook an extensive investigation on the electrical conductivity of single crystals using very intense momentary fields. Banta (1932) published thermal-conductivity values using fields up to 8000 gauss, while more recently de Haas and Capel (1934) have made thermal measurements, in the absence of a field, at liquid-air and liquid-hydrogen temperatures. The results of a preliminary investigation (Kaye and Higgins 1929 a ) at the National Physical Laboratory on the change in thermal conductivity of bismuth single crystals in transverse magnetic fields were published in 1929. In this work, specimens, which were cut in the form of disks 25 mm. in diameter and 2 mm. thick from a large crystal grown by Bridgman’s method (1925), were tested in a “plate” type of apparatus, field strengths up to 11,000 gauss being employed in a 38 mm. air gap.

Sign in / Sign up

Export Citation Format

Share Document