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Investigation of high speed cutting performance and phase transformation behavior of NiTi shape memory alloys

2022    Kaya, Eren; Kaya, Irfan

This paper aims to investigate the high-speed machinability and phase transformation behavior of nickel-titanium shape memory alloys considering the process and post-process perspective. The tool wear results showed that PCD tool has great potential over carbide considering the limitation of quick tool wear in the high cutting speed range. Maximum tool life was achieved at the cutting speed of 130 m/min. The results obtained from differential scanning calorimetry indicated that the latent heats and transformation temperatures of nickel-titanium shape memory alloy are highly cutting speed dependent. Decrease of the cutting speed resulted in increased impair on these properties. It was found that the decrease of the cutting speed causes a decrease in the transformation enthalpy. The results revealed that increased transformation hysteresis is highly cutting speed related. Two hundred fifty m/min and 70 m/min cutting speed values resulted in 31.5 and 37.8 degrees C post-machining transformation hysteresis respectively. Compared to the unmachined sample, a minimal change in functional properties was achieved at the cutting speed of 250 m/min. Likewise, the lowest cutting speed (70 m/min) led to maximum subsurface hardening and deeper machining-induced layer according to metallurgical investigations. Residual austenite formation was evident on the subsurface of the machined specimens.