4th edition

1. Quantifying microstructural features
and finding structure-property
linkages in aging process of Al6061
ME8883 Materials Informatics
Ali Khosravani

2. Introduction
 Alloys in this group have
 high strength-to-weight ratio
 Good weldability
 good formability
 good corrosion resistance
Soft Strength increase Peak Strength Overaged
Solid
Solution
Coherent
Precipitates (β”)
Partially
Coherent(β’)
Incoherent
Precipitates(β)
 Application
 Aircraft fittings
 camera lens mounts
 electrical fittings and connectors
 brake pistons, hydraulic pistons
 valves and valve parts
 bike frames.
 Strengthen by Precipitation of
Mg2Si, higher levels of Mg2Si
leeds to higher strength

3. Microstructure
Microstructural features of impact
exist at different length scales
• Coherent GP zones and semi-coherent
precipitate particles (TEM or SEM)
 Volume fraction
 Size (nm)
 Aspect ratio
 Spacing (nm)
• Al-Fe-Si-type constituent particles (OM)
 Volume fraction
 Size (microns)
 Aspect ratio
 Spacing (microns)
• Grain structure, including degree of
recrystallization and texture (EBSD)
 Size (microns)
 Aspect ratio
 Texture

4. Mechanical Properties and microstructure
Precipitate hardening strengthen material
Mechanical Properties
is a result of :
 Precipitate Volume fraction
 Precipitate Size (nm)
 Precipitate Aspect ratio
 Precipitate Spacing (nm)
 Particle Volume fraction
 Particle Size (microns)
 Particle Aspect ratio
 Particle Spacing (microns)
 Grain structure
 Grain Size
 Grain Aspect ratio
 Texture
 Grain Boundary

5. Experiments

6. Mechanical testing
 Uniaxial Tensile Test
 Five tests were run for each condition.
 ASTM E8-13a (Round specimens with a diameter
and gage length of 0.25” of 1” respectively.
 The machine was run at a constant cross head
speed to achieve a strain rate of 0.005 in/in /s
Al 6061 Specimen
Type
Average Yield
Strength (ksi)
Average Ultimate
Tensile Strength (ksi)
400F HT 43.136 46.400
525F HT 26.022 33.188
650F HT 13.493 24.439
775F HT 8.633 20.321
AR RD 44.114 47.660

7. Microstructural Datasets
 EBSD
 75 scans and combined into
scan size of7x7 mm2
 4 μm resolution
 SEM
 10 BSE images at random
regions
 View field: 100x100 μm2
 Optical Microscope (OM)
 10 images at random regions
 View field: 800x600 μm2

8. EBSD dataset
• Grain size distribution
 Grain size distribution is
calculated based on number
of pixels in each grain.
• Grain aspect ratio distribution
 The aspect ratio is defined as
the length of the minor axis
divided by the length of the
major axis and thus ranges
from 0 to 1
Grain aspect ratio =
푏
푎

9. OM dataset
 Images were corrected and segmented
 Volume fraction, Size, Aspect ratio, and Spacing of particle
were measured
400F
Original Image Corrected Image Segmented Image
775F

10. Chord Length
 Calculating chord lengths row by row on x direction
and column by column in y directions on binary images
0 50 100 150 200 250 300 350 400 450 500
3
2
1
0
x 10
-4
Number of Pixels
Frequency
AR
400 F
525 F
650 F
775 F
 Performing this operation over 10 images

11.  TEM images required to provide
information about precipitate in
higher resolution and information
about precipitate/matrix interface
SEM dataset
 Images were segmented
 Volume fraction, Size, and Spacing of particle were measured

12. 2-Point Statistics vs Measures Values
2-point statistics contains all information
about particle size, aspect ratio, volume
fraction and their spacing.
PCA can be performed on 2-point statistic
instead of the calculated parameters (Size,
spacing, aspect ratio)
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-40 -20 0 20 40 60
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
PCA on 2-Point Statistics
-0.6
PC 1
PC 2
AR
400 F
525 F
650 F
775 F
-40 -20 0 20 40 60
PC 1
PC 3
0.1
0.08
0.06
0.04
0.02
0
-0.02
-0.04
-0.06
-0.08
-0.3 -0.2 -0.1 0 0.1 0.2
PC 1
PC 2
AR
400 F
525 F
650 F
775 F
0.03
0.02
0.01
0
-0.01
-0.02
-0.03
-0.3 -0.2 -0.1 0 0.1 0.2
PC 1
PC 3
PCA on Chord length(Particle
Spacing), Size, Aspect Ratio

