Although Nickel-Titanium Shape Memory Alloys (NiTi SMAs) are used in a variety of applications due to their shape memory and superelasticity properties, their features of high ductility, temperature sensitivity, and strong work hardening render these materials difficult to machine. The viability of a new approach in improving the machinability through temperature control using chilled air system application was investigated. Differential scanning calorimetry was used to characterise material response to thermal loads. Microstructure phase identification was evaluated with X-ray diffraction. Micro-milling tests were performed using chilled air system and benchmarked to dry cutting and the use of minimum quantity lubricant (MQL). To augment lubrication, chilled air was also applied concurrently with MQL. Results indicated that the application of chilled air reduced cutting temperature and minimised burr height, while their simultaneous application with MQL further improved the machinability. Further investigation was conducted to explore the influence of the ploughing mechanism on machining performance and product quality. The results pointed to higher feed per tooth producing better outcomes. This paper puts forward a new hypothesis that the machinability could be improved by inhibiting or locking in phase transformation through temperature control, and optimising chip thickness, one of the principal parameters of size effect.

中文翻译：

---

镍钛形状记忆合金微铣削中的冷空气系统和尺寸效应

尽管镍钛形状记忆合金（NiTi SMAs）由于其形状记忆和超弹性特性而在各种应用中使用，但它们的高延展性，温度敏感性和强的加工硬化性使这些材料难以加工。研究了一种通过使用冷空气系统进行温度控制来改善可加工性的新方法的可行性。差示扫描量热法用于表征材料对热负荷的响应。用X射线衍射评价显微组织的相鉴定。使用冷空气系统进行微铣削测试，并以干切削和使用最小量润滑剂（MQL）为基准。为了增加润滑，MQL还同时使用了冷空气。结果表明，冷空气的使用降低了切削温度，并使毛刺高度最小，而它们与MQL的同时使用进一步提高了可加工性。进行了进一步的研究，以探讨耕作机构对加工性能和产品质量的影响。结果表明较高的每颗牙齿进食量可以产生更好的结果。本文提出了一种新的假设，即通过控制温度来抑制或锁定相变并优化切屑厚度（尺寸效应的主要参数之一），可以改善可加工性。进行了进一步的研究，以探讨耕作机构对加工性能和产品质量的影响。结果表明较高的每颗牙齿进食量可以产生更好的结果。本文提出了一种新的假设，即通过控制温度来抑制或锁定相变并优化切屑厚度（尺寸效应的主要参数之一），可以改善可加工性。进行了进一步的研究，以探讨耕作机构对加工性能和产品质量的影响。结果表明较高的每颗牙齿进食量可以产生更好的结果。本文提出了一种新的假设，即通过控制温度来抑制或锁定相变并优化切屑厚度（尺寸效应的主要参数之一），可以改善可加工性。