New Laser Machining Processes for Shape Memory Alloys

摘要

Due to special material properties, shape memory alloys (SMA) are finding increasing attention in micro system technology. However, only a few processes are available for the machining of miniaturized SMA-components. In this connection, laser material processing offers completely new possibilities.This paper describes the actual status of two projects that are being carried out to qualify new methods to machine SMA components by means of laser radiation.Within one project, the laser material ablation process of miniaturized SMA-components using ultra-short laser pulses (pulse duration: approx. 200 fs) in comparison to conventional laser material ablation is being investigated. Especially for SMA micro-sensors and actuators, it is important to minimize the heat affected zone (HAZ) to maintain the special mechanical properties. Light-microscopic investigations of the grain texture of SMA devices processed with ultra-short laser pulses show that the HAZ can be neglected.Presently, the main goal of the project is to qualify this new processing technique for the micro-structuring of complex SMA micro devices with high precision.Within a second project, investigations are being carried out to realize the induction of the two-way memory effect (TWME) into SMA components using laser radiation. By precisely heating SMA components with laser radiation, local tensions remain near the component surface. In connection with the shape memory effect, these tensions can be used to make the components execute complicated movements. Compared to conventional training methods to induce the TWME, this procedure is faster and easier. Furthermore, higher numbers of thermal cycling are expected because of the low dislocation density in the main part of the component.