Multiple Memory Shape Memory Alloys

Shape memory and pseudoelastic properties of shape memory alloys (SMAs) are attributed a reversible thermoelastic austenite-martensite phase transformation. These functional properties are closely linked to phase transformation temperatures. The high sensitivity of transformation temperatures to alloy composition and processing history has made the fabrication of application-specific alloys very difficult. Traditional SMA fabrication technologies are performance limiting since monolithic components consist of a single set of phase transformation characteristics. The current presentation describes systematic development of a novel technique developed through laser processing research of NiTi alloys. Specifically, controlled changes to local structure and chemical composition using high power density energy sources are shown to significantly augment local transformation temperatures. This method can be implemented to add additional memories in SMAs. Proof of concept was demonstrated by embedding multiple shape memories into a monolithic NiTi component. This method overcomes historical challenges while enabling the realization and development of innovative SMA applications.