Experimental investigation and characterization of NiTinol shape memory alloy during wire electrochemical machining

NiTinol-based microstructures have piqued interest in a variety of industrial applications. Nonetheless, due to material features and characteristics, micromachining of NiTinol shape memory alloy (SMA) offers a significant problem due to a detrimental combination of shape memory effect and super-elasticity. In this paper, an investigation into the wire electrochemical machining (WECM) of NiTinol SMA at a low concentration of 0.1 M H2SO4 aqueous acidic electrolyte with effect of small amplitude at low-frequency PZT vibration-assisted axial nozzle jet flushing is presented. During the machining process, initially, the effect of most influencing WECM process parameters i.e. electrolyte flow rate, tool PZT amplitude and frequency, electrolyte temperature during micromachining of NiTinol SMA was studied on machining characteristics for microslit fabrication. Additionally, the effect of pulse voltage, pulse frequency, pulse width and, the wire feed rate was also investigated during machining on micro slit width to understand the benefit of WECM on NiTinol SMA machining in sequential order. Furthermore, after several experiments for controlled machining conditions, finally, NiTinol SMA -based homogeneous minimum slit width of 110 mu m with 0.57 mu m standard deviation were obtained with 120 mu m thick NiTinol sheet at a 100 mu m initial inter-electrode gap. The characteristics of NiTinol SMA were analyzed before and after machining using scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX), X-ray diffraction (XRD) tests. Also, dissolution behavior of NiTinol SMA in 0.1 M H2SO4 aqueous acidic electrolyte was studied. The surface roughness Ra was observed as 0.108 mu m on the machined surface confirming a uniform dissolution during WECM.