Effects of Chilled Air on Machinability of NiTi Shape Memory Alloy

Nickel titanium (NiTi) shape memory alloys show reversible diffusionless transition between phases, resulting in special properties and applications. They are ductile, temperature sensitive and their machinability is a major challenge. A new approach to improve their machinability was investigated through the application of chilled air. The temperature phase transformation of the workpiece was characterised by differential scanning calorimetry and micro-milling cutting tests were then undertaken using chilled air, minimum quantity lubricant and a mixture of both. Results showed that the application of chilled air, homogenised the dendritic structure of the workpiece, lower cutting forces and reduced burr height. Simultaneous use of chilled air and minimum quantity lubricant (MQL) showed significant potential for tool wear, burr size reduction and better surface finish.