13. 0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-30 -20 -10 0 10 20 30 40 50
PC 1
PC 2
AR
400 F
525 F
650 F
775 F
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-30 -20 -10 0 10 20 30 40 50
PC 1
PC 3
PCA on 2-Point Statistics

14. Averaging on Measured Values
 Image dimensions from each OM, EBSD,
and SEM datasets are different.
 The images were taken at random
regions on sample
To combine all Data together,
OM and SEM datasets need to
be averaged out
EBSD
OM
SEM

15. 2-point Statistics in quantifying each
microstructural features
00
f
r
150
200
0
250
0.04
0.03
0.02
0.03
0.02
0.03
0.02
150 200 250
0.04
0.03
0.02
0.01
150
200
250
150 200 -50 0 50
50
-50
2-point statistics contains all information
about particle size, aspect ratio, volume
fraction and their spacing.
PCA can be performed on 2-point statistic
instead of the calculated parameters (Size,
spacing, aspect ratio)
150
50
200
250
150
50
200
250
150
50
0
200
-50
150
50
0
200
250
150
50
200
250
150
50
0
200
-50
50
150
200
250
150
50
200
0
-50
250
-50 0 50
150
50
200
0
-50
0
-50
0
-50
0
-50
-50
0
-50
0.04
0.03
0.02
150
200
250
150 200 250
0.04
0.03
0.02
0.01
150
200
250
0.04
0.03
0.02
150 200 250
0.04
0.03
0.02
0.01
150
200
250
0.04
0.03
0.02
150 200 250
0.01
0.03
0.02
150
200
250
150 200 250
0.03
0.02
0.01
150
200
250
0.04
0.03
0.02
150 200 250
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0.03
0.02
0.01
150
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250
0.03
0.02
150 200 250
0.01
250
0.03
0.02
150
200
250
150 200 250
0.03
0.02
0.01
150
200
250
0.03
0.02
250
150 200 250
0.03
0.02
0.01
150
200
250
0.03
0.02
150 200 250
0.01
150
200
250
0.04
0.03
0.02
150 200 250
0.01
0.04
0.03
0.02
150 200 250
0.01
150
200
250
0.04
0.03
0.02
150 200 250
0.01
150
200
250
0.03
0.02
150 200 250
0.01
0.04
0.03
0.02
150 200 250
0.01
150
200
250
0.03
0.02
150 200 250
0.01
150
200
250
0.03
0.02
150 200 250
0.01
250
0.03
0.02
150 200 250
0.01
150
200
250
0.03
0.02
150 200 250
0.01
250
0.01
150 200 250
0.01
150 200 250
0.01
250
0.01
150 200 250
0.01
150 200 250
0.01
250
0.01
150 200 250
0.01
150 200 250
0.01
-50 0 50 -50 0 50 -50 0 50
-50 0 50 -50 0 50
-50 0 50 -50 0 50 -50 0 50

16. 0.1
0.05
0
-0.05
-0.1
-20 -10 0 10 20 30 40
0.06
0.04
0.02
0
-0.02
-0.04
-0.06
-0.08
-0.1
PCA on Average values from optical images (2-Point Statistics)
and EBSD values (Grain size, Grain aspect ratio)
-0.15
PC 1
PC 2
AR
400 F
525 F
650 F
775 F
-20 -10 0 10 20 30 40
PC 3
PC 1
Principal Component Analysis

17. Structure-property (Yield Strength) linkages
45
40
35
30
25
20
15
10
5
-20 0 20 40
Yield Strength (ksi)
PC 1
AR
400 F
525 F
650 F
775 F
45
40
35
30
25
20
15
10
5
-0.2 -0.1 0 0.1 0.2
Yield Strength (ksi)
PC 2
45
40
35
30
25
20
15
10
5
-0.1 -0.05 0 0.05 0.1
Yield Strength (ksi)
PC 3

18. Structure- property (Ultimate Tensile
Strength) linkages
50
45
40
35
30
25
20
-20 0 20 40
Ultimate Tensile Strength(ksi)
PC 1
AR
400 F
525 F
650 F
775 F
50
45
40
35
30
25
20
-0.2 -0.1 0 0.1 0.2
Ultimate Tensile Strength(ksi)
PC 2
50
45
40
35
30
25
20
-0.1 -0.05 0 0.05 0.1
Ultimate Tensile Strength(ksi)
PC 3

19. Future work
High Throughput Experiments
EBSD
OM
SEM
 Local properties
Measuring local properties
through nano- and miro-indentation
 Local microstructure
Collecting EBSD and OM
images at the same area, and
SEM images at the known
locations within marks

20. Acknowledgments
 Dr. Surya Kalidindi
 Dr. Tony Fast
 Jordan Weaver
 Jon Yabansu
 Ahmet Cecen
 Andrew Castillo