CAREER: Experimental Investigation of Indentation-Induced Two-Way Shape-Memory Surfaces Made From Nickel-Titanium Alloys

技术概述：形状记忆合金能够通过可逆的热弹性马氏体相变进行变形。给定变形处理和/或热处理的规定组合，可以“训练”形状恢复以引起双向形状记忆效应（TWSME）。这种效果的特点是合金对高温和低温形状的记忆，允许两种形状之间的自发变化作为循环温度的函数。本项目旨在研究控制压痕诱导的TWSME表面的微观结构机制。核心假设是，内部应力状态决定了TWSME的优先定向马氏体板的形成，这主要是由(1)压痕过程中产生的位错结构和/或稳定马氏体，(2)合金成分和(3)沉淀的存在决定的。该方法将涉及对初始微观结构的系统操作，然后是已知的多尺度压痕和平面化，以创建TWSME表面。表面形貌和底层微观结构将通过使用先进的显微镜技术进行局部表征来研究。通过PI参与怀俄明大学工程暑期项目（ESP）和EPSCoR本科奖学金项目，高中和大学的学生都将受益于这项拟议的研究。ESP项目邀请高中三年级学生，重点是招收女学生，参加教育实验室，旨在激发对工程的兴趣，提高对怀俄明大学可用研究机会的认识。通过PI参与怀俄明大学工程暑期项目（ESP）和EPSCoR本科奖学金项目，高中和大学的学生都将受益于这项拟议的研究。ESP项目邀请高中三年级学生，重点是招收女学生，参加教育实验室，旨在激发对工程的兴趣，提高对怀俄明大学可用研究机会的认识。非技术概述：形状记忆合金能够通过可逆的热弹性马氏体相变进行变形。给定变形处理和/或热处理的规定组合，可以“训练”形状恢复以引起双向形状记忆效应（TWSME）。这种效果的特点是合金对高温和低温形状的记忆，允许两种形状之间的自发变化作为循环温度的函数。这种材料对执行器和传感器应用具有潜在的兴趣。该项目旨在阐明导致TWSME的材料科学原理，并发展足以产生和控制这种效应的理解。学生培训将涵盖研究生、本科生和高中生。研究生将受益于德国合作者的国际经验。

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. 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.