Manual 9810176

Manual 9810176
on Fundamentals
of General Metallography
Ing. Gerhard Umlauff,
Hennigsdorf Institute of Technology
The micrographs included in this series of projection films
on fundamentals of general metallography were made available
by Laboratory of Metallography, Materials ungineering Department,
Hennigsdorf Institute of Technology.
Designed by
Günter Brabant
Prepared for publication by
Dipl.-Ing. paed. Marianne Quendt,
Dipl.-Ing. paed. Ginter Zweynert
Published by
Zentralstelle für Bildungswesen des Schwermaschinen-
und Anlagenbaus
*B-7010 Leipzig, Barfussgisschen 12
on behalf of
Institut fur berufliche Entwicklung
BIR-1080 Berlin, Franzósische Strasse 47
111-6-15 882-81 Ag 689-37-81
Copyright © 1980 by ZSB Leipzig
This series of projection films on fundamentals of gen-
eral metallography can be used for the theoretical edu-
cation and practical training in metal fabrication. It
can also be used for further and refresher training in
the metal-fabricating field. It covers the following sub-
jects: Film no.
(1) Crystalline structure
of metals 1, г, 5
(2) Structure and real lattice 3, 4, 5, 6
(3) Methods of examination 7 thru 13
(4) Zutectic diagram 14
(5) Solid solution diagram 8, 9, 15
(6) Precipitations from
solid solutions 16
(7, Deformation of metals 17, 18, 19
(8) Recrystallization 19, 20
(9) Iron-carbon diagram 21 thru 26
To aid instructors in making preparations for lessons and
avoid misinterpretations of the contents of projection
films, all of the films have detailed explanations attach-
ed to them. Ease of comprehensibility called for the lib-
eral use of colors in the design of projection films on
methodological principles.
All crystallographic relationships (e.g., lattices and
unit cells) were marked in blue, whereas transitions to
higher temperatures accompanied by state changes were
marked in red.
Cooling curves of thermal analysis and heating curves of
thermal treatment were plotted against a blue background,
whereas constitutional diagrams and those relating to
strength properties were plotted against yellow and green
backgrounds, respectively.
Nicrographs of metals were unilaterally fixed to base
films, thus providing for various forms of representation
during classes. To enable instructors to plot their own
diagrams, blank films nos. 27 and 28 were provided with
centimeter grids. A4 size films are used together with
frames to take up base films.
u Ba
The films in this series are contained in suitable bags
which together with the booklet and frame are accommodated
in a plastic folder, thus providing for ease of storage
together with other types of information carriers.
List of projection films
Film no.
N ND № ГО AN № ND MN fo od —% —® a 4 A A SS
© SINN SW N —® © О O Y arar EW ГО =
Film title
Crystal lattice
Grain and grain boundary
Unit cells
Crystal growth
Real lattice structure
Etching possibilities
Macro- and micro-etching
Coarse and fine grains
Segregations in rimmed steel
Metallurgical microscope
Thermal analysis
Curve of solidification
Solid solutions
Precipitations from solid solutions
Stress-strain diagram
Process of deformation
Work hardening of copper
Recrystallization of copper
Iron-carbon diagram no. 1
lron-carbon diagram no. 2
Steel corner of the iron-carbon diagram
Primary and secondary cementite
Blank film with centimeter grid
Blank film with centimeter grid
Sxplanations of films
Film no. 1
Crystal lattice
It is essential to point out that the crystalline struc-
ture of metals can be explained only with the use of a
model theory. To convey such model concepts, film no. 1
should be presented together with films nos. 2 and 3 which
are concerned with grains and grain boundaries and with
unit cells, respectively. By representing rows, lattice
planes, space lattices, and unit cells and indicating the
order of magnitude of the lattice constant, it is possible
to explain the abstraction from the solid sphere model to
the point lattice. Geometric laws can thus be understood
more easily.
