NSF-Europe: U.S. - Germany Research Collaboration: "Bridging Length Scales in Deforming Single and Textured Polycrystals of Structural Magnetic Shape Memory Alloys"

该基金探索了从粉末前体和单晶生长制备织构FeNiCoTi和CoNiAl磁性形状记忆合金(MSMA)多晶的方法。一个主要的目标是表征MSMA的微观结构、物理和磁热机械(MTM)行为，以便更好地理解MSMA中磁、热和机械诱导应变的机制。在进行实验研究的同时，建模工作将考虑外部磁场和纹理。采用高压气体雾化法制备粉末，在磁场作用下沿易磁化轴取向，通过热等通道转角挤压(ECAE)和热等静压进行固结。除了在应力、温度和磁场下进行力学测试外，还计划用原位透射电子显微镜和取向成像显微镜表征显微结构，用量热法和X射线衍射仪进行物理表征。金属粉末的固结和SMA的建模将在德克萨斯农工大学进行，而热机械表征将与帕德伯恩大学合作进行，帕德伯恩大学在这类活动方面拥有丰富的经验。织构MSMA多晶的创新加工有望产生高场致驱动力水平、磁激活所需的微结构形态以及比NiTi.%等传统SMA更高的响应频率。这项研究将有助于培育制造和使用SMA和工程磁性材料的本地文化。这不仅将通过在与德国学生和研究人员合作的环境中教育直接参与该项目的研究生和本科生来实现，还将通过将演示和实验室实验纳入当前的课堂活动来实现。研究人员计划利用这项拟议的研究来帮助开发一门新的研究生级别的活性材料课程。德克萨斯农工大学的其他外展和教育活动将被用来向数学和科学教师以及来自不同背景的当前高中生传播所学到的知识。*该NSF项目由多学科活动办公室、材料研究司(金属研究)和国际办公室(西欧)共同资助，作为NSF和欧洲在材料研究方面的合作活动(NSF 02-135)。该项目是与德国帕德伯恩大学合作开展的。

The grant explores fabrication of textured FeNiCoTi and CoNiAl magnetic shape memory alloy (MSMA) polycrystals from powder precursors and single crystal growth. A major objective is to characterize the microstructural, physical and magneto-thermo-mechanical (MTM) behavior for better understanding of the mechanisms responsible for magnetically, thermally and mechanically induced strains in MSMAs. Along with the experimental studies, modeling effort will take into account the external magnetic field and texturing. The powders will be prepared by high-pressure gas atomization, oriented along the easy magnetization axis by application of a magnetic field and consolidated by warm equal channel angular extrusion (ECAE) and hot isostatic pressing. Along with mechanical testing under stress, temperature as well as magnetic field, microstructural characterization is planned with in-situ transmission electron microscopy and orientation imaging microscopy, and physical characterization with calorimetry and X-Ray diffraction. The consolidation of metallic powders and modeling of SMAs will be performed at Texas A&M University while thermomechanical characterization will be performed in collaboration with the University of Paderborn with extensive experience on such activities on active powders. The innovative processing of the textured MSMA polycrystals are expected to lead to high field-induced actuation force levels, desired microstructural morphology for magnetic activation, and higher response frequencies compared to conventional SMAs such as NiTi.%%%The proposed research will help to foster local culture of fabricating and using SMAs and magnetic materials for engineering. This will come about not only by educating graduate and undergraduate students directly involved in this project in a collaborative environment with German students and researchers but also by building demonstrations and laboratory experiments into current classroom activities. The investigators plan to use the proposed research to aid in the development of a new graduate-level course on active materials. Other outreach and education activities at Texas A&M will be used to disseminate knowledge gained to mathematics and science K-12 instructors and current high school students from diverse backgrounds. ***This NSF project is co-funded by the Office of Multidisciplinary Activities, the Division of Materials Research (Metals Research) and International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with University of Paderborn in Germany.