Effects of Ultra high-hydrostatic pressures on Crystallogaphy and Thermodynamics of Martensitic Transformations

本文研究了静水压力对非因瓦Ti-51at%Ni形状记忆合金长时效和短时效以及因瓦Fe-29.9at%Ni、缓和态Fe-31.9Ni-9.8Co-4马氏体相变的影响。lTi（at%）和Fe-24。Oat%Pt合金，最后一种合金具有不同的有序度（S 0，S>O，S 0.6，S 0.8），通过在1.5GPa的静水压力下进行电阻率测量和光学显微镜观察。其结果是，它被发现的静水压力的依赖性的转变温度测量的因瓦合金是不好的协议，通过使用Patel-Cohen的方程计算的，虽然它是在良好的协议为非因瓦合金。由此推测，因瓦合金的这种不一致性可能是由于存在与因瓦性质有关的自发体积磁致伸缩的物理性质所致。在此基础上，导出了一个新的含s项的方程 ...更多信息 利用Parel和Cohen方程估算了相变温度与静水压力的关系。为了评价新导出的公式中涉及的未知物理量，分别通过静水压下的磁化强度测量和冷台X射线衍射实验，获得了Fe-Ni和Fe-Pt（S0.6，S0.8）合金马氏体相变的s和体积变化。然后，通过将测得的物理量和已知的物理量，如体积模量和吉布斯化学自由能，到新导出的方程中，计算这些因瓦合金的相变温度的压力依赖性。因此，计算的因瓦合金的依赖性是在所有良好的协议与测量的一个在测量的静水压力范围。结果表明，关于自发体积磁致伸缩效应的推测和导出的公式在定量上是正确的。光学显微镜观察表明，无论形成温度如何，静水压下Fe-Ni合金中形成的马氏体形貌与热马氏体的形貌相同。这一结果与作者以前研究的Fe-Ni-C合金的结果一致。少

We have investigated the effect of hydrostatic pressures on martensitic transformations in non-invar Ti-51at%Ni shape memory alloys aged for a long time and a short time and in invar Fe-29.9at%Ni, assuaged Fe-31.9Ni-9.8Co-4. lTi (at%) and Fe-24. Oat%Pt alloys, the last alloy having different degrees of order (S 0, S>O, S 0.6, S 0.8), by carrying out electrical resistivity measurements under hydrostatic pressures up to 1.5GPa and optical microscopy observation. As a result, it was found that the hydrostatic pressure dependence of transformation temperatures measured for invar alloys was not in good agreement with the one calculated by using a Patel-Cohen's equation, although it was in good agreement for non-invar alloys. It was, then, speculated that the disagreement for the invar alloys might be caused by the existence of spontaneous volume magnetostriction, s, which is one of physical properties related to the invar nature. Then, a new equation including the term due to s has been der … More ived to estimate the hydrostatic pressure dependence of transformation temperature by referring to the Parel and Cohen's equation. In order to evaluate the newly derived equation unknown physical quantities involved in the equation, s and the volume change associated with the martensitic transformations for Fe-Ni and Fe-Pt (S 0.6, S 0.8) alloys, have been obtained by magnetization measurements under a hydrostatic pressure and x-ray diffraction experiments with a cold stage, respectively. The pressure dependence of transformation temperatures for those invar alloys has then been calculated by putting the measured physical quantities and the known ones, such as the bulk modulus and Gibbs chemical free energy, into the newly derived equation. Consequently, the calculated dependence for the invar alloys was in all good agreement with the measured one in the measured hydrostatic pressure range. It was, thus, concluded that the speculation as to the effect of spontaneous volume magnetostriction and the derived equation were quantitatively confirmed to be appropriate, optical microscopy observation showed that morphology of the martensities formed in the Fe-Ni alloy under hydrostatic pressure was the same as that of thermallymartensites irrespective of the formation temperature. This result is consistent with that in Fe-Ni-C alloys previously examined by the present authors. Less