Verification of Magnetoelastic Martensitic Transformation and Dependence of Crystal Orientations on the Transformation

采用脉冲超强磁场（最大强度为31.75MA/m）对Fe-33.04Ni-10.17Co-3.94Ti（mass%）合金多晶进行磁化测量，研究了磁场对合金多晶热弹性相变的影响。在大坂大学的超高磁场实验室进行磁化测量。所得结果总结如下。通过测量作为温度的函数的电阻率和磁化强度，已经确定了转变温度。测得的<M_s>、和<A_s>温度<A_f>分别为127、60和159 K.通过磁化强度测量，获得了奥氏体和马氏体状态下的自发磁化强度随温度的变化。两相的自发磁化强度之差随温度的升高而减小，<M_s>约为0.3 μ_B。3.在以上温度下的磁场诱发马氏体<A_f>在去除磁场后消失。也就是说，磁致弹性马氏体相变首先被证实是实现时，磁场高于临界一个施加在温度以上<A_f>，然后删除。然而，即使在&lt; T &lt;的温度范围内施加这样的磁场<M_s><A_f>，磁弹性马氏体相变也不能完全实现，因为仍有部分马氏体被保留.温度<M_s>漂移<DELTA>T随诱发马氏体的临界磁场的增大而增大，且温度漂移T与临界磁场之间呈小曲率曲线关系.磁场诱导马氏体的数量随磁场强度的增加而增加，与T无关<DELTA>，尽管它们表现为磁弹性。

Magnetic field-induced martensitic transformations in polycrystals of an ausaged Fe-33.04Ni-10.17Co-3.94Ti (mass%) alloy have been studied to clarify the influence of magnetic fields on a thermoelastic transformation by means of magnetization measurement, applying pulsed ultra high magnetic fields (the maximum strength is 31.75 MA/m) to the alloy polycrystals. The magnetization measurement was carried out at the Ultra Hihg Magnetic Field Laboratory of Osaka University. The results obtained are summarized below.1. Transformation temperatures have been determined by measuring the electrical resistivity and magnetization as a function of temperature. The determined <M_s> , <A_s> and <A_f> were 127, 60 and 159 K, respectively.2. Spontaneous magnetizations in the austenitic and martensitic states have been obtained as a function of temperature by the magnetization measurement. Difference between the spontaneous magnetizations of the two phases decreases with increasing temperature, and the difference at <M_s> was about 0.3 <(mu)_B> . 3. The magnetic field-induced martensites at temperatures above <A_f> disappeared after removing the magnetic field. That is, a magnetoelastic martensitic transformation was first verified to be realized when a magnetic field higher than the critical one was applied at temperatures above <A_f> and then removed. However, even if such a magnetic field was applied in a temperature range, <M_s> < T < <A_f> , the magnetoelastic martensitic transformation could not perfectly be realized, because some martensites were retained.4. The shift of <M_s> temperature, <DELTA> T, increases with the critical magnetic field to induce the martensites, and the relation between the shift and the critical field forms a curved line with small curvature.5. The amount of the magnetic field-induced martensites increases with the strength of magnetic field irrespective of <DELTA> T, although they behave magnetoelastically.