Session: 02-01: Shape Memory Alloy Actuators

Paper Number: 111548

111548 - High Temperature Micro-Scale Actuators From Melt-Spun Shape Memory Alloy: Microstructure and Functional Performance 

In previous communications we have shown the design, fabrication and characterization of a micro-scale self-biasing high-temperature shape memory alloy actuator. Now, we update on the development process with a detailed performance analysis of a packaged device.

Micro-actuators were fabricated using melt-spun NiTiHf ribbons that were cut to shape using an athermal laser process. The as-spun material produced an austenite-finish (A_f) temperature of greater than 120C. The micro-actuator produces a stroke length of up to one millimeter with a force of up to one Newton.

The actuator material was characterized using scanning electron microscopy to reveal the melt-spun microstructure. A columnar-to-equiaxed transition was observed with varying melt-spinning parameters. The transition in the as-cast microstructure was shown to affect the recoverable strain as well as the mechanical properties of the material. The inclusion size and density were also analyzed and shown to be extremely low in both regards.

Functional performance of the actuator was measured using mechanical testing. Actuation stabilized after three-hundred cycles. Ongoing durability testing indicates that fatigue performance of the material is excellent compared to drawn-wire material with similar composition. The conversion efficiency in Joule heating to actuator work is presented. Actuation and reset period testing show that ultra fast actuation speeds can be achieved with the high transformation temperature material. Overall, the micro-scale actuator is shown to provide a compact and efficient power output.

High temperature shape memory alloy actuators enable improved performance in harsh environments or applications that demand higher frequency operation. Melt-spun material processing provides a thin section material that further increases frequency while being geometrically ideal for miniature devices.

Presenting Author: Michael Kuntz Smarter Alloys

Presenting Author Biography: Michael is a Materials Engineer who works to bring Smarter Alloys’ technology to devices that improve everyday life. Michael is passionate about enabling a culture of creativity to solve grand challenges with big ideas. Michael is a licensed Professional Engineer. He holds a PhD in Mechanical Engineering from University of Waterloo and a MBA in Innovation and Entrepreneurship from Wilfrid Laurier University.