Development of magnetic field driven microactuators made by ferromagnetic shape memory alloy thin films

含Pd约30at%的Fe-Pd铁磁合金表现出由温度和/或磁场变化引起的fcc-fct马氏体相变。这意味着这种Fe-Pd合金有可能表现出磁场诱导的形状记忆效应。具有磁场诱导形状记忆效应的材料的发展使我们可以制造出比钛镍形状记忆合金更快响应的坚固致动器。当我们考虑将来将Fe-Pd合金用作微驱动器时，必须建立一种薄膜形式的该合金的制备工艺。本工作的主要目的是建立该材料的薄膜制备工艺，目标是利用Si-MEMS技术制备Fe-Pd合金微驱动器。首先，我们确定了利用双源直流磁控溅射技术在精确成分控制下沉积Fe-Pd薄膜的最佳条件。Pd含量为28~32at%的薄膜经90 0℃热处理后得到了面心立方结构的…更多的马氏体相变伴随着形状记忆效应。通过不同恒定载荷下的热循环试验，定量表征了退火膜的形状记忆行为。Pd含量小于30at%的Fe-Pd薄膜在室温以上表现出形状记忆效应。当温度低于-80℃时，表现为不可逆应变。这一行为表明，该合金系统的使用温度是有限制的。尽管FCC-FCT转变温度低于室温，但Pd含量超过30at%的Fe-Pd合金的FCT马氏体相变是稳定的。相变温度随外加应力的增加而升高，符合Clasius-Clapayron关系。结果表明，当施加适当的偏压时，Pd含量大于30at%的Fe-Pd薄膜可以在室温以上使用。我们还成功地制作了由焦耳热量驱动的悬臂式微致动器。这些结果已经在国际期刊上发表。较少

Fe-Pd ferromagnetic alloy containing about 30at% Pd shows fcc-fct martensitic transformation which is induced by change in temperature and/or magnetic field. This means that this Fe-Pd alloy has a possibility to show a magnetic field induced shape memory effect. The development of the material showing magnetic field induced shape memory effect allows us to fabricate a robust actuator with faster response than Ti-Ni shape memory alloy. When we consider Fe-Pd alloy to use as a microactuator in future, a fabrication process of this alloy in thin film form must be established. The primary purpose of this work was to establish the fabrication process of this material in thin film form and the goal was to fabricate the Fe-Pd alloy microactuator using Si-MEMS technique.First of all, we have decided the optimal conditions to deposit Fe-Pd films under precise compositional control using dual source dc magnetron sputtering. The films containing 28〜32at% Pd after annealing at 900℃ showed fcc-fct … More martensitic transformation accompanied by shape memory effect. The shape memory behavior of annealed films was characterized quantitatively using thermal cycling tests under various constant loads. The Fe-Pd films containing less than 30at% Pd showed shape memory effect at above room temperature. However, when the temperature was lower than -80℃, they showed irreversible strain originated from fct-bct transformation. This behavior suggests there is the limitation in temperature for use of this alloy system. The fct martensite of Fe-Pd alloy containing more than 30at% Pd was found to be stable though the fcc-fct transformation temperature is lower than room temperature. The transformation temperature rises with increasing applied stress along with Clasius-Clapayron relationship. It is confirmed that the Fe-Pd films containing more than 30at% Pd can be used at above room temperature when a suitable bias load is applied. We have also succeeded to fabricate the cantilever type microactuator which is actually driven by Joule heat. These results have already reported in international journals. Less