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Recent Developments in Ni-Mn-Ga Foam Research

机译:Ni-Mn-Ga泡沫研究的最新进展

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摘要

Grain boundaries hinder twin boundary motion in magnetic shape-memory alloys and suppress magnetic-field-induced deformation in randomly textured polycrystalline material. The quest for high-quality single crystals and the associated costs are a major barrier for the commercialization of magnetic shape-memory alloys. Adding porosity to polycrystalline magnetic-shape memory alloys presents solutions for (ⅰ) the elimination of grain boundaries via the separation of neighboring grains by pores, and (ⅱ) the reduction of production cost via replacing the directional solidification crystal growth process by conventional casting. Ni-Mn-Ga foams were produced with varying pore architecture and pore fractions. Thermo-magnetic training procedures were applied to improve magnetic-field-induced strain. The cyclic strain was measured in-situ while the sample was heated and cooled through the martensitic transformation. The magnetic field-induced strain amounts to several percent in the martensite phase, decreases continuously during the transformation upon heating, and vanishes in the austenite phase. Upon cooling, cyclic strain appears below the martensite start temperature and reaches a value larger than the initial strain in the martensite phase, thereby confirming a training effect. For Ni-Mn-Ga single crystals, external constraints imposed by gripping the crystal limit lifetime and/or magnetic-field-induced deformation. These constraints are relaxed for foams.
机译:晶界阻碍了磁性形状记忆合金中的孪晶边界运动,并抑制了磁场引起的随机织构多晶材料中的变形。对高质量单晶及其相关成本的追求是磁性形状记忆合金商业化的主要障碍。为多晶磁性形状记忆合金增加孔隙率提供了以下解决方案:(ⅰ)通过孔将相邻晶粒分离来消除晶界,以及(ⅱ)通过用常规铸造替代定向凝固晶体生长工艺来降低生产成本。产生具有变化的孔结构和孔分数的Ni-Mn-Ga泡沫。应用热磁训练程序来改善磁场引起的应变。在通过马氏体相变加热和冷却样品的同时,现场测量循环应变。磁场引起的应变在马氏体相中占百分之几,在加热时的相变过程中连续降低,在奥氏体相中消失。冷却后,循环应变出现在马氏体开始温度以下,并且达到比马氏体相中的初始应变大的值,从而确认训练效果。对于Ni-Mn-Ga单晶,通过限制晶体施加的外部限制会限制寿命和/或磁场引起的变形。这些限制对于泡沫是放松的。

著录项

  • 来源
    《Ferromagnetic shape memory alloys II》|2009年|P.119-124|共6页
  • 会议地点 Bilbao(ES);Bilbao(ES)
  • 作者单位

    Department of Materials Science and Engineering, Boise State University, Boise, ID 83725, USA Harbin Institute of Technology, West Dazhi Street No. 92, 150001, Harbin, P. R. China;

    rnDepartment of Materials Science and Engineering, Northwestern University, Evanston, IL 60208,USA Harbin Institute of Technology, West Dazhi Street No. 92, 150001, Harbin, P. R. China;

    rnDepartment of Materials Science and Engineering, Northwestern University, Evanston, IL 60208,USA Metallurgy and Materials Science Research Institute, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand;

    rnDepartment of Materials Science and Engineering, Boise State University, Boise, ID 83725, USA;

    rnDepartment of Materials Science and Engineering, Boise State University, Boise, ID 83725, USA Helmholtz Center for Materials;

  • 会议组织
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金技术;
  • 关键词

    foam; large strain; polycrystalline; cast structure; fatigue;

    机译:泡沫;大应变多晶铸件结构疲劳;

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