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Recent Developments in Shape Memory Alloys

authors:H.J. Maier
categories:Articles
year:2016
publication:ACTUATOR 2016, 15th International Conference on New Actuators, Bremen, Germany, 13–15 June 2016, p. 303-308

Abstract

Shape memory alloys (SMAs) feature unique properties, which make them attractive for various applications. Yet, there are certain drawbacks such as difficult processing or expensive constituents, which hinder their widespread use. A case in point is NiTi-based SMAs, which are widely employed in the biomedical field, but are rarely used outside this niche. Lately, however, the extensive research conducted by various groups has resulted in substantial progress and new effects can now be exploited. This overview will address some of the recent developments in this exciting field. One area of research is Fe-based SMAs, which have attracted a lot of recent attention due to their better workability and lower processing costs as compared to NiTi. On the other hand, ferromagnetic Ni- and Co-based SMAs feature additional functional behavior that may be exploited for new applications. Finally, hightemperature SMAs are of great interest as new alloys have become available that do not rely on substantial amounts of noble elements. It appears that processing issues and microstructural instability are the major roadblocks that need to be overcome in all these alloys. Specifically, data from detailed electron optical characterization combined with mechanical tests revealed that the dominant functional  degradation mechanism can vary substantially in the different SMAs. The ramifications of these findings with respect to applications will be discussed and directions for future research will be pointed out.