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Processing and characterization of high-temperature nickel-titanium-hafnium shape memory thin films.

机译：高温镍钛-形状记忆薄膜的加工与表征。

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摘要

Near-equatomic TiNi thin films are of interest as robust actuator materials in microelectromechanical systems (MEMS) due to the high mechanical energy density associated with reversible martensitic transformations. High-temperature (Ti+Hf)Ni shape memory thin films have been of particular interest because their high transformation temperatures allows use at higher temperatures at which binary TiNi films become inoperative, and also because they can improve the operation frequency for actuation. In this thesis, (Ti+Hf)Ni films having different hafnium contents were prepared by magnetron sputtering. Crystalline films exhibiting martensitic transformation were obtained either by depositing the films at elevated temperatures or by conducting a post-deposition anneal of as-sputtered amorphous films. Phase transformations, microstructure, mechanical properties and shape memory properties of films obtained by different procedures were investigated in order to find the best way to produce high-temperature shape memory films.; In films obtained by post-deposition annealing, the heating rates during annealing were found to significantly affect mechanical properties. Conventional vacuum annealing with heating rates ranging from 5°C/min to 40°C/min resulted in brittle films even though the as-deposited amorphous films were ductile, but rapid thermal annealing (RTA) with a heating rate of 6000°C/min resulted in ductile films having improved martensitic transformation characteristics. Embrittlement of the films annealed by conventional annealing occurred at temperatures well below the crystallization temperature. The RTA treated Ni 49.1Ti36.2Hf14.7 films had room-temperature ductility of 5.8%, fully recoverable strain of 1.7%, maximum recoverable strain of 1.9%, and maximum stress for full strain recovery 200 MPa.; In-situ deposited crystalline Ni48.9Ti 36.6Hf14.5 films demonstrated substantially better properties than the RTA treated samples. The transformation temperatures were higher, transformation hysteresis was lower, and most importantly, the mechanical properties and shape-memory properties were significantly improved. In-situ deposited crystalline Ni48.9Ti36.6Hf 14.5 films had room-temperature ductility of 8.3%, fully recoverable strain of 2.8%, maximum recoverable strain of 3.6%, and maximum stress for full strain recovery of 250 MPa. In addition, the transformation temperatures were effectively increased as more Hf was substituted for Ti. These properties of in-situ deposited crystalline Ni-Ti-Hf films put them in a good position for industrial applications where binary TiNi films are not applicable because of their lower transformation temperatures.
机译：由于与可逆马氏体转变相关的高机械能密度，近等原子的TiNi薄膜作为微机电系统（MEMS）中的坚固执行器材料受到关注。高温（Ti + Hf）Ni形状记忆薄膜已引起特别关注，因为它们的高转变温度允许在二元TiNi薄膜失效的更高温度下使用，并且还因为它们可以提高致动的工作频率。本文通过磁控溅射制备了contents含量不同的（Ti + Hf）Ni薄膜。表现出马氏体相变的结晶膜是通过在高温下沉积膜或通过对溅射的非晶膜进行沉积后退火而获得的。为了找到生产高温形状记忆膜的最佳方法，研究了通过不同程序获得的膜的相变，微观结构，力学性能和形状记忆性能。在通过沉积后退火获得的膜中，发现退火期间的加热速率显着影响机械性能。常规真空退火，加热速率范围为5°C / min至40°C / min，即使沉积的非晶膜具有延展性，也会导致薄膜变脆，但是快速热退火（RTA）的加热速率为6000°C / min最小化导致韧性膜具有改进的马氏体转变特性。通过常规退火退火的膜的脆化发生在远低于结晶温度的温度下。经RTA处理的Ni 49.1 Ti 36.2 Hf 14.7 膜的室温延展性为5.8％，完全可恢复应变为1.7％，最大可恢复应变1.9％，最大应力恢复200 MPa。 原位沉积的结晶Ni 48.9 Ti 36.6 Hf 14.5 薄膜比RTA处理的样品具有更好的性能。转变温度较高，转变磁滞较低，最重要的是，机械性能和形状记忆性能得到了显着改善。 原位沉积结晶Ni 48.9 Ti 36.6 Hf 14.5 薄膜的室温延展性为8.3％，完全可恢复应变为2.8％，最大可恢复应变为3.6％，最大应变为250 MPa。另外，当更多的Hf代替Ti时，转变温度得到有效提高。原位沉积的结晶Ni-Ti-Hf薄膜的这些特性使其在工业应用中处于有利位置，在这些应用中，二元TiNi薄膜由于其较低的转变温度而无法使用。

著录项

  • 作者

    Zhang, Jinping.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 206 p.
  • 总页数 206
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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