Microstructural characterization of laser micro-welded Nitinol wires

Abstract Laser micro-welding has been considered one of the most promising joining methods of manufacturing Nitinol biomedical devices. However, there is still a lack of understanding about how laser micro-welding influences the microstructure. This work attempts to reveal the phase content within various microstructural zones of laser micro-welded crossed Nitinol wires by transmission electron microscopy (TEM) with the assistance of the focused ion beam (FIB) technique. The base metal is composed of a single austenite phase (B2). The fusion zone exhibits the coexistence of austenite matrix and several intermetallics (T 2 Ni, TiNi 3 and Ti 3 Ni 4 ). The precipitation of R-phase was observed in HAZ with B2 matrix due to thermally induced stresses during welding.

[1]  M. Elahinia,et al.  Manufacturing and processing of NiTi implants: A review , 2012 .

[2]  N. Schell,et al.  Shape memory effect of laser welded NiTi plates , 2015 .

[3]  T. Abinandanan,et al.  Phase formation in Ti/Ni dissimilar welds , 2008 .

[4]  M. Jublot,et al.  Sample preparation by focused ion beam micromachining for transmission electron microscopy imaging in front-view. , 2014, Micron.

[5]  Dazhi Yang,et al.  Rotating–bending fatigue of a laser-welded superelastic NiTi alloy wire , 2006 .

[6]  Haichang Jiang,et al.  Microstructure and mechanical behaviors of electron beam welded NiTi shape memory alloys , 2014 .

[7]  José Luis Ocaña,et al.  Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi , 2016 .

[8]  S. Shabalovskaya,et al.  Surface, corrosion and biocompatibility aspects of Nitinol as an implant material. , 2002, Bio-medical materials and engineering.

[9]  T. Yue,et al.  Effects of Process Parameters upon the Shape Memory and Pseudo-Elastic Behaviors of Laser-Welded NiTi Thin Foil , 2011 .

[10]  F. T. Cheng,et al.  Fatigue behavior of laser-welded NiTi wires in small-strain cyclic bending , 2013 .

[11]  F. J. Gil,et al.  Laser welding of NiTi orthodontic archwires for selective force application , 2008, Journal of materials science. Materials in medicine.

[12]  Xiaojun Yan,et al.  Corrosion resistance of a laser spot-welded joint of NiTi wire in simulated human body fluids. , 2006, Journal of biomedical materials research. Part A.

[13]  P. Ji,et al.  Constitutive model for localized Lüders-like stress-induced martensitic transformation and super-elastic behaviors of laser-welded NiTi wires , 2012 .

[14]  José Luis Ocaña,et al.  Residual stress analysis in laser welded NiTi sheets using synchrotron X-ray diffraction , 2016 .

[15]  D. Stróż,et al.  Two-stage R phase transformation in a cold-rolled and annealed Ti–50.6 at.%Ni alloy , 2005 .

[16]  Dazhi Yang,et al.  Corrosion behavior of a laser-welded NiTi shape memory alloy , 2007 .

[17]  T. Yue,et al.  Susceptibility to stress corrosion cracking of NiTi laser weldment in Hanks’ solution , 2012 .

[18]  A. Pelton,et al.  An overview of nitinol medical applications , 1999 .

[19]  Rosa Maria Mendes Miranda,et al.  Welding and Joining of NiTi Shape Memory Alloys: A Review , 2017 .

[20]  J. Anderegg,et al.  The electrochemical characteristics of native Nitinol surfaces. , 2009, Biomaterials.

[21]  Yung-Fu Hsu,et al.  Effect of CO2 laser welding on the shape-memory and corrosion characteristics of TiNi alloys , 2001 .

[22]  Gunther Eggeler,et al.  Ni4Ti3-precipitation during aging of NiTi shape memory alloys and its influence on martensitic phase transformations , 2002 .

[23]  Y. Zhou,et al.  Microjoining and Nanojoining , 2008 .

[24]  Y. Zhou,et al.  Mechanical and Functional Properties of Laser-Welded Ti-55.8 Wt Pct Ni Nitinol Wires , 2011 .

[25]  Rolf Gotthardt,et al.  Interaction between microstructure and multiple-step transformation in binary NiTi alloys using in-situ transmission electron microscopy observations , 1998 .

[26]  T. Yue,et al.  Effect of post-weld heat-treatment on the oxide film and corrosion behaviour of laser-welded shape memory NiTi wires , 2012 .

[27]  G. Thouas,et al.  Metallic implant biomaterials , 2015 .

[28]  Keisuke Uenishi,et al.  Tensile Strength and Pseudo-elasticity of YAG Laser Spot Melted Ti-Ni Shape Memory Alloy Wires , 2004 .

[29]  N. Schell,et al.  On the Mechanisms for Martensite Formation in YAG Laser Welded Austenitic NiTi , 2016, Shape Memory and Superelasticity.