If required, portions of the
film presented can be cover-
ed during instruction (e.g.,
representation of the lattice
plane and unit cell). This
allows the students' atten-
tion to be concentrated on
what is being discussed.
rilm no. 2
Grain and grain boundary
This film compares a model concept that is used to explain
the polycrystalline structure of metals with real struc-
tural conditions, “hen viewing this film it is necessary
to take into account the different scales. This film can
be used to explain the term anisotropy which indicates
variation in properties in different directions, e.g., in
a steel sheet. (hen discussing the contents of the film,
halves thereof can be covered and compared with micrographs,
and more particularly film no. 7 (etching possibilities),
film no. 8 (macro- and micro-etching), and film по. 9
(coarse and fine grains).
Film no. 3
Unit cells
This film shows a body-centered cubic unit cell and a
face-centered cubic unit cell as the most important rep-
resentatives of the crystal systems. It should be noted
that multifarious cubic unit cells occur in nature and
that not only the form and size but also the configuration
or arrangement of the atoms are of importance (properties
of metals).
It is appropriate for a table of lattice constants and
other values to be set up during discussion of the subject
The imaginative faculty of students can be substantially
supported through using a combination of sphere model and
film representation.
Film no. 4
Crystal growth
This film shows, in a series of single images, the process
of crystallization during transition from the liquid to
the solid phase (anisotropy of crystal growth). It should
be pointed out that crystals will not assume a stable posi-
tion in the melt but will move within the melt up to a
certain degree of solidification. Since impurities often
tend to accumulate in the residual melt during solidifica-~
tion, segregations in the structure will occur. It is in
this particular context that film no. 10 (segregations in
rimmed steel) can be referred to. The objective should be
to reduce model concepts to reality. Such terms as real
structure and structural faults can be introduced to ex-
plain the actual behavior of materials. This confirms the
possibility of affecting the properties of materials.
Also, film no. 4 can be used to discuss the dependence of
the grain boundary upon the number of nuclei present. The
individual images of this film can be presented one after
the other, with those that are not be shown being covered.
Film no. 5
Real lattice structure
This film, which is a continuation of film no. 4 (crystal
growth), is concerned with the structural faults of crys-
tal lattices. The extent to which these forms of real
lattice are discussed in classes is left to the discretion
of the instructor. However, it is essential that he should
discuss at least vacant lattice sites, exchange atoms,
and interstitial impurities. It should be pointed out
that the exchangeability of atoms (the atomic volume must
be no greater than fifteen percent of the atoms of the
basic lattice) and incorporability of atoms at vacant sites
(comparison with the sphere model in film no. 1) are lim-
ited. It was only in recent years that concepts of the
real lattice structure could be developed as a result of
researches conducted by solid state physicists. They form
the basis for the theory of dislocations and, hence, for
the workability of metals.
Individual types of fault should
be presented and discussed sep-
arately by covering the film.
Film no. 5 provides the basis
for discussing the contents of
film no. 18 (process of deforma-
Film no. 6
To be able to explein the process of translation (deforma-
tion by shear - film no. 18) it is necessary to intro-
duce the term dislocation. Only edge dislocations will
be discussed here notwithstanding the fact that, in reality,
there zre numerous forms of dislocations such as screw dis-
locations, mixed-type dislocations, and so on. This rep-
resentation of dislocation requires that we confine our-
selves, for epistomological reasons, to few atoms and
lattice planes although, in actuality, thousands of atoms
are involved in it. A dislocation is a higher energy
(lower equilibrium) site surrounded by stress concentrations.
Be sure to point out the possibility of such stresses join-
ing so as to increase the overall stress level (cf. film
no. 19 that is concerned with the work hardening of copper).
Film no. 7
otching possibilities
Microscopic and metallographic examinations of metals and
alloys are not usually performed in all areas of voca-
tional education and training. However, it is necessary
to discuss problems associated with structural examinations.
This film can be used to compare theoretical knowledge
with practical results of structural examinations. “Students
should realize that results of structural examinations ob-
tained with the use of micrographs form the basis for ob-
taining new knowledge (e.g., in constitutional diagrams).
Shown in this film are, at a scale of 100 : 1, two micro-
graphs of pure copper etched using hydrochloric acid and
iron chloride, respectively.
It can be seen that etching results in the grain boundaries
and, later, the grain surfaces being attacked, with the
structural pattern thus being essentially dependent upon
the time of etching.
