La/ d o n / ^ / J ^ 
2 1 
Enhancement of Mechanical Properties in the Heat 
Affected Zone of A A 5083 Weld Joints 
W. U. S. Mirihanage 
"'''-v.'z-y 
T h i s T h e s i s w a s s u b m i t t e d to t h e D e p a r t m e n t o f M a t e r i a l s E n g i n e e r i n g o f t h e 
U n i v e r s i t y o f M o r a t u w a i n p a r t i a l f u l f i l l m e n t o f the r e q u i r e m e n t s f o r t h e D e g r e e o f 
M a s t e r o f P h i l o s o p h y . 
8 3 8 1 1 
University of Moratuwa //tS^^ 
D e p a r t m e n t o f M a t e r i a l s E n g i n e e r i n g G ^ y 
U n i v e r s i t y o f M o r a t u w a , S r i L a n k a . 
1 5 - 0 5 - 2 0 0 5 0 3 6 1 / 
83811 
D E C L A R A T I O N 
I certify that the Thesis with the title " Enhancement of Mechanical Properties in 
the Heat Affected Zone of A A 5083 Weld Joints " is entirely my own work. It has 
not been accepted for any degree and it is not being submitted for any other degree. 
Candidate 
W. U. S. Mirihanage Signature 
Date 
Supervisor 
Dr. N . Munasinghe Signature 
A C K N O W L E D G M E N T 
Initially, I would like to thank my supervisor Dr. Nanda Munasinghe for his guidance, 
support and encouragement. Then, to Dr. Rohan Thitagala for his kind and supportive 
advices, Commander Lalith Alahakone and Lieutenant Senaka Kumarasinghe of Sri 
Lanka Navy for their support and co-operation had given to my studies about the weld 
defects in marine applications. 
In addition to that, 1 like to express my gratitude to Dr. S. U. Adikary and all the 
academic and non-academic staff of the Department of Materials Engineering, University 
of Moratuwa for their help and contribution for my research. 
Same time I appreciate and thank to Prof. Jayasinghe of Engineering Design Center, 
CAD/CAM/CAE and workshop staff of Department of Mechanical Engineering at 
University of Moratuwa, Department of Botany, University of Colombo and Colombo 
Dockyard Ltd. staff for their support and assistance. 
I must be indebted to Asian Development Bank funded personal development project for 
their awarding of a full scholarship for entire studies. 
At last but not least, it is indeed to thank my mother, father and my wife Nadeesha for 
their encouragement, support and sacrifice. 
Wajira U. S. Mirihanage 
Department of Materials Engineering, 
University of Moratuawa. 
15 t h March 2005 
Acknowledgement in 
ABSTRACT 
Decline of Mechanical properties were observed at the Heat Affected Zone (HAZ) of the 
Gas Metallic Arc Weld (GMAW) joints of the Aluminium Alloy (AA) 5083. It was 
concerned as a direct effect of the weld thermal cycle on the work hardened material. 
Experimental efforts were aimed to set up a post welding procedure to recover this 
decline of properties. Presence of the Silicon in AA 5083 was significant in the 
experimental considerations due to its tendency of forming M g 2 S i precipitates at 
intensified temperatures. A series of mechanical and microstructure observations were 
done to evaluate the effectiveness of the post weld heat treatment, with the AA 5083. 
According to the experimental results heat treatment at 473K for 10 minutes produced the 
most effective improvement of mechanical properties at the HAZ of weld joint. 
Abstract ii 
CONTENT 
Declaration i 
Abstract ii 
Acknowledgement iii 
Content iv 
List of Figures vi 
1. Introduction 01 
2. Literature Review 02 
2.1 Aluminum - Introduction to the Material 02 
2.2 Aluminum - History and Extraction Process 03 
2.3 Classification of Aluminum and Aluminum alloys 05 
2.4 Engineering Applications of Aluminum and Aluminum alloys II 
2.5 Concerning Factors in Application of Aluminum Alloys 16 
2.6 Characteristics of AA 5083 and other 5xxx series alloys 20 
2.7 Welding of Aluminum alloys 24 
2.6 Gas Metallic Arc Welding(GMAW) Process 28 
3. Problem Analysis 33 
3.1 Defect analysis of AA 5083 GMAW joints 33 
3.2 Material Characteristics of AA 5083 welded joints 38 
4. Experimental Results 39 
4.1 Materials Testing Equipments 39 
4.2 Chemical composition & Mechanical properties of AA 5083 43 
4.3 Variation of mechanical Properties along the AA 5083 G M A W joint 45 
Content 
4.4 Affects of heat on hardness of AA 5083 48 
4.5 Variation in Mechanical Properties of Heat 
Treated AA 5083 GMAW Joints 49 
4.6 Microstructure of AA 5083 (as received condition) 61 
4.7 Microstructure variation along the AA 5083 GMAW joint 63 
