Szczecin, Poland
APPLYING MICROHARDNESS
TO MICROSTRUCTURE ANALYSIS
Małgorzata Garbiak
West Pomeranian University of Technology in Szczecin
Institute of Materials Science and Engineering
malgorzata.garbiak@zut.edu.pl
LMV’09 - Telć 11-13.11.2009
Presentation plan
¾
Hardness „finger prints”
¾
Indentation load
¾
Material tested – characteristics
¾
Measurements
¾
Analysis of results
¾
Histogram or direct aiming measurements
¾
Conclusions
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Hardness „finger prints”
Hardness density distribution
for a single phase material
M.Garbiak „Applying microhardness to microstructure analysis”
Hardness density distribution
for a two-phase material.
LMV’09 - Telć
Hardness density distribution analysis
Cast alloy #4
Pk=Gauss Amp 6 Peaks
Phase A
r 2 =0.999834
0.005
μ− structure A 2
0.0045
Hardness density distribution
SE=1.52802e-05 F=169492
0.004
274.6
μ− structure A 1
0.0035
0.003
μ− structure A 3
0.0025
0.002
0.0015
Phase B or
μ− structure B
374
0.001
0.0005
160.1
694.9
Phase C or
μ− structure C
500
μ− structure D
944.2
1330
0
0
Phase D or
1000
1500
Hardness [HV]
Christodoulou P., Garbiak M., Piekarski B.: Mat.Sc.Eng. A, 457(2007)350–367
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Average hardness and volume fraction
of the matrix and precipitates
1
2
3
4
5
9
7
8
9
As Cast
MVf
MH [HV]
MH [HV]
[%_weight] Weighed_Avg
Avg
86,3
289,5
238,9
97,7
284,4
231,1
97,1
232,9
243,1
90,3
304,3
269,5
97,0
298,9
279,8
77,9
297,0
203,6
90,7
253,9
239,1
96,0
340,3
263,3
88,6
273,4
228,6
MVf MH PVf -
Heat Treated
[%_weight
MVf
MH [HV]
MH [HV]
]
[%_weight] Weighed_Avg
Avg
13,7
90,7
289,2
258,8
2,3
93,3
252,3
225,3
2,9
92,8
248,9
187,8
9,7
70,8
340,6
299,1
3,0
99,0
233,7
231,5
22,1
71,4
350,6
228,8
9,3
88,3
337,1
310,2
4,0
94,1
311,5
302,5
11,4
94,5
312,1
257,1
PVf
[%_weight]
9,3
6,7
7,2
29,2
1,0
28,6
11,7
5,9
5,5
Matrix total volume fraction
Matrix hardness
Precipitates total volume fraction
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Alloy 3 - load 10G
8.9 μm
10 μm
Indentation load
Alloy 2 - load 5G
5.5 μm
Alloy 2 - load 10G
7.9 μm
10 μm
10 μm
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Indentation load
The smaller the indentation load
the more measured values of hardness
of single phase components
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Material tested
Austenitic Cast Steel – 0.3%C-18%Cr-30%Ni
Alloy no
1
2
3
4
5
6
7
8
9
Ti
0.83
1.00
0.05
0.70
0.03
1.07
0.53
0.30
0.68
Nb
1.75
0.03
1.84
3.00
0.03
1.59
2.80
0.55
2.06
Si
1.69
1.82
1.82
4.00
1.69
4.26
3.54
1.57
1.76
23 41
Stop
Alloy
51 23
Ti
Ti
1 mm
mm
DAS, mm
Nb
Nb
35
25
15
0.06
1.03
1.87
2.58
(Nb + Ti), wt%
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Microstructure
Heat treated
6
As-cast
2
900oC 300 h
3
900oC 300 h
10 μm
8
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Matrix
M23C6
10 μm
precipitates
dislocations
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Primary and eutectic precipitates
MC
Ni16(Ti,Nb)6Si7 + M23C6
Alloy 2
M23C6
G
TiC
G
M23C6
1 μm
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Microhardness of phase constituents
HV0.05
TiC
3000
(Nb,Ti)C
2800
2500
G
2000
M23C6
1500
1000
matrix
1400
1100
770
500
345
0
Average value of 10 measurements
Alloy 6
M.Garbiak „Applying microhardness to microstructure analysis”
10 μm
LMV’09 - Telć
Distinguishing of phases by their hardness
3000
HV
1500
1200
2200
1300
1000
1100
800
1400
TiC vs (Nb,Ti)C
(Nb,Ti)C vs G phase
G phase vs M23C6
TiC vs matrix
800
HV
600
Average
Standard deviation
Standard deviation * 1.96
400
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Random indentations
100 indentations under a load of 5G on cross sections of
as-cast and heat treated alloys
As - cast
BINARY HISTOGRAMS
Heat-treated
no changes occurred
reduce of hardness
increase of hardness
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Examples
Matrix – 294 HV
225HV – 14%
300HV – 67%
375HV – 7%
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Average weighted hardness of matrix
Alloy no
1
2
3
4
5
6
7
8
9
as-cast
294
277
246
291
291
310
260
343
272
annealed
295
247
247
353
252
331
318
315
280
Δ HV
1
-30
1
62
-39
21
58
-28
8
Changes in matrix microhardness ΔHV versus alloy chemistry:
ΔHV = -93.3+32.Si+19.7.Nb+45.4.Ti–22.4.Si.Ti
R2 = 0.999, F = 2902
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Influence of Nb and Ti on changes of matrix hardness ΔHV
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Matrix hardness
– how the average hardness value obtained from direct aiming
measurements can lead to misleading results
10 matrix indentations
Alloy no
1
2
3
4
5
6
7
8
9
as-cast
276
225
225
249
313
344
266
326
287
annealed
278
245
213
336
203
346
258
339
286
ΔHV
2
20
-12
87
-110
2
-8
13
-1
weighted matrix hardness
as-cast
294
277
246
291
291
310
260
343
272
annealed
295
247
247
353
252
331
318
315
280
ΔHV
1
-30
1
62
-39
21
58
-28
8
+ 23-89 HV
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
Conclusions
The random measurements of microhardness under the small loads enable,
among others, the following:
¾ determination of mean matrix hardness and then evaluation of the effect
of alloy chemistry on changes of the matrix hardness due to annealing,
¾ tracing changes in microstructure caused by phase transformations and
the processes of secondary precipitation through analysis of a quantitative
increase in the value of HV, corresponding to other phase constituents. A
possibility also exists to use hardness distribution as a tool for quantitative
evaluation of the phase constitutents present in alloy microstructure.
Increasing the sensitivity of measurements to improve the detectability of
individual phases seems to be a key problem
¾Due to high hardness of phases present in the examined cast steel and
their relatively small content, the applied method of microhardness
measurements not allows for further reduction of the load value and plotting
a multimodal histogram in which all the phase constituent would be
described. A solution might be here the random nanoindentation
measurements
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć
THANK YOU FOR ATTENTION
M.Garbiak „Applying microhardness to microstructure analysis”
LMV’09 - Telć