Shape-memory alloys are capable of undergoing deformation through a reversible thermoelastic martensitic phase transformation. Given a prescribed combination of deformation processing and/or heat treatment, the shape recovery may be "trained" to elicit a two-way shape-memory effect (TWSME). This effect is characterized by the alloy's memorization of both a high and low temperature shape, allowing for spontaneous change between the two shapes as a function of cycling temperature. This project is to investigate the microstructural mechanisms which control indentation-induced TWSME surfaces. The central hypothesis is that the internal stress-state dictates the preferentially directed martensitic plate formation responsible for the TWSME, and this is primarily governed by (1) the dislocation structure and/or stabilized martensite created during indentation, (2) the alloy composition, and (3) the presence of precipitates. The approach will involve systematic manipulation of the initial microstructure, followed by multi-scale indentation and planarization known to create a TWSME surface. Surface topography and underlying microstructure will be investigated through localized characterization using advanced microscopy techniques. Students at both the high school and university levels will benefit from the proposed research through the PI's involvement with the University of Wyoming's Engineering Summer Program (ESP) and EPSCoR Undergraduate Fellowship Program. The ESP program invites high school juniors, with emphasis on recruiting female students, to participate in educational laboratories aimed at generating excitement about engineering and to raise awareness of research opportunities available at the University of Wyoming. Students at both the high school and university levels will benefit from the proposed research through the PI's involvement with the University of Wyoming's Engineering Summer Program (ESP) and EPSCoR Undergraduate Fellowship Program. The ESP program invites high school juniors, with emphasis on recruiting female students, to participate in educational laboratories aimed at generating excitement about engineering and to raise awareness of research opportunities available at the University of Wyoming.
NON-TECHNICAL SUMMARY: Shape-memory alloys are capable of undergoing deformation through a reversible thermoelastic martensitic phase transformation. Given a prescribed combination of deformation processing and/or heat treatment, the shape recovery may be "trained" to elicit a two-way shape-memory effect (TWSME). This effect is characterized by the alloy's memorization of both a high and low temperature shape, allowing for spontaneous change between the two shapes as a function of cycling temperature. Such materials are of potential interest for actuator and sensor applications. This project looks to elucidate the material science principles that lead to TWSME and develop understanding sufficient to produce and control this effect. Student training will span graduate students, undergraduate students and high-school students. Graduate students will benefit from international experience with collaborators in Germany.