Contrast etching is also possible by using other and more
aggressive etchants. The action of etching agents can be
discussed by reference to film no. 2 (grain and grain bound-
Film no. 8
iacro- and micro-etching
This film can be used to demonstrate different methods of
examination. In metallogranhy, a distinction is made be-
tween macroexamination and microexamination depending upon
vhether a particular structure can be observed or identi-
fied with the naked eye or by means of a microscope. Shown
in fiim no. 8 are the images of an etched pure aluminum
ingot (at a scale of 1 : 1) and of a structural steel
microsection (at a scale of 100 : 1).
In the cese of the pure aluminum ingot, there can be seen
grain growth taking place as a result of cooling of the
small cast ingot from the outside in. Indentation results
from the decrease of volume. 'hereas the structural pat-
tern of pure aluminum allows only the kind of crystal forma-
tion to be seen, that of structural steel provides quali-
tative information about individual structural components.
Because of the larger number of nuclei of crystallization,
the structural constitution of mild steel is nearly uni-
form in all regions.
Film no. 8 can be discussed in connection with films nos.
à and 4 that are respectively concerned with grains and
grain boundaries and with crystal or grain growth.
Film no. 9
Coarse and fine grains
This film, which can be discussed in connection with film
no. 4 (crystal growth) and film no. 13 (curve of solidifi-
cation), enables instructors to explain the development
of different grain sizes. It includes two micrographs
of different grain size low-carbon steel etched using 3 %
alcoholic nitric acid, the scale being 100 : 1.
It is essential to discuss the effect of grain size upon
material properties (structure, behavior) with particular
reference to the causes of formation of coarse grains.
Film no. 10
Segregations in rimmed steel
The macrostructure of steel is greatly influenced by proc-
esses of segregation taking place during solidification
thereof. Such elements as phosphorus and sulfur show a
marked tendency toward segregating. Segregations present
in the original steel ingot are correspondingly modified
during metal working operations.
This film shows the images of two macroetches and of one
Baumann sulfur print of rimmed steel. The segregations
shown here are generally referred to as macro- and micro-
segregations, respectively. Be sure to give instructions
for use and fabrication (welding, drilling, corrosion, etc.)
of rimmed steels.
Film no. 11
Ketallurgical microscope
A metallurgical microscope can be used to examine ‘the kind,
proportion, size, form, and distribution of structural con-
Unlike transmitted-light microscopy of biological objects,
the metallurgical microscope is a reflected light micro-
Film no. 11 shows the "Epityp" 2 metallurgical microscope
made by VEB Carl Zeiss of Jena, G.D.R., and it is supple-
mented by a schematic representation of the optical path
in the microscope.
It is recommended that the applications of a metallurgical
microscope be explained during a visit to a metals testing
laboratory. The specimens examined using the microscope
should be ground, polished, and etched metal surrizces.
The contents of film no. 11 can be discussed in connection
with those of film no. 7 (etching possibilities), film no.
8 (macro- znd micro-etching), and film no. 9 (coarse and —
fine grains).
In so far as examinations performed using metallurgical
microscopes are concerned, it should be pointed out that
what counts is the results obtained rather than details
of methods of examination.
Film no. 12
Thermal analysis
This film can be used to explain metallographic analyses
of metals and alloys made with a view to determining melt-
ing points and intervals. It should be pointed out that
for a determination of solid state transformation points
use should preferably be made of a dilatometer which al-
lows changes in length to be measured, since the heat of
transformation is too low for a thermal analysis to be done.
Film no. 12 shows the arrangement of an electrically heated
furnace with the sample connected to the reference junction
which, in turn, is connected with the measuring instrument.
Also shown is a schematic diagram of a thermocouple with
measuring and reference junctions. Be sure to again explain
the operating principle of the thermocouple, if necessary.
It is in connection with the discussion of thermal analysis
that film no. 4 (crystal growth) and film no. 13 (curve of
solidification) can be touched upon and discussed, respec-
Film no. 13
Curve of solidification
This film can be used to again explain the process of
crystallization and, at the same time, learn and practice
the reading of diagrams. Also, this film can be used to-
gether with film no. 4 (crystal growth) to explain the
thermodynamic theory of fusion and solidification. The
film also shows individual phases of the process of crys-
tallization in a didactically simplified and graphic form
as we... as the curve of solidification of lead of which the
solidification temperature is 327°C. It should be pointed
out that such an 'ideal curve' can be obtained under lab-
oratory conditions only.
