Transformation and Twinning Pseudoelasticities in Fe3Ga Single Crystals
Transformation and Twinning Pseudoelasticities in Fe3Ga Single Crystals
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Fe3Ga 单晶中的相变和孪生赝弹性
DOI：
10.4028/www.scientific.net/ssp.172-174.31
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Y. Umakoshi
中科院分区：
文献类型：
--
作者：
H. Yasuda;Y. Oda;T. Kishimoto;Y. Umakoshi
在具有D03结构的Fe3Ga单晶中，根据热处理、加载轴和应力感，发生基于位错运动、马氏体相变和孪晶的三种类型的赝弹性。在本文中，我们报告了晶体中的转变和孪生赝弹性的细节，重点关注晶体学和温度依赖性。特别是，讨论了孪生赝弹性的驱动力，重点关注原子排列。在α无序区均质化或固溶化的Fe3Ga单晶中，含有大量堆垛层错的14M结构马氏体在加载过程中产生应力，而在卸载过程中通过逆相变而消失，产生应力应变滞后较小的相变伪弹性。相比之下，有序D03晶体中出现了由2.2T型赝孪晶的孪生和解孪引起的孪晶赝弹性，并伴随着应力-应变曲线中的锯齿状流动。在位错运动困难的低温下，孪生赝弹性对应变恢复的贡献变得显着。值得注意的是，假孪晶的形成可以被视为某种位移相变，因为孪晶的晶体结构由于孪晶剪切而变成了斜方晶系，而没有原子改组。 D03 基体与赝孪晶之间的自由能差异导致了孪晶赝弹性。此外，通过在可能发生原子改组的 300°C 退火，伪孪生转化为完美孪生。由于赝弹性驱动力较低，完美双胞胎甚至在完全卸载后仍然存在。
In Fe3Ga single crystals with the D03 structure, three types of pseudoelasticities based on dislocation motion, martensitic transformation and twinning take place depending on the heat treatment, the loading axis and the stress sense. In this paper, we report the detail of the transformation and twinning pseudoelasticities in the crystals focusing on the crystallography and the temperature dependence. In particular, the driving force for the twinning pseudoelasticity was discussed, focusing on the atomic arrangement. In Fe3Ga single crystals homogenized or solutionized in the α disordered region, the martensites with the 14M structure, containing numerous stacking faults were stress-induced during loading, while they disappeared during unloading by the reverse transformation, resulting in the transformation pseudoelasticity with small stress-strain hysteresis. In contrast, twinning pseudoelasticity caused by twinning and untwinning of 2.2T-type pseudo-twins appeared in the well-ordered D03 crystals, accompanied by a serrated flow in the stress-strain curve. The contribution of the twinning pseudoelasticity to strain recovery became significant at low temperatures at which the dislocation motion was difficult. It should be noted that the formation of the pseudo-twins could be regarded as a certain displacive phase transformation since the crystal structure of the twins became orthorhombic due to the twin shear without atomic shuffling. The free energy difference between the D03 matrix and the pseudo-twins resulted in the twinning pseudoelasticity. Moreover, the pseudo-twins were transformed into the perfect twins by annealing at 300 °C where the atomic shuffling could occur. The perfect twins remained even after complete unloading due to their low driving force for the pseudoelasticity.