Constructing function domains in NiTi shape memory alloys by additive manufacturing

ABSTRACT

Additive manufacturing (AM) is an orderly construction process involving track-by-track melt pools, which can modulate three characteristic zones between two adjacent melt pools: the heat-affected zone, transition zone, and cellular grain zone. These three zones constitute a function domain that determines the properties of AM metallic materials. In this study, we constructed a novel ordered function domain by AM of modified Ni_50.6Ti_49.4 shape memory alloy powder, which was produced by adding uniform Ni nanoparticles into atomised Ni_49.6Ti_50.4 powder. Interestingly, the three zones of the function domain had the same B2 austenite matrix but inhomogeneous Ni₄Ti₃ clusters and Ti₂Ni nanoprecipitates, which caused different compressive recovery and residual strains in the three zones. The synergetic effect of the three zones generated a stable recovery strain and small hysteresis area in the AMed Ni_50.6Ti_49.4. Our results provide a novel strategy for modulating the microstructure of NiTi by AM to yield superior properties.

GRAPHICAL ABSTRACT

KEYWORDS:

• NiTi shape memory alloy
• additive manufacturing
• function domain
• microstructure
• functional properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Key-Area Research and Development Program of Guangdong Province [grant number 2020B090923001]; National Natural Science Foundation of China [grant number U19A2085]; Key Basic and Applied Research Program of Guangdong Province [grant number 2019B030302010].

Notes on contributors

H. Z. Lu

H. Z. Lu received his bachelor degree from Wuhan University of Science and Technology at 2016. He is currently working toward his Ph.D. thesis on functional properties of NiTi shape memory alloys fabricated by laser powder bed fusion process at South China University of Technology. His research includes NiTi shape memory alloys, titanium alloys, and Ti-based shape memory alloys.

T. Chen

T. Chen received his bachelor degree in school of mechanical & automotive engineering in 2017 from South China University of Technology. He is currently working toward his Ph.D. thesis on fabricating of titanium composites with high mechanical performance, at National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology. his research includes additive manufacturing and powder sintering of Ti alloys and composites.

L. H. Liu

L. H. Liu received PhD degree in mechanical engineering from Tsinghua University at 2019. Currently, he is a postdoctoral researcher at National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials in South China University of Technology. His research interests mainly include bulk metallic glasses, titanium alloys and high-entropy alloys.

H. Wang

H. Wang received his Ph.D. degree from Georgia Institute of Technology in 2010. He is currently an associate professor in Shenzhen University. His research interests focus on laser and additive manufacturing, amorphous alloys and high entropy alloys, two-dimensional nanomaterials and micro-nano devices.⁣

X. Luo

X. Luo received his bachelor degree in school of mechatronics engineering in 2016 from Nanchang University. He is currently working toward his Ph.D. thesis on microstructure, mechanical properties, corrosion resistance, and biocompatibility of Si alloying biomedical β-type titanium alloy produced by additive manufacturing, at National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology.

C. H. Song

C. H. Song is currently an associate professor and deputy director at the School of Mechanical and Automotive Engineering, South China University of Technology. He has been engaged in LPBF research since 2009 and received his PhD at 2014. He completed the development of the fourth generation LPBF metal 3D printing equipment. At present, his research focuses on multi-field assisted LPBF additive manufacturing and structural performance regulation of metal materials in medical and nuclear power fields.

Z. Wang

Z. Wang is a full professor in the School of Mechanical and Automotive Engineering, South China University of Technology, China. After receiving his Ph.D. at Dresden University of Technology, Germany, in 2014, Dr. Wang had worked in AIMR at Tohoku University, Japan, from 2014 to 2016. His current research interest is focused on aluminum alloys, titanium alloys, and their composites with relatively low density and high mechanical performance produced by powder metallurgy, casting and additive manufacturing techniques.

C. Yang

C. Yang is a professor and director of Metallic Materials Institute of Forming Technology and Equipments (National Engineering Research Center of Near-net-shape Forming for Metallic Materials) at South China University of Technology, China. His research team specializes in metal metallurgical processing, including microstructure-properties interrelation, forming technology (additive manufacturing, powder sintering, and pressure casting, etc.) and engineering applications of various metallic alloys and their components (shape memory alloy, advanced titanium alloy, and lead-free brass alloy, etc.).