Achieving grain refinement and ultrahigh yield strength in laser aided additive manufacturing of Ti−6Al−4V alloy by trace Ni addition

ABSTRACT

Fabricating fine equiaxed grains without undesirable secondary phases is highly challenging for additively manufactured Ti−6Al−4V alloy. The reference amount of Ni addition, which can achieve grain refinement without secondary phase formation, is 0.9 wt. % based on Thermo-Calc calculation. The Ti−6Al−4V−0.9Ni alloy produced by laser-based directed energy deposition demonstrate refined microstructure and an ultrahigh yield strength (1309 MPa). A modified quantitative model is proposed to analyse the strengthening mechanism, and the results demonstrate that the yield strength increment is mainly ascribed to the refined α phase. This work can contribute to the development of customised titanium alloy using additive manufacturing.

KEYWORDS:

• Nickel
• grain refining
• laser-based directed energy deposition
• titanium alloys
• mechanical properties

Disclosure statement

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

Additional information

Funding

This research was supported by Agency for Science, Technology and Research (A*Star), Republic of Singapore, under the IAF-PP program “Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process” [grant number A1893a0031].

Notes on contributors

Shang Sui

Dr Shang Sui is a Research Scientist in Singapore Institute of Manufacturing Technology. He received his B.S. degree in Materials Forming and Control Engineering in 2013 as an outstanding graduate, his Ph.D. in Materials Processing Engineering in 2019, all from Northwestern Polytechnical University of China. He has been engaged in Laser Additive Manufacturing (LAM) technology for 6 years since 2013 when he was a bachelor student at Northwestern Polytechnical University. His research is focused on the microstructural optimization and mechanical performance enhancement of LAM-built nickel-based superalloy Inconel 718.

Youxiang Chew

Dr Youxiang Chew is a Research Scientist and deputy group manager in Singapore Institute of Manufacturing Technology (SIMTech). He joined SIMTech in 2015 and obtained his PhD in Mechanical Engineering from Nanyang Technological University (Singapore). He has over 8 years of experience in Laser directed energy deposition (LDED) technology, focusing on process, residual stress modelling and integration of machine learning with FEM to optimize laser deposition toolpaths. His other research interest includes the development of high entropy alloy and bulk spatially patterned heterostructured multi-materials parts using LDED.

Fei Weng

Dr Fei Weng is a Research Scientist in Singapore Institute of Manufacturing Technology (SIMTech). He received his PhD degree in Materials Science and Engineering from Shandong University, China. His current research interest is in laser aided additive manufacturing of Ti-6Al-4V alloys, nickel-based alloys, high/medium entropy alloys, and other novel high-performance alloys. The emphasis is on microstructure evolution and property evaluation. Dr. Weng also has experience in repair and surface medication of metal components by laser cladding.

Chaolin Tan

Dr Chaolin Tan is a Research Scientist in Singapore Institute of Manufacturing Technology (SIMTech). He received his PhD degree in Materials Processing Engineering from South China University of Technology in conjunction with University of Birmingham (UK) in 2019. His research experience on laser additive manufacturing (LAM) has been over 7 years, with rich research experiences in LAM of advanced high strength steels since 2013. His research interests include LAM new materials and heterostructured materials.

Zhenglin Du

Dr Zhenglin Du is a scientist in the Agency for Science, Technology and Research (A*STAR). He graduate from Nanyang technological University during 2018 with a Doctor of Philosophy (PhD) in Mechanical Engineering with Honors. He specialises in additive manufacturing, process optimisation and metallurgy.

Guijun Bi

Dr Guijun Bi is a Senior Scientist and Group Manager with the Joining & Machining Group in Singapore Institute of Manufacturing Technology. He also holds the adjunct professorship with the National University of Singapore. Dr Bi received his PhD in laser material processing from Fraunhofer Institute for Laser Technology and RWTH Aachen University, Germany. His research focuses on additive manufacturing for surface modification, repair and 3D printing, development of new materials using additive manufacturing, hybrid technologies combined additive and subtractive manufacturing, process monitoring and control, modelling and simulation of additive manufacturing and joining processes.