Zr50Cu25Ni7.5Co17.5 high-temperature shape memory alloy with excellent thermal stability and large recovery strain, and the associated microstructural deformation mechanism. (November 2020)

• Record Type: Journal Article
• Authors: Gao, Weihong; Yi, Xiaoyang; Song, Gangbing; Wang, Zhenyou; Meng, Xianglong
• Is Part Of: Materials & design. Volume 196(2020)
• Publication Date: 2020-11
• Subjects: Martensitic phase transformation -- Microstructures -- Twinning -- Shape memory alloy (SMA) -- Transmission electron microscopy (TEM); Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2020.109108
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: In this study, we produced a novel Zr50 Cu25 Ni7.5 Co17.5 high-temperature shape memory alloy with the aim of achieving high thermal stability and a good shape memory effect. Differential scanning calorimetry and the 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 the corresponding deformation mechanism. We found that the Zr50 Cu25 Ni