基于磁相变机制的过渡金属合金磁致应变效应研究

Magnetostrain material is a kind of important magnetic functional material due to its applications in industry and military. Some magnetic phase transition alloys show an abrupt change in lattice constant during the phase transition, which makes them become the promising magnetostrain materials. From the practical application point of view, there are server problems in the study of this field (1) the phase transition temperature is not around the room temperature; (2) the magnetic field to drive the phase transition is high; (3) the degree of orientation of the alloy is not ideal; (4) Some magnetic phase transition alloys are brittle. In this project, we will carry out the investigation of magnetostrain in CoMnSi and CoMnGe alloys. The phase transition temperature can be adjusted by elemental substitution and the critic field for inducing the phase transition can be decreased by increasing the change of magnetization before and after the phase transition. By Annealing alloys under the high-magnetic-field and orientating the mixture of alloy particles and epoxy in magnetic field, the degree of orientation of the alloys can be increased. Based on it, we will carry out the research to optimize the magnetostrain performance of these alloys and hope that this study can provide the theoretical and experimental evidence for exploring the new mechanism of magnetostriction and widening the applications of magnetic phase transition alloys.

磁致应变材料因在工业和军事上的应用而成为一种重要的磁性功能材料。有些磁相变合金在相变时伴随着晶格常数的突变，有望成为一类新型磁致应变材料。从实际应用出发，该领域的研究中还存在着以下问题（1）相变温度不在室温附近；（2）驱动相变所需磁场较大；（3）样品的晶体取向度不高；（4）部分样品的脆性较大。本项目将开展过渡金属磁相变合金CoMnSi和CoMnGe的磁致应变研究。通过元素替换和增加相变前后磁化强度差值等方法来调节相变温度和降低临界磁场。采用强磁场下退火和金属颗粒与树脂混溶后磁场取向的方法来制备高取向度样品。在此基础上开展优化磁相变合金磁致应变性能的研究，为探索新型磁致伸缩机制和拓宽磁相变合金应用领域提供理论和实验证据。

磁致应变材料是一类重要的磁性功能材料，在工业和军事上有着广泛的应用。本项目中，我们基于磁相变合金，利用磁场驱动的磁弹相变或磁结构相变获得了室温下的巨磁致应变效应。主要研究成果包括：（1）利用强磁场凝固的方法获得了有织构且致密度高的MnCoSi基合金，通过Si缺位的方法，降低了相变临界场，调节了三相点，获得了室温下可回复的巨磁致伸缩效应；（2）为了进一步降低驱动相变的磁场，我们通过强磁场凝固的方法制备了Fe取代Mn或Mn缺位的MnCoSi合金，研究结果表明，这些合金的相变驱动临界场大幅降低。对于Mn0.88CoSi合金，在1T的磁场和300K时，其最大磁致伸缩可达1230ppm；（3）在MnCoGe合金中，我们通过Mn缺位的方法将磁结构相变温度调节到室温附近。利用磁场下粘接取向的方法获得了有织构的Mn0.965CoGe合金，在室温附近观察到了大磁致应变效应。这些研究成果为探索新型磁致伸缩机制和拓宽磁相变合金应用领域提供了重要的理论和实验证据。