1. STUDY OF THE EFFECT OF AGING
CONDITION ON STRENGTH AND
HARDNESS OF 6063-T5 ALLOY
Supervised by : Dr. G.I.P. De Silva
Presented by : E.M.A.N. Ekanayaka
S.A.D.T. Dharmarathna

2. INTRODUCTION
 Aluminium - The most abundant metal in the earth
crust
• 8% by weight of the earth’s solid surface
 Properties - Durability, light weight, good extrudability
and surface finish
 Pure metal and the alloy used as alternatives for other
metals (ferrous and non-ferrous), ceramics and wood
 Sri Lankan demand
• Structural applications: Window and Door Frames,
Partitioning, L bars, U bars
2

3. ALUMEX (PVT) LTD.
Project was industrially focused on “Alumex”
Product: Extruded Aluminium articles
Raw material: 6063-T5 Aluminium alloy
3

4. ISSUES
Production cannot meet the present
increased demand
Relatively high cost of products
4

5. PRODUCTION PROCESS
Casting
Homogenizing
Extrusion
Age Hardening
Surface Treatments
5

6. REMEDY
Reduction of time in the Age
Hardening process
6

7. OBJECTIVES
To reduce the Age Hardening Time
To reduce the Energy Consumption
To upgrade the Mechanical Properties
7

8. LITERATURE REVIEW
8

9. 6063-T5 Aluminium alloy
 6063 Age Hardenable Aluminium alloy
• Main alloying elements: Mg (0.2 ~ 0.6 wt%)
Si (0.45 ~ 0.9 wt%)
 T5 - Cooled from an elevated temperature and
artificially aged
9

10. 6063-T5 Aluminium alloy
 Second Phase: Mg2Si
 Solid solubility of Mg2Si decreases from 1.85 wt. %
at the eutectic temperature of 595 C
 Al-Mg2Si quasi binary system forms
10

11. Age hardening
Strengthening a metal by introducing small particles of
another phase which barriers dislocations motion
Cutting through: Bowing and By pass:
When the precipitates are too When precipitates are too strong
small to be cut and inter-particle space
become large
 Maximum hardness is achieved if the precipitates can
resist cutting by dislocations, and are too close to
permit by-passing of dislocations.
11

12. The Age Hardening Process
Solution treatment
Age hardening treatment
SSSS
12

13. Al-Mg2Si quasi binary system
Sequence of precipitates in Al-Mg2Si
 GP zones – First form of precipitates (unstable)
Needle Shaped with the long axis along [100] of the matrix
13

14. Al-Mg2Si quasi binary system
Sequence of precipitates in Al-Mg2Si
 β΄ phase – Developed rod shape with Hexagonal crystal
structure
 Maximum hardness
14

15. Al-Mg2Si quasi binary system
Sequence of precipitates in Al-Mg2Si
 β phase - Equilibrium phase with FCC crystal structure
 Alloy is over aged – Hardness decreases
15

16. Al-Mg2Si quasi binary system
16

17. Closely Spaced Strong Large Increased
Fine Precipitates + Precipitates = Hardness
 Closely spaced fine precipitates
• Resist dislocation Bowing and By pass
 Strong large precipitates
• Resist cutting by dislocations
 This is called a Bimodal Precipitate Structure
17

18. CONCEPT
Two Step Aging Process
18

19. Homogeneous Nucleation of a Solute Cluster
r = radius of solute cluster
ΔG = free energy needed to form a spherical
cluster of radius r
GV = change in free energy per unit volume
σ = surface free energy per unit area
rc = critical radius of the cluster
19

20. Gibbs-Thompson equation
S = Amount of super saturation at a particular temperature
K = Temperature dependent constant ( K 1/ T )
rc= Critical radius of a cluster at the relevant temperature
 When T increases, rc increases
20

21.  At temp. T1 clusters nucleate and
grow - Size distribution: rmin – rmax
 When temp. is raised from T1 to T2,
critical radius is raised from rc1 to rc2
 If cluster radius r > rc2, the cluster will
survive and continue to grow
 If cluster radius r < rc2, the cluster will
be unstable and will dissolve. But
re-nucleation may occur.
 This results a Bimodal Precipitate
Structure with both closely spaced
fine precipitates + strong large
precipitates, which results better
Mechanical Properties.
21

22. Industrially Practiced Age Hardening Process
Solution treatment
Age hardening treatment
Process was re-performed within the laboratory
Results were used as reference values
•Measured Hardness(HV) – 47.05
•Total Time (Age Hardening) – 270 min 22

23. Parameters Varied During the Process
Temperature (oC)
T2
T1
Time (min)
t1 t2 t3 t4 t5
 1st step temperature - T1
 Time to reach the 1st step temperature - t1
 Soaking time in the 1st temperature - t2
 2nd step temperature - T2
 Time to reach the 2nd step temperature - t3
 Soaking time in the 2nd temperature – t4
23

24. LIMITATIONS
Furnace Limitation
• The industrially acceptable range: 150oC to 250oC
Energy Consumption
Total Time Consumption
• Below 270 min
24

25. CONSTANTS
 Time to reach the 1st step temperature: t1
• 60 minutes
 2nd step temperature: T2
• 225oC
 Time to reach the 2nd step temperature: t3
• 30 minutes
Temperature (oC)
T2
T1
t1 t2 t3 t4 t5 Time (min) 25

26. STAGE 1 - VARIABLES
 1st step temperature: T1
• Altered within150oC-200oC
 Soaking time in the 1st temperature: t2
• Varied from 45 min- 90 min for each set of temperatures
 Soaking time in the 2nd temperature: t4
• Varied Combinations-15 min and 30 min
Temperature (oC)
T2
T1
t1 t2 t3 t4 t5 Time (min) 26

27.  All Specimens were Solution Treated
• At 540oC for 3 hours
• To remove age hardening imposed
• Dissolve all precipitates
Muffle Furnace
27

28.  A set of combinations among the above
variables were developed
 Heat treatments were performed using the
Super C furnace for 2 samples per combination.
Super C Furnace
28

29.  Hardness was tested using Vickers Hardness
tester
• 3 per sample 6 per combination
• Average was recorded
 Optimum suitable parameters determined using
hardness obtained
Vickers Hardness Tester 29

30. Aging Time and Temperature Combinations
Temperature (oC)
T2
t4 – maintained as 15 min T1
T1 – varied from 150oC to 200oC
t1 t2 t3 t4 t5 Time (min)
1st step 2nd step Hardness
Temperature Time Temperature Time (HV)
150oC 60 min 225oC 15 min 37.85
150oC 90 min 225oC 15 min 38.25
175oC 45 min 225oC 15 min 39.10
175oC 60 min 225oC 15 min 41.68
175oC 75 min 225oC 15 min 47.58
175oC 90 min 225oC 15 min 45.93
200oC 60 min 225oC 15 min 35.05
200oC 90 min 225oC 15 min 37.87
Hardness – Not Satisfactory 30

31. 31

32. Temperature (oC)
T2
t4 – maintained as 30 min
T1
T1 – varied from 150oC to 200oC
t1 t2 t3 t4 t5 Time (min)
1st step 2nd step Hardness
Temperature Time Temperature Time (HV)
150oC 60 min 225oC 30 min 41.47
150oC 90 min 225oC 30 min 41.25
175oC 45 min 225oC 30 min 40.92
175oC 60 min 225oC 30 min 51.68
175oC 75 min 225oC 30 min 52.05
175oC 90 min 225oC 30 min 43.78
200oC 60 min 225oC 30 min 36.42
200oC 90 min 225oC 30 min 40.62
Reference Hardness (HV) – 47.05
32

33. DERIVATION
 1st Step Temperature (T1) : 175oC
 1st Step Soaking Time (t2) : 60 min
Rejections
• 150oC – Low hardness in acceptable time duration
• 200oC – Higher energy consumption
33

34. Current Status
 1st step temperature : 175oC
 Time to reach the 1st step temperature : 60 min
 Soaking time in the 1st temperature : 60 min
 2nd step temperature : 225oC
 Time to reach the 2nd step temperature : 30 min
Temperature (oC)
225
175
60 60 30 t4 30 Time (min)
34

35. STAGE 2
 2nd step soaking time “t4” was altered
• 0 ~ 60 min – 10 min intervals
 Differentsets of combinations were developed
 Samples prepared as standard tensile test
specimens
14mm
66 mm
(Gauge Length) 1.72mm
150 mm
Tensile Test Sample
35

36.  Heat Treatment - Super C
• 2 specimens per combination
 Hardness - Vickers Hardness Tester
• 3 per sample 6 per combination
• Average was recorded
 Tensile Strength – Tensile Testing Machine
Tensometer 36

37. Combinations and Results for varied “t4”
Heat Treatment Hardness Tensile Strength
Sample no t4 (min)
1st Step 2nd Step (HV) (N/mm2)
1 Reference _ 47.05 228.41
2 175oC - 60 min 225 oC - 0 min 0 45.08 170.27
3 175oC - 60 min 225 oC - 10 min 10 45.38 182.72
4 175oC - 60 min 225 oC - 20 min 20 46.83 199.34
5 175oC - 60 min 225 oC - 30 min 30 49.13 228.41
6 175oC - 60 min 225 oC - 40 min 40 51.10 240.86
7 175oC - 60 min 225 oC - 50 min 50 47.88 240.86
8 175oC - 60 min 225 oC - 60 min 60 45.33 232.56
37

38. Graph of Hardness Vs “t4” value
57.00
52.00
51.10
49.13 47.88
Hardness (HV)
47.00
47.05
46.83
45.33
45.08 45.38
42.00
37.00
32.00
0 10 20 30 40 50 60
t4 value (min)
38

39. Graph of Strength Vs “t4” value
260.00
240.86 240.86
240.00
232.56
Tensile Strength (N/mm2)
220.00 228.41
228.41
200.00
199.34
180.00
182.72
170.27
160.00
140.00
120.00
100.00
0 10 20 30 40 50 60
t4 value (min)
39

40. Energy Comparison
 Theoretically
• Absorbed heat energy (E) = mc
E= Heat energy
m = Mass of samples
c = Specific Heat Capacity
= Temperature Difference
• Since m and c are constant
• Energy Ratios = Ratio of areas under the graphs
Temperature (oC)
Time (min) 40

41. EFFECTIVENESS – Varied “t4”
Heat Treatment Total Time % Time % Energy
Sample no t4 (min)
1st Step 2nd Step (min) Saving Saving
_
1 Reference 270 0 0
2 175oC - 60 min 225oC- 0 min 0 180 33.33 45.59
3 175oC - 60 min 225oC- 10 min 10 190 29.63 39.96
4 175oC - 60 min 225oC- 20 min 20 200 25.93 34.33
5 175oC - 60 min 225oC- 30 min 30 210 22.22 28.71
6 175oC - 60 min 225oC- 40 min 40 220 18.52 23.08
7 175oC - 60 min 225oC- 50 min 50 230 14.81 17.45
8 175oC - 60 min 225oC- 60 min 60 240 11.11 11.82
Optimum was selected considering above results
41

42. Developed Process Process at Alumex
225
205
Temperature (oC)
Temperature (oC)
175
Time (min) Time (min)
60 60 30 40 30 90 150 30
Hardness (HV) = 51.10 Hardness (HV) = 47.05
Tensile Strength (N/mm2) = 240.86 Tensile Strength (N/mm2) = 228.41
Total Time (min) = 220 Total Time (min) = 270
42

43. Microstructure Observations
 Microstructure
• Selected sample and reference
• Viewed using Metallurgical microscope (X200)
• Idea about grain size
Metallurgical Microscope
43

44. Microstructure Observation
After optimized Two Step Aging Treatment
Polishing Agent: Polycrystalline Diamond Powder
Etchant: 5% HNO3 + 2% HF Solution
After “Alumex” Practiced Aging Treatment
Polishing Agent: Polycrystalline Diamond Powder
Etchant: 5% HNO3 + 2% HF Solution
44

45. PROGRESS
Temperature (oC)
225
175
60 60 30 40 30 Time (min)
Property / parameter Practiced Process Developed Process
Hardness (HV) 47.05 51.10
Tensile Strength (N/mm2) 228.41 240.86
Total Time (min) 270 220
Time Saving (min) _ 50
% Time Saving _ 18.52
% Energy Saving _ 23.08
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46. CONCLUSION
 Considering Production Rate, Production Cost and
Enhanced Mechanical Properties the following Age
Hardening Treatment is recommended.
Temperature (oC)
225
175
60 60 30 40 30 Time (min)
46

47. THANK YOU
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