Investigation of Material and Mechanical Properties of Laser
Beam Welded (LBW) Laser Powder Bed Fusion (LPBF) and
Wrought Titanium Alloy Samples
A thesis submitted in fulfilment of the requirement for the degree of Master of Engineering
Ali Tamaddon
B. Sc. (Mechanical Engineering), Azad University, Tehran
P. E. (Institute of Engineers Australia), Canberra, ACT
School of Engineering
College of Science, Technology, Engineering and Mathematics
RMIT University
November 2021
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Declaration
I certify that except where due acknowledgement has been made, this research is that of the
author alone; the content of this research submission is the result of work which has been
carried out since the official commencement date of the approved research program; any
editorial work, paid or unpaid, carried out by a third party is acknowledged; and, ethics
procedures and guidelines have been followed.
In addition, I certify that this submission contains no material previously submitted for award
of any qualification at any other university or institution, unless approved for a joint-award
with another institution, and acknowledge that no part of this work will, in the future, be used
in a submission in my name, for any other qualification in any university or other tertiary
institution without the prior approval of the University, and where applicable, any partner
institution responsible for the joint-award of this degree.
I acknowledge that copyright of any published works contained within this thesis resides with
the copyright holder(s) of those works.
I give permission for the digital version of my research submission to be made available on
the web, via the University’s digital research repository, unless permission has been granted
by the University to restrict access for a period of time.
I acknowledge the support I have received for my research through the provision of an
Australian Government Research Training Program Scholarship.
Ali Tamaddon, 19/11/2021
Ali Tamaddon Page | iii
Acknowledgements:
This is to acknowledge the start of a new chapter in my life and a career in research.
I would like to express my sincere gratitude to Professor Sabu John and Distinguished
Professor Milan Brandt for their unequivocal support, guidance, and mentorship, which will
never be forgotten. Their invaluable knowledge and wisdom have been a beacon of reckoning
throughout these years. I would like to thank key RMIT staff that assisted me throughout this
research: Mr. Alan Jones of the Advanced Manufacturing Precinct (AMP) and Dr. Matthew
Field and Dr. Edwin Mayes from the RMIT Microscopy and Microanalysis Facility (RMMF) and
Dr. Wei Qian Song from the RMIT Bundoora East Material Testing Laboratories.
I would also like to thank my dearest son Mr. Daniel Tamaddon for his patience and
understanding during this period and Dr. Mohammad Mehdizadeh who encouraged me to
start this journey. A list of many good friends who supported me throughout this process
would be too long for this limited space and includes but is not limited to Dr. Joe Elambasseril
and Dr. Nabi Chowdhury to name a few.
Ali Tamaddon Page | iv
Table of Contents
Declaration .............................................................................................................................................. ii
Acknowledgements:............................................................................................................................... iii
Table of Contents ................................................................................................................................... iv
List of Tables ........................................................................................................................................ viii
List of Figures ......................................................................................................................................... ix
Abstract ................................................................................................................................................... 1
1. Introduction .................................................................................................................................... 3
1.1. Background ............................................................................................................................. 3
1.2. Motivation ............................................................................................................................... 5
1.3. Project Objectives ................................................................................................................... 6
1.3.1. Aim .......................................................................................................................................... 6
1.3.2. Research Questions ................................................................................................................ 7
1.3.3. Research Scope ....................................................................................................................... 7
1.4. Thesis Outline .......................................................................................................................... 8
1.5. References .............................................................................................................................. 9
2. Literature Review .............................................................................................................................. 10
2.1 Chapter overview .................................................................................................................. 10
2.2 Overview of additive manufacturing (AM) ........................................................................... 10
2.3 Metal additive manufacturing .............................................................................................. 13
2.4 Laser powder bed fusion (LPBF) ............................................................................................ 15
2.4.1 Powder feedstock ................................................................................................................. 17
2.4.2 Laser fusion ........................................................................................................................... 18
2.4.3 Build shielding gas ................................................................................................................. 20
2.5 Laser beam welding (LBW) .................................................................................................... 23
2.5.1 Introduction to lasers ............................................................................................................ 23
2.5.2 Disk lasers.............................................................................................................................. 24
2.5.3 Laser welding ........................................................................................................................ 24
2.6 Welding considerations ........................................................................................................ 28
2.7 Microscopy ............................................................................................................................ 29
2.8 Research Questions .............................................................................................................. 30
2.9 References ............................................................................................................................ 31
3. Materials and Methodology ......................................................................................................... 35
3.1 Introduction .......................................................................................................................... 35
3.2 First Phase: Pilot Samples ..................................................................................................... 35
3.2.1 Design of experiments .......................................................................................................... 35
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3.2.2 Material: ................................................................................................................................ 36
3.2.3 Fabrication of Laser Powder Bed Fusion (LPBF) parts .................................................. 38
3.2.4 Laser Beam Welding...................................................................................................... 41
3.2.5 Cross section and metallographic preparation ............................................................. 44
3.2.6 Microscopy (area, shape) .............................................................................................. 47
3.2.7 Weld porosity studies ................................................................................................... 47
3.2.8 EDS (chemical composition) .......................................................................................... 49
3.2.9 Microscopy (EBSD) ........................................................................................................ 50
3.2.10 Micro hardness ............................................................................................................. 52
3.3 Second Phase: Main Samples................................................................................................ 53
3.3.1 Design of experiments .......................................................................................................... 53
3.3.2 Fabrication of parts ............................................................................................................... 55
3.3.3 Pre-testing measurement and testing: ................................................................................. 59
3.3.4 Tensile test set up: ................................................................................................................ 59
3.3.5 Fatigue test set up: ............................................................................................................... 62
3.3.6 Post-test examinations: ........................................................................................................ 64
3.4 References ............................................................................................................................ 65
4. Results and Discussion .................................................................................................................. 66
4.1 Introduction .......................................................................................................................... 66
4.2 Pilot samples ......................................................................................................................... 66
4.2.1 Macroscopy ........................................................................................................................... 66
4.2.1.1 Weld appearance and comparison to AWI standards ...................................................... 66
4.2.2 Optical Microscopy ............................................................................................................... 68
4.2.2.1 Weld area measurement, shape, and penetration profile ............................................... 68
4.2.3 Scanning Electron Microscopy .............................................................................................. 73
4.2.3.1 EDS and chemical composition results ............................................................................. 73
4.2.3.2 Microstructure and EBSD results ...................................................................................... 75
4.2.4 Porosity analysis .................................................................................................................... 79
4.2.5 Hardness profile .................................................................................................................... 85
4.3 Main samples ........................................................................................................................ 89
4.3.1 Design of experiments .......................................................................................................... 89
4.3.2 Tensile tests .......................................................................................................................... 90
4.3.2.1 Tensile test setup .......................................................................................................... 90
4.3.2.2 Single piece wrought and LPBF tensile tests ................................................................. 90
4.3.2.3 Porosity analysis – Single piece wrought and LPBF ...................................................... 91
4.3.2.4 Welded wrought to LPBF assembly tensile tests ........................................................ 100