Film no. 14
This film shows, in a concentrated form, the solidifica-
tion curves of five alloys, the comstitutional diagram,
and the schematic representations of structural patterns.
Using this filn, it is possible to explain the plotting
of a constitutional diagram Irom cooling curves as well as
the constitutional or state changes taking place during
the cooling of individual alloys. Be sure to point out
that structures constitute what is known as a crystal
1% is essential that students should realize that consti-
tutional diagrams are stores of information on the states
of alloys in dependence upon both temperature and concen-
tration snd that they are required for making and heat-
treating alloys (concentration and temperature, respectivs-
It is recommended to present the in-
dividual images in their proper order
by covering portions of the film.
Film no. 15
Solid solutions
This film can be used to explain the constitutional dia-
gram of complete miscibility of alloy components in the
liquid and solid states, which is derived from the curves
of solidification of four alloys. from the diagram there
can be read changes taking place during the cooling and
heating of alloys in dependence upon both temperature and
The micrographs show equal-appearance solid solutions of
which the composition can be determined by chemical anal-
ysis only. By using the schematic representations for
substitutional and interstitial solid solutions, it is pos-
sible for this subject matter to be discussed and repeated
Depending upon the procedure
used by the instructor, portions
of the film can be covered one
after the other.
Film no. 16
Precipitations from solid solutions
This constitutional diagram with solid state miscibility
gaps and the cooling curve of an alloy with the correspond-
ing micrographs (in dependence upon temperature) can be
used to explain the process of hardening by precipitation
and the changes in the properties of alloys which are due
to dispersion. The schematic micrographs enable students
to arrive at a better understanding of the process of
precipitation and the change in solubility of an alloy with
decreasing temperature.
Students should realize that
properties of materials are
The contents of this film should
be discussed in steps correspond-
ing to individual stages of
-q 2m
Film no. 17
Stress-strain diagram
The objective of conveying knowledge of the workability
of materials is to enable students to interpret processes
proceeding within materials during working, for example.
To prepare students for a discussion of processes of defor-
mation, this stress-strain diagram of a soft type of steel
which includes the most important parameters as well-as
the elastic and plastic strain, respectively, can be used
to explain such characteristics as strength and strain.
This film can also be used for a discussion of materials
testing. It is essential that special importance be attach-
ed to the distinction between elastic and plastic strain
and elastic and plastic deformation.
The contents of film по. 17 should be discussed in connec-
tion with those of film no. 18 (process of deformation) and
film no. 19 (work hardening of copper).
Film no. 18
Process of deformation
Pilm no. 18 shows the stages of deformation of a lattice
portion in six individual images. Preferably, part of a
lattice model should be used to explain the terms elastic
and plastic deformation. Sliding in plastic deformation
occurs along a slip plane and is made possible by disloca-
tion. It is appropriate for the contents of film no. 6
(dislocation) to be discussed again in this context.
1t is essential that knowledge of the polycrystalline ma-
terial involved in the elementary process of sliding, which
was here acquired on a portion of the lattice only, should
be extended to cover the entire material.
The contents of this film should
be discussed in steps.
Film no. 19
work hardening of copper
Wiork hardening of metals can be regarded as being due to
an increase in aislocation density, the accumulation of
dislocations at obstacles, and the addition of concentra-
tions of stresses around individual dislocations. This
film can be used to discuss cold working results. It
shows the changes in tensile strength, elongation, and re-
duction in area of pure copper during wire drawing and en-
ables several curves to be compared. Intentional and un-
intentional changes in properties due Фо cold working should
be discussed in detail.
This film enables students to read and interpret the dia-
gram and compare the structures of soft and vork-hardened
copper wire.
Film no. 20
Recrystallization of copper
After having clarified the term work hardening, it is es-
sential to explain the terms recrystallization, cold work-
ing, hot working, and critical amount of deformation. Stu-
dents should reaiize that properties of materials have to
be influenced by increasing the temperature and causing
the structure to re-form in the solid state far below the
melting temperature.
This film shows the variation in tensile strength and
elongation as a function of the temperature of annealing.