4.8 Affects of Heat on AA 5083 microstructure 65 
4.9 Microstructure variations on heat treated 
AA 5083 GMAWjoin t s 66 
4.10 Experimental Limitations and further work 67 
5. Discussion 68 
5.1 Weld Thermal Cycle 68 
5.2 Improvement Properties HAZ by Heat Treatment 69 
5.3 Metallurgical Approach to Behavior of Precipitates 70 
5.4 Practical Utilization of Experimental Results and further work 75 
6. Conclusion 76 
7. References 77 
8. Annexes 80 
Content 
LIST OF FIGURES AND TABLES 
Figures 
Fig. No. 2.1 FCC structure of Aluminum unit cell 02 
Fig. No. 2.2 Aluminum extraction process 05 
Fig. No. 2.3 Gas Metallic Arc Welding Diagram 29 
Fig. No. 3.1 Insufficient weld penetration 33 
Fig. No. 3.2 Undercut 34 
Fig. No. 3.3 Reinforcement too high 34 
Fig. No. 3.4 Too much root penetration 34 
Fig. No. 3.5 Edge misalignment 35 
Fig. No. 3.6 Porosity at aluminum weld joint 35 
Fig. No. 3.7.(a)Single pores 36 
Fig. No. 3.7.(b)Pore clusters 36 
Fig. No. 3.7.(c)Liner porosity 36 
Fig. No. 4.1 GMAW welding plant 39 
Fig. No. 4.2 Hounsfield Tensometer 39 
Fig. No. 4.3 Microhardness Tester 40 
Fig. No. 4.4 Vickers Hardness Tester 40 
Fig. No. 4.5 (a)Grinding equipment 41 
Fig. No. 4.5 (b) Polishers 41 
Fig. No. 4.6 Metallurgical Microscope 42 
Fig. No. 4.7 Scanning Electron Microscope 42 
Fig. No. 4.8 Atomic Absorption Spectrometer 42 
Fig. No. 4.9 AA 5083 Stress - Strain curve of AA 5083 45 
Fig. No. 4.10 Variation of hardness along the AA 5083 GMAW joint 46 
Fig. No. 4.11 Tensile samples to test weld joint properties 47 
Fig. No. 4.12 Stress-Strain diagrams for Zones of AA 5083 weld joint 47 
List of Figures and Tables 
Fig. No. 4.13 Hardness variation of Treated AA 5083 samples 49 
Fig. No. 4.14 Hardness testing profile of weld joint 51 
Fig. No. 4.15 Change of micro hardness of the cross section of the 
weld treated for 5 minutes at Different Temperatures 
51 
# 
Fig. No. 4.16 Change of micro hardness of the cross section of the weld 
treated for 10 minutes at different Temperatures 
52 
Fig. No. 4.17 Change of micro hardness of the cross section of the 
weld treated for 15 minutes at different Temperatures 
52 
Fig. No. 4.18 Change of micro hardness of the cross section of the 
weld treated for at 473 K for different time intervals 
53 
Fig. No. 4.19 Change of micro hardness of the cross section of the 
weld treated for at 473 K for different time intervals 
53 
Fig. No. 4.20 Tensile test sample preparation for Weld metal 55 
Fig. No. 4.21 Stress-Strain curve for treated samples 56 
Fig. No. 4.22 Tensile samples obtain from the HAZ of heat treated 57 
> specimens 
Fig. No. 4.23 Change of Tensile Properties of the Heat Affected Zone 
treated for 5 Minutes 
58 
Fig. No. 4.24 Change of Tensile Properties of the Weld Metal Zone 
treated for 10 Minutes 
59 
Fig. No. 4.25 Change of Tensile Properties of the Heat Affected Zone 
treated for 15 Minutes 
59 
Fig. No. 4.26 Change of tensile properties of the Heat Affected Zone 
soaked at 473 K 
60 
Fig. No. 4.27 Change of tensile properties of the Heat Affected Zone 
treated at 673 K 
60 
Fig. No. 4.28 Micro Structure of AA 5083 etched after different etchants 62 
Fig. No. 4.29 Microstructure Examination Points in weld joint 63 
Fig. No. 4.30 Macro Photograph of AA 5083 Weld joint Cross Section 63 
Fig. No. 4.31 Microstructure Photographs of Various Points of 
AA 5083 Weld Joint 
64 
Fig. No. 4.32 AA 5083 Heat Treated for Different Soaking Temperatures 65 
Fig. No. 4.33 Microstructure - HAZ of AA 5083 Heat Treated at 473K 66 
Fig. No. 4.34 Microstructure - HAZ of AA 5083 Heat Treated at 673K 66 
List of Figures and Tables 
• 
Fig. No. 5.1 Temperature distribution during welding 
Fig. No. 5.2 Linear Relationship of Radius of the 
Precipitate and Soaking time 
Fig. No. 5.3 Movement of dislocations through precipitates 
Fig. No. 5.4 Average micro hardness vs. treated time 
68 
72 
73 
74 
Tables 
Table 4.1 .a) Chemical composition of AA 5083 - Experimental values 43 
Table4.1.b) Chemical composition of AA 5083 - Values by standards 43 
Table 4.2 Comparison of Vickers and Microhardness Hardness 44 
values of AA 5083 
Table 4.3 Average hardness after heat treatment of AA 5083 base metal 48 
Table 4.4 Heat treatment parameters for hardness testing 50 
Table 4.5 Heat treatment parameters for tensile testing 57 
Table 4.6 Chemical Attacks on Intermetallic Phases in AA 5083 61 
List of Figures and Tables viii