SUMMER INSTITUTE ON LABOUR ECONOMICS AND INDUSTRIAL RELATIONS ...

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• cours - matière potentielle : last 25 years
• exposé
• exposé - matière potentielle : adam
• cours - matière potentielle : last 50 years
• exposé - matière potentielle : adam

1SUMMER INSTITUTE ON LABOUR ECONOMICS AND INDUSTRIAL RELATIONS, DEPARTMENT OF LABOUR & SOCIAL WELFARE, PATNA UNIVERSITY, PATNA-5 THE STRUCTURE OF WAGES BY Dr. G.P. Sinha, Ph.D. (Cornell), University Professor and Head, Department of Labour & Social Welfare, Patna University, Patna Introduction There are two sources of income in society : property and labour. Labour here is used in its widest connotation ranging from the labour of the unskilled to the labour of engineers or other most highly skilled and talented groups of people.

• objective terms
• terms of a fixed percentage
• early days of the evolution of the job evaluation methods
• economic forces
• relative position
• wage structure
• labour
• wages
• theories
• 2 india
• india

Sujets

• Exposé
• Wotton
• University of Patna
• Wootton
• In?ija
• Royaume-Uni

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• Publié par: odwo
• Nombre de lectures: 37
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

ASM Handbook, Volume 9: Metallography and Microstructures Copyright © 2004 ASM International®
G.F. Vander Voort, editor, p493–512 All rights reserved.
DOI: 10.1361/asmhba0003752 www.asminternational.org
Color Metallography
George F. Vander Voort, Buehler Ltd.
THE USE OF COLOR in metallography has opment of wavelength-dispersive spectrometers etchants that produced color either by immer-
a long history, with color micrographs published and energy-dispersive spectrometers used on sion, sometimes in boiling solutions, or electro-
lytically. Historical information on these etch-over the past eighty-some years. A number of electron microprobe analyzers and scanning
general articles (Ref 1–15) have been published microscopes, the color of inclusions us- ants can be found in Ref 16.
reviewing methods and applications. ing different illumination modes was part of the Tint etchants may color either the anodic (ma-
Natural color is of use in only a few classic identification schemes used. However, natural trix) or cathodic constituents. There are also
metallographic applications. Prior to the devel- color has limited applicability. electrolytic reagents known as anodizing solu-
Color can be created by optical methods, such tions. They have been used most commonly with
as with polarized light and differential interfer- aluminum and its alloys. These solutions may
ence contrast illumination. Polarized light ex- produce a thin film on the surface, with a degree
amination is extremely useful for studying the of roughness. Examination in bright field reveals
structure of certain metals, without etching, that little, but polarized light reveals the structure
have noncubic crystal structures, such as beryl- clearly.
lium, hafnium, -titanium, uranium, and zirco- There are other procedures to create interfer-
nium. In many cases, polarized light can be used ence films using heat (heat tinting), vapor de-
with etched specimens, regardless of their crystal position, or by reactive sputtering. Color can be
structure, to produce color. Differential interfer- observed with bright-field illumination but often
ence contrast reveals height differences between can be enhanced using polarized light.
constituents and the matrix, but in most cases,
the color is of esthetic value only.
Optical Methods forColor etching methods are widely used, al-
though they are not universal. Color etchants Producing Color
have been developed for a limited number of
metals and alloys, and they are not always easy There are few instances where naturally oc-
to use, nor are they fully reliable. Color etchants curring color differences are observed in metallic
Microstructure of a porous high-carbon steel are used by immersion or electrolytically. AFig. 1 systems. Specimens plated with copper or gold
powder metallurgy specimen infiltrated with complete listing of all color etchants is beyond are a common example. There are two main op-
copper showing the natural color of the copper, which is the scope of this article, but good compilations tical methods for producing coloring: polarizedeasier to see when the steel has been tint etched (revealing
are available (Ref 7, 10–15). Aside from the im-coarse plate martensite and retained austenite)
mersion tint etchants, there are a number of older
Microstructure of as-cast Au-22%Al showing Cuprous oxide in tough pitch arsenical copper Microstructure of walnut (plane perpendicular toFig. 2 Fig. 3 Fig. 4
the “purple plague,” AuAl intermetallic (red- (hot extruded and cold drawn) viewed in dark the trunk axis) showing the cells and pores re-2
dish), surrounded by the Al-AuAl eutectic after polishing field, revealing the classic ruby-red color. Magnification vealed using dark-field illumination. Magnification bar is2
to a 1 lm finish. Magnification bar is 50 lm long. bar is 10 lm long. 100 lm long.494 / Metallographic Techniques
light and differential interference contrast. In the natural color of copper is clearly seen against nium, uranium, zinc, and zirconium. Figure 5