The recrystallization range is supplemented by schematic
micrographs. The film allows to explain processes pro-
ceeding during recrystallization, desirable heating (e.g.,
annealing as an intermediate stage of wire drawing in order
to make possible additional drafts), and undesirable heat-
ing (e.g., in the soldering of contact springs which may
involve a loss of elasticity). Be sure to distinguish be-
tween cold and hot working in dependence upon the recrys-
tallization temperature of a metal (TR = 0.4 Ts in °K).
Also, point out the relationship between time of anneal-
ing and structure.
Film no. 21
lron-carbon diagram no. 1
The contents of films 21 through 26 have to be discussed
on the basis of the iron-carbon diagram described in the
literature. The forms of constitutional diagrams can be
assumed to be known. Since structures of alloys are to
be considered crystal aggregates, the modification of iron
can also be dealt with here.
This film shows, in the left and right halves thereof, the
cooling curve of pure iron and the iroan-carbon diagram up
to 2% of C (steel corner), respectively, as well as sche-
matic micrographs of steels having О, 0.4, 0.8, and 1.2 %
of C at temperatures below 723°C. Explain that the dif-
ferent solubility of iron modifications for carbon and the
consequent change in the temperature of transformation lead
to the iron-carbon diagram.
1% is essential that film no. 21
be discussed, step by step, in
connection with the contents of
film no. 24 (ferrite-austenite),
film no. 25 (primary and secondary
cementite), and film no. 26 (pearlite-
Film no. 22
lron-carbon diagram no. 2
This film can be used in vocational education and training.
It shows the complete iron-carbon diagram and a graphic
representation of the structural rectangle, which provides
information about the proportional percentages of structures
present under equilibrium conditions. essential to
point out that this diagram corresponds to a state of equi-
librium (extremely slow heating and cooling), whereas this
equilibrium is often disturbed in engineering and technical
After having discussed the contents of films 24 through 26,
it is appropriate to replace the phase designations in state
fields with the names of the respective structures. For
this, film no. 22 has to be covered with a blank film on
which the diagram is supplemented by dashed vertical lines
at 0.8, 2.06, and 4.3 % of C as well as by the names of
Film no. 23
Steel corner of the iron-carbon diagram
This representation forms the basis for all heat treat meth-
ods. 1+ is for this reason that knowledge of the iron-
carbon diagram with steel corner is of particular impor-
tance. To be able to correctly interpret all temperature-
dependent processes proceeding within a particular mate-
rial, it is recommended to discuss variations in the struc-
ture of steels with 0.4, 0.8, and 1.6 + of C.
By partly covering the film,
it is possible to draw the
student's attention to the
steel whose structure is be-
ing discussed.
Film no. 24
The original micrographs (200 : 1) in this film show the
ferritic and austenitic structures of iron. Since austenite
cannot generally "observed at room temperature, a high-alloy
austenitic chromium-nickel steel had to be used for examina-
Film no. 25
Primary and secondary cementite
This film shows the structure of primary cementite in lede-
burite (at a scale of 100 : 1) and the structure of secon-
dary cementite in pearlite (at a scale of 500 : 1).
Primary cementite is the bar- or needle-shaped structural
constituent of hypereutectic iron-carbon alloys. It is
from the melt
precipitated*in the form of platelike crystals along the
C - D line (iron-carbon diagram).
Secondary cementite is a structural constituent of hyper-
eutectic iron-carbon alloys appearing as grain-boundary
cementite or, in the case of higher carbon contents, as
needles in pearlite. lt is precipitated, along line E - 5,
from gamma-iron solid solutions because of diminishing
Film no. 26
This film shows the structures of both pearlite and lede-
burite (the scales being 500 : 1 and 100 : 1 for pearlite
and ledeburite, respectively). “hen showing the structures
of pearlite and ledeburite it is necessary to consider that
ledeburite (liquid-solid transition) is, in general, much
coarser in grain than pearlite (solid-solid transition).
The metallographic specimens were etched using 3 7% alcoholic
nitric acid.
Ledebu._te is a eutectic that is composed of austenite and
cementite. Pearlite is a lamellar conglomerate of ferrite
and cementite.
