Superior energy absorption of continuously graded microlattices by electron beam additive manufacturing

ABSTRACT

Electron beam melted (EBM) Ti-6Al-4V functionally graded materials (FGM) with continuously graded densities are investigated for dimensional accuracy, compressive properties, fractography and build direction effect in comparison to uniform density counterparts of the same volume. It is found that FGMs exhibit progressive layer-by-layer deformation mode regardless of unit cell designs and build direction. This deformation behavior is highly favourable for uni-directional impact absorption applications compared to uniform density counterparts with random or diagonal failure. Overall, the EBM-built FGM exhibits superior energy absorption than counterparts of uniform density. Significant improvement in the quasi-elastic gradient and energy absorption is obtained by changing the build direction for specific designs. Compared with other FGM or uniform density lattice structures from the literature, the energy absorption of lattice structures with lower relative density could outperform those with higher relative density by changing the unit cell design or density profile.

KEYWORDS:

• Functionally graded material
• additive manufacturing
• electron beam melting
• lattice structure
• compressive properties

Acknowledgements

The work was financially supported by A*STAR Industrial Additive Manufacturing Program: Work Package 3 (Electron Beam Melting, grant number 1325504103) and SIMTech-NTU Joint Laboratory (3D Additive Manufacturing) Project Fund.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Agency for Science, Technology and Research: [grant number 1325504103].

Notes on contributors

Sing Ying Choy

Ms. Sing Ying Choy is a Research Engineer in A*STAR SIMTech. She has working experience with both industries and research institutes. The roles she worked before in industries include business development for industrial waste treatment, environmental compliance of electrical and electronic products. In the field of R&D, she involved in various research related to solid waste treatment as well as additive manufacturing. With years of research experience, she has published several papers in international journals and conferences in the areas of environmental technologies and additive manufacturing.

Chen-Nan Sun

Dr. Chen-Nan Sun is a Scientist with the 3D Additive Manufacturing Team at SIMTech. He received his Ph.D. degree in Electrical and Computer Engineering from the University of Virginia, USA. Dr Sun worked for Taiwan Semiconductor Manufacturing Company (TSMC), Taiwan, and National Institute of Aerospace (NIA), USA, before moving to Singapore in 2011. His research interests include laser processing of materials, electronic materials, and semiconductor device fabrication. Dr Sun has led the development of selective laser melting (SLM) technology at SIMTech for a variety of industrial applications. He has published one book chapter and over 75 international journal and conference papers on 3D additive manufacturing processes and materials.

Wai Jack Sin

Mr. Wai Jack Sin is a Research Engineer with the 3D Additive Manufacturing Team at SIMTech. He is a graduate from Nanyang Technological University with a Bachelor's in Engineering (Mechanical Engineering). His research interest includes electron beam and laser processing of materials, metallic powder production and analysis, and post-processing of AM components. Sin has had R&D experience with electron beam melting (EBM) and selective laser melting (SLM) technologies, working with industry partners in the realization of metallic AM adoption in manufacturing industry. In his time in SIMTech, he has authored and co-authored several journal publications and conference papers for both EBM and SLM research.

Kah Fai Leong

Kah Fai Leong is an associate professor in the School of Mechanical and Production Engineering, Nanyang Technological University. He obtained his B.Eng. (Mech.) with Honours from the National University of Singapore in 1981 and M.Sc. degrees in Engineering Product Design and Mechanical Engineering, from Stanford University in 1987. Prior to joining NTU, he has worked several years as a product development engineer and designer in the Singapore electronics industries. He was awarded the Merit Award in 1994 and Distinguished Award in 1997 for his contributions to the national standardisation program. He has co-authored four books, published several book chapters and more than 100 papers in international journals, conferences, and seminars in these areas. He has been invited as a keynote speaker for a number of premier conferences and has acted as reviewers for several journals, including Trends in Biotechnology, Biomaterials, International Journal of Product Development, etc. He is also the winner of the Emerald Highly Commended Award in Emerald Literati Network Awards for Excellence 2007 for his paper in Rapid Prototyping Journal,

Pei-Chen Su

Dr. Pei-Chen Su is an associate professor in the School of Mechanical & Aerospace Engineering, Nanyang Technological University. Dr. Su's research interests are in applying microsystem technologies, nanoscale thin film materials engineering, and nano-patterning technologies at the interface of energy conversion devices, specifically fuel cells. She pioneered in development of high power density nano thin film oxide fuel cells at low operating temperature and keeps leading cell performance in the literature. Her research interests include low temperature solid oxide fuel cells, micro/nano fabrication, nanoionics, and thin film energy materials. Her research group focuses on developing new electrode and electrolyte materials and nano-engineering of cell components via thin film deposition technologies, design and fabrication of scalable micro-SOFCs, and study of reaction kinetics between cathode and nano thin film electrolyte interface, all together with an ultimate goal of commercialising a practical device for SOFCs below 500°C.

Jun Wei

Dr. Jun Wei is a professor at Harbin Institute of Technology (Shenzhen). Concurrently he is the University President Assistant, Director of Shenzhen Key Laboratory on Flexible and Printed Electronics Technology, Director of Flexible and Printed Electronics Center. Before this appointment, he was the Principal Scientist and Director of Research Liaison Office in Singapore Institute of Manufacturing Technology (SIMTech), the Additive Manufacturing Programme Manager for the Agency for Science, Technology and Research (A*STAR). Dr Wei's research includes additive manufacturing, flexible and printed electronics. He has authored and co-authored over 800 publications in Chemical Society Reviews, Progress in Materials Science, Science Advances, Advanced Materials, Advanced Functional Materials, ACS Nano, JACS, Energy & Environmental Science, Chemistry of Materials, Journal of Materials Chemistry, Small, Nanoscale, Inorganic Chemistry, Additive Manufacturing, Acta Materialia, Scripta Materialia etc. with citations over 17800 times and H-index of 65. He is holding more than 80 technology disclosures and patents. He is serving several international conference committees and editorial boards.

Pan Wang

Pan Wang is a Research Scientist at A*STAR's Singapore Institute of Manufacturing Technology (SIMTech). He leads the development of the electron beam melting (EBM) process from fundamental research to industrial applications. His research covers the development of high-performance metallic powders for additive manufacturing; design and optimization of new structures for additive manufacturing, promotion of additive manufacturing technology to the industry by overcoming the shortcomings of current technology, and phase transformation and deformation behavior of metastable alloys. He has published over 65 international journal and conference papers on additive manufacturing processes and materials.