Control of martensite variants by magnetic field and giant magnetic field-induced strain in Fe-Pd ferromagnetic shape memory alloys

Fe-Pd 铁磁形状记忆合金中磁场和巨磁场诱导应变对马氏体变体的控制

基本信息

批准号：
15560608
负责人：
FUKUDA Takashi
金额：
$ 2.37万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

Recently, ferromagnetic shape memory alloys have attracted considerable attention because some of them show a giant magnetic field-induced strain of several percent in association with rearrangement of martensite variants. Until now, we have reported that Fe-31.2(at%)Pd alloy exhibits a giant strain of about 3% by the application of magnetic field. Since the giant field-induced strain can be obtained only in the FCT martensite state, it is very important to raise the martensitic transformation temperature. In this study, we first investigated the effect of third elements on the FCT martensitic transformation temperature. As a result, we found that when the FCT transformation temperature is increased, the BCT transformation temperature also increases. The BCT martensite is not suitable for the magnetic field-induced strain and the transformation should be avoided for obtaining good properties. Then, we investigated the most suitable composition at which the FCT transformation temperatur … More e is highest in the Fe-Pd binary system. As a result we found that when Pd content is lower than 30at%, BCT martensite appear in addition to FCT martensite, and the single FCT phase condition is obtained for alloys with Pd content of 30at% and more. We tried to grow a single crystal of Fe-30at% Pd alloy, and found that the composition of specimen varies largely because of a large difference between solidus and liquidus lines at this composition. In order to reduce the segregation introduced during the growing process, we kept the specimen at a temperature just below the melting point for several days, and we succeeded to obtain a homogeneous single crystal whose FCT transformation temperature is close to the room temperature. By using this single crystal, we confirmed that the rearrangement of martensite variants occurs by the application of magnetic field. Furthermore, we measured magnetocrystalline anisotropy constant and twinning stress of an Fe-31.2Pd alloy in a wide temperature range. Using these results, we explained the mechanism of magnetic field-induced strain in ferromagnetic shape memory alloys. Less

最近，铁磁形状的记忆合金吸引了考虑注意力，因为其中一些显示出巨大的磁场诱导的菌株，该应变与马氏体变体的重排相关。到目前为止，我们已经报道了FE-31.2（AT％）PD合金通过应用磁场表现出约3％的巨大应变。由于仅在FCT马氏体状态下才能获得巨大的场诱导的应变，因此提高马氏体转化温度非常重要。在这项研究中，我们首先研究了第三个元素对FCT马氏体转化温度的影响。结果，我们发现，当FCT转换温度升高时，BCT转换温度也会增加。 BCT Martensite不适合磁场诱导的应变，应避免转化以获得良好的特性。然后，我们研究了FCT转化温度的最合适组成，在Fe-PD二进制系统中，更高的E是最高的。结果，我们发现，当PD含量低于30AT％时，BCT Martensite除了FCT Martensite外还出现，并且可为PD含量为30AT％及以上的合金获得单个FCT相条件。我们试图种植Fe-30at％PD合金的单个晶体，发现样品的组成在很大程度上变化了，因为该组成处的固相物和液体线之间存在很大的差异。为了减少在生长过程中引入的隔离，我们将样品保持在熔点以下的温度几天，我们成功获得了均匀的单晶，其FCT转换温度接近室温。通过使用该单晶体，我们确认了Martensite变体的重排是通过应用磁场进行的。此外，我们测量了宽温度范围内Fe-31.2pd合金的磁性各向异性常数和双应力。使用这些结果，我们解释了磁场诱导的铁磁形状记忆合金中磁性应变的机理。较少的