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118
J
anuary
2012
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A
rticle
Structure parameter
Standard number
ASTME112
GОSТ 5639
DIN 50601
Grain number
G
N
AE
= 2
G-1
G
= 10 – 2
log
2
l
_
G = 10 + 2
log
2
N–
L
G
m = 8 . 2
G
G
G =
log m
– 3
log 2
Number of grains in area of
1mm
2
1 inch
2
N
a
m =
2
n
100
2
m =
2
g
n
g
,
100
g
- magnification;
n
- number of grains
m =
2
n
100
m =
n
g
g
2
,
A
*)
g
- magnification;
n
- number of grains
N
ae
Average grain section area, mm
2
A–
a =
l
m
a =
l
m
Average grain diameter, mm
d–
d
m
=
l
m
d
m
=
l
m
Total length of line segments (chords),
mm
L
L
L
0
=
∑
L
Total number of grains cut by line
segment of length
L
(
L
0
), pcs
N
i
N
N
0
=
∑
N
Average length of chords (segments,
intersections) in the total length of the
test line, mm
l
_
d
L
=
L
N
–
L
S
=
L
0
N
0
Average number of nonequiaxed grains:
in 1 mm
2
in 1 mm
3
N–
A
= (
N
Al
N
At
N
Ap
)
1
–
3
-
-
-
N
V
= 0.7
N
x
N
y
N
z
-
х)
area of the circle confining the field of view
However they are not used in practice because of their laboriousness.
They are used exceptionally for scientific needs or in reclamation of
finished metal products.
Development of computerised analysis methods makes it possible
to reduce laboriousness of quantitative methods of assessment of
grain structures and obtain the most comprehensive information.
However the impossibility of making a reliable judgment on metal
anisotropy in finished products using the standard functioning
at present limits their use for a number of products made from
new heat-resistant and corrosion-resistant alloys prone to grain
anisotropy.
To make an objective assessment of the products made of materials
prone to grain anisotropy, a new method was developed for
quantitative assessment of parameters of spatial grain structures
by their two-dimensional image in metallographic sections. Based
on this method, an image analysis system
[7]
has been developed.
It includes a structural analysis package which ensures obtaining
of the following basic characteristics of the spatial grain structures
by their two-dimensional images visible in a microscope or
microphotography:
•
number of grains in a unit of area or volume
•
average and maximum diameters (in μm) of grains in a volume
•
numeric and graphic distribution of grain chords and diameters in
a plain section and grain diameters in a volume
•
areas and perimeters of all examined grains
Таble 1
:
Grain structure parameters determined by three standards