General science of metals 1
Crystal lattice
Unit cell
a = Lattice constant
a = 3:10'mm
Lattice plane
Space lattice
Crystal lattice
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General science of metals 2
Grain and grain boundary
AA 60664
Model Observable reality
Grain and grain boundary
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General science of metals 3
Unit cells
7)-Ре, Си, №
O(-Fe, Pb
body-centred cubic face-centred cubic
Unit cells
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General science of metals 4
Crystal growth
Rosenhain's diagram
Crystal growth
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General science of metals
Real structure
в ДД Iria
Ideal lattice
Rha Sie od
Era EE
Substitutional atoms Interstitial atoms
Real structure
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General science of metals 6
п + 1 atoms
bo ida:
a did
6-6 Món:
o-oo bdo aN,
e 6-00 6 UN Tdi
n atoms
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9. General science of metals
Etching possibilities
4 ¥ Г
Etching bringing out Contrast etching
grain boundaries in
Etching possibilities
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9 General science of metals
Macroetching and microetching
Pure aluminium ingot Mild structural steel
Ferrite and pearlite
Macroetching and microetching
MADE in GDR © Signograph
General science of metals
Coarse grain and fine grain
0,02 % C steel
i ы
31000 ym?
Coarse grain and fine grain
MADE in GDR O Signograph
General science of metals
Segregations in unkilled steel
Baumann cast
Oberhoffer etching
Heyn etching
Segregations in unkilled steel
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General science of metals 11
Metal microscope
A ” Epityp 2°
К. : :
e © М LA.
Specimen Eye - piece
Lamp Metal microscope
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General science of metals 12
Thermal analysis
e >=
7 `
Reference Measuring instrument
Electrically heated
furnace fat
with specimen SM: A
Measuring point
Thermal analysis
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General science of metals 13
Solidification curve
Arrest point
Solidification curve
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General science of metals 14
| \ | A+E
--m--m V ——- O
| +
Time A Concentration
A crystals
B crystals
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General science of metals 15
Mixed crystals
D © © @ © © © 9)
[ti 5
© © al
: Е Nera
5 LÉ X E
Time A Concentration B
Substitutional solution O @ ©) @
Mixed crystals
Interstitial solution
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General science of metals 16
Precipitations from mixed crystals
in ES
SE 8
° @
: Na NE +0 7 3 == €
el o | | pla
= OS a mi o
[o+E- +6 HH E ©
i O
Precipitations from mixed crystals
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General science of metals
Stress-strain curve
— Stress
premia — Om Strain
Stress - strain curve
© Signograph
General science of metals 18
Deforming process
undeformed elastically deformed relieved
elastically deformed elastically and relieved
plastically deformed
Deforming process
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General science of metals 19
Workhardening of copper
500 100
MPa 6 Yo
400 80
* ; y y
us —)¡ TT — eu, >
= 300 60 >
о Е
$ © 3
o =
e 200 40 К =
= Е
100 | \ 20
"м Ó
20 40 60 80%100
Degree of dressing
Workhardening of copper
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General science of metals 20
Recrystallization of copper
500 lia |
400 N Strain 0
N 3
300 || |
200 es | |
y Tensile strength 0
100 N
0 200 Tg 400 600 °C
J u Temperature
„== 20 =
| [or
Recrystallization of copper
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General science of metals 21
Iron-carbon diagram 1
Iron - carbon diagram
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General science of metals
Iron-carbon diagram 2
Iron - carbon diagram
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General science of metals 53
Steel corner-piece
800 A+sc
| a
P+ sc
600 |
12 16 %C 20
Steel corner - piece
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General science of metals
Ferrite -Austenite
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General science of metals
Primary and secondary cementite
\J \ 7
ней S М q ne E En |
= 3 S oy es ; м Do > Er] + L]
rene == МАМ, ANN SN
E 1 An L A ES y + x . я
= | A № SN *
> y WRAL? = e
Po sde
М |
A Te
A =
i \ |
ag Sy ve
px 3
р N
Primary and secondary cementite
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General science of metals
" VEER ai |, =
ут Ar = és a
Fa = 2
" e
“ a aaa В,
= des К
Pearlite - Ledeburite
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General science of metals
O Signograph
General science of metals
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