both cases, color per se is of minimal value be- the steel matrix. It may be easier to see the cop- shows the grain structure near the surface of an
yond simple esthetics. The color of inclusion electron-beam-melted crystal bar of high-purityper color when the steel matrix is etched. Figure
phases in bright field, dark field, and polarized zirconium (not etched) that was hot rolled, an-1 shows an example of porous high-carbon steel
light has been used for identification purposes nealed, and cold drawn. The deformation processthat was partially infiltrated with liquid copper,
for many years. produces mechanical twins that are quite numer-where the natural color of the copper can be eas-
Natural color is not a common occurrence in ous at the surface but nearly absent in the inte-ily observed. There is a substantial difference in
metallic systems; many metals have a similar rior. Other examples of color developed with po-the reflectivity of iron and copper. Etching of the
white color. When polished, only a few metals larized light on as-polished specimens of metalshigh-carbon martensitic/pearlitic matrix in-
exhibit a color other than white; for example, with noncubic crystal structures are shown increases the image contrast difference, making it
gold and copper appear yellow when polished. Fig. 6, hafnium; Fig. 7, ruthenium; and Fig. 8,easier to see the copper color. The so-called
Platings of these metals can be easily recognized Cd-20% Bi.“purple plague,” the intermetallic phase Al Au2
by their color. A classic example of natural color Unfortunately, not all noncubic phases orthat can occur in brazing of integrated circuits,
differences is the detection of liquid metal em- metals respond well to polarized light. In somehas a natural purple or red-violet color, as illus-
brittlement in steels due to copper. In this case, cases, a well-prepared specimen responds to po-trated in Fig. 2. Nitrides and some inclusions ex-
larized light, revealing the microstructure quitehibit specific colors when examined with bright-
clearly but without appreciable color. The con-field illumination, but overall, natural color is
trast produced, and the color intensity, may beuncommon with metals and alloys.
a function of both the degree of anisotropy ofDark-Field Illumination. Inclusions in met-
the metal or alloy and the quality of specimen
als have been identified using known colors
when viewed with bright field, dark field, or po-
larized light (Ref 17). Cuprous oxide, Cu O, in2
tough pitch copper, for example, is easily rec-
ognized because it glows ruby red in dark-field
illumination (Fig. 3) but appears bluish-gray in
bright field. Cuprous sulfide, Cu S, has a similar2
color in bright field but remains dark and dull in
dark field (Ref 18). Wood also exhibits natural
color in dark field, as shown in Fig. 4.
Polarized Light. There are purely optical
methods for generating color images employing
polarized light and differential interference con-
trast illumination. Polarized light examination is
useful with phases or anisotropic metals that
Extensive mechanical twinning was observed inFig. 5 have noncubic crystallographic structures (Ref
high-purity, electron-beam-melted zirconium af-
2), such as antimony, beryllium, cadmium, co-ter hot working and cold drawing. Viewed in polarized
light. Magnification bar is 100 lm long. balt, magnesium, scandium, tellurium, tin, tita-
Microstructure of as-cast pure ruthenium, as-pol-Fig. 7
ished and viewed in polarized light plus sensitive
tint, revealing a mixture of equiaxed and columnar hex-
agonal close-packed grains and some small shrinkage cav-
ities (black). The magnification bar is 200 lm long.
Microstructure of Cd-20%Bi in the as-cast con-Fig. 8
dition, unetched and viewed with polarized light
(slightly off the crossed position) plus sensitive tint, reveal-
ing cadmium dendrites of various orientation. The inter-
Microstructure of wrought pure hafnium, with an as-polished specimen viewed in polarized light plus sensitive dendritic constituent is a eutectic of cadmium and bismuthFig. 6
tint, revealing an equiaxed alpha hexagonal close-packed grain structure. A few mechanical twins can be seen but is too fine to resolve at this magnification. Magnifica-
at the surface (arrows). The magnification bar is 100 lm long. tion bar is 200 lm long.Color Metallography / 495
preparation. The quality of the surface appears etchants for magnesium did not provide this im- with a specific reagent that produces etch pits or
to be the key factor, but the quality of the op- provement). furrows within the grains that respond to polar-
tical system is also very important. In some In some cases, isotropic metals and alloys may ized light. Figure 11 shows an example of an alu-
cases, the color response in polarized light can respond to polarized light after being etched with minum brass (Cu-22%Zn-2%Al) that was cold
be markedly improved after etching specimens a particular reagent that either produces an aniso- worked and annealed at 750 C (1380 F). The
having noncubic crystal structures with some tropic film on the surface or roughens the surface. specimen was etched with the classic potassium
specific reagent. Figure 9 shows the grain struc- In some cases, anodizing solutions may produce dichromate reagent, which produces a black-and-
ture of hot-rolled hexagonal close-packed (hcp) an optically anisotropic film on the surface that white grain co