Zr 50CU 25NI 7.5CO 17.5 High-Temperature Shape Memory Alloy with Excellent Thermal Stability and Large Recovery Strain, and the Associated Microstructural Deformation Mechanism
Zr 50CU 25NI 7.5CO 17.5 High-Temperature Shape Memory Alloy with Excellent Thermal Stability and Large Recovery Strain, and the Associated Microstructural Deformation Mechanism
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DOI：
10.2139/ssrn.3559981
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发表时间：
2020-04
期刊：
影响因子：
--
通讯作者：
W. Gao;Xiaoyang Yi;G. Song;Zhenyou Wang;Xianglong Meng
中科院分区：
文献类型：
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作者：
W. Gao;Xiaoyang Yi;G. Song;Zhenyou Wang;Xianglong Meng
高温形状记忆合金正受到越来越多的关注。然而，由于原材料成本较高，以及低成本替代品的热稳定性和形状记忆效果较差，目前它们的使用受到限制。要实现这种材料的商业化，必须在保持低材料成本的同时，同时提高热稳定性和形状记忆效应。本研究以高热稳定性和良好的形状记忆效应为目标，研制了一种新型的高温形状记忆合金--Zr50Cu25Ni7.5Co17.5。用差示扫描量热仪和压缩循环测定了合金的相变温度和形状记忆效应，并用透射电子显微镜研究了合金的微观组织，阐明了相应的变形机制。结果表明，该合金具有良好的热稳定性，最大回复应变为6.87%(预应变为8%)。因此，它具有巨大的潜力。透射电子显微镜结果表明，在形成的众多收缩孪晶中，有少量的(001)脱孪晶在初生期提供了回复应变。随着应力的增加，形成了越来越多的纳米级(021)和(111)I型形变孪晶，B型平面缺陷的位移从3d~(001)扩展到8d~(001)。此外，还观察到了新发现的(111)I型形变孪晶和导致大回复应变的B型平面缺陷的扩展。
High-temperature shape memory alloys are receiving increasing interest. However, their use is currently limited due to the high cost of raw materials, and poor thermal stability and shape memory effect of low-cost alternatives. The thermal stability and shape memory effect must both be improved while maintaining low material cost to achieve the commercialization of such materials. In this study, we produced a novel Zr50Cu25Ni7.5Co17.5 high-temperature shape memory alloy with the aim of achieving high thermal stability and a good shape memory effect. Differential scanning calorimetry and compression cycle were utilized to determine the phase transformation temperature and shape memory effect of the alloy, and transmission electron microscopy (TEM) was employed to investigate the microstructure and clarify corresponding deformation mechanism. We found that the Zr50Cu25Ni7.5Co17.5 alloy exhibited excellent thermal stability and achieved the best maximum recovery strain of 6.87% (8% pre-strain) observed to date. Thus, it has great potential. The TEM results indicated that, of the numerous contraction twins that formed, a small number of detwinning (001) compound twins provided the recovery strain during the primary stage. As the stress increased, increasing numbers of nanoscale (021) and (111) type-I deformation twins formed, and the shift displacement of the type-B planar defect has been expanded from 3d~(001) to 8d~(001). Furthermore, the newly found (111) type-I deformation twin and the extension of the type-B planar defect that contributes to the large recovery strain in Zr50Cu25Ni7.5Co17.5 alloy was observed.