In-situ formation of Ni4Ti3 precipitate and its effect on pseudoelasticity in selective laser melting additive manufactured NiTi-based composites

• Published in: Applied surface science 2018-05, Vol.441, p.862-870
• Main Authors: Gu, Dongdong, Ma, Chenglong
• Format: Article
• Language: English
• Subjects: Ni4Ti3 precipitate; NiTi shape memory alloy; Selective laser melting (SLM)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.01.317

[Display omitted] •The NiTi-based composites was successfully prepared by SLM.•VEDs had a remarkable effect on morphology and content of in-situ precipitated Ni4Ti3.•The formation mechanism of Ni4Ti3 was elucidated.•The pseudoelastic recovery behavior of the matrix was assessed. Selective laser melting (SLM) additive manufacturing technology was applied to synthesize NiTi-based composites via using ball-milled Ti, Ni, and TiC mixed powder. By transmission electron microscope (TEM) characterization, it indicated that the B2 (NiTi) matrix was obtained during SLM processing. In spite of more Ti content (the Ti/Ni ratio >1), a mass of Ni-rich intermetallic compounds containing Ni4Ti3 with nanostructure features and eutectic Ni3Ti around in-situ Ti6C3.75 dendrites were precipitated. Influence of the applied laser volume energy density (VED) on the morphology and content of Ni4Ti3 precipitate was investigated. Besides, nanoindentation test of the matrix was performed in order to assess pseudoelastic recovery behavior of SLM processed NiTi-based composites. At a relatively high VED of 533 J/mm3, the maximum pseudoelastic recovery was obtained due to the lowest content of Ni4Ti3 precipitates. Furthermore, the precipitation mechanism of in-situ Ni4Ti3 was present based on the redistribution of titanium element and thermodynamics analysis, and then the relationship of Ni4Ti3 precipitate, VED and pseudoelastic recovery behavior was also revealed.