The document summarizes a study on improving the strength and hardness of 6063-T5 aluminum alloy through optimizing the aging process. Through experimenting with different aging temperatures and times, researchers found that a two-step aging process of 175°C for 60 minutes followed by 225°C for 40 minutes maximized hardness and tensile strength while reducing aging time by 18.5% and energy consumption by 23.1% compared to the industry standard process. Microstructure analysis showed finer precipitates in the optimized process, explaining the improved mechanical properties. The study demonstrated that a two-step aging treatment can enhance aluminum alloy properties in a more efficient manner.

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
5
Casting
Homogenizing
Extrusion
Age Hardening
Surface Treatments

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

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

13. Al-Mg2Si quasi binary system
 GP zones – First form of precipitates (unstable)
Needle Shaped with the long axis along [100] of the matrix
Sequence of precipitates in Al-Mg2Si
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 fine precipitates
• Resist dislocation Bowing and By pass
 Strong large precipitates
• Resist cutting by dislocations
 This is called a Bimodal Precipitate Structure
17
Closely Spaced
Fine Precipitates
Strong Large
Precipitates
Increased
Hardness+ =

18. CONCEPT
Two Step Aging Process
18

19. 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

20. Gibbs-Thompson equation
S = Amount of super saturation at a particular temperature
K = Temperature dependent constant ( K a 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
22
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

23. Parameters Varied During the Process
 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
T2
T1
t5t4t3t2t1
Temperature (oC)
Time (min)

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
25
T2
T1
t5t4t3t2t1
Temperature (oC)
Time (min)

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
26
T2
T1
t5t4t3t2t1
Temperature (oC)
Time (min)

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

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.
28
Super C Furnace

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

30. Aging Time and Temperature Combinations
30
1st step 2nd step Hardness
(HV)Temperature Time Temperature Time
150o
C 60 min 225o
C 15 min 37.85
150o
C 90 min 225o
C 15 min 38.25
175o
C 45 min 225o
C 15 min 39.10
175o
C 60 min 225o
C 15 min 41.68
175o
C 75 min 225o
C 15 min 47.58
175o
C 90 min 225o
C 15 min 45.93
200o
C 60 min 225o
C 15 min 35.05
200o
C 90 min 225o
C 15 min 37.87
t4 – maintained as 15 min
T1 – varied from 150o
C to 200o
C
T2
T1
t5t4t3t2t1
Temperature(oC)
Time (min)
Hardness – Not Satisfactory

31. 31

32. 32
t4 – maintained as 30 min
T1 – varied from 150o
C to 200o
C
T2
T1
t5t4t3t2t1
Temperature(oC)
Time (min)
1st step 2nd step
Hardness
(HV)Temperature Time Temperature Time
150o
C 60 min 225o
C 30 min 41.47
150o
C 90 min 225o
C 30 min 41.25
175o
C 45 min 225o
C 30 min 40.92
175o
C 60 min 225o
C 30 min 51.68
175o
C 75 min 225o
C 30 min 52.05
175o
C 90 min 225o
C 30 min 43.78
200o
C 60 min 225o
C 30 min 36.42
200o
C 90 min 225o
C 30 min 40.62
Reference Hardness (HV) – 47.05

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

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
34
225
175
30t4306060
Temperature(oC)
Time (min)

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

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
36
Tensometer

37. Combinations and Results for varied “t4”
37
Sample no
Heat Treatment
t4 (min)
Hardness
(HV)
Tensile Strength
(N/mm2)1st Step 2nd Step
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

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

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

40. 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
40
Temperature (oC)
Time (min)
Energy Comparison

41. EFFECTIVENESS – Varied “t4”
41
Sample no
Heat Treatment
t4 (min)
Total Time
(min)
% Time
Saving
% Energy
Saving1st Step 2nd Step
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

42. 42
225
175
3040306060
Temperature(oC)
Time (min)
205
90
Temperature(oC)
Time (min)
30150
Developed Process Process at Alumex
Hardness (HV) = 51.10
Tensile Strength (N/mm2) = 240.86
Total Time (min) = 220
Hardness (HV) = 47.05
Tensile Strength (N/mm2) = 228.41
Total Time (min) = 270

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

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

45. 45
225
175
3040306060
Temperature(oC)
Time (min)
PROGRESS
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

46. 46
CONCLUSION
 Considering Production Rate, Production Cost and
Enhanced Mechanical Properties the following Age
Hardening Treatment is recommended.
225
175
3040306060
Temperature(oC)
Time (min)

47. THANK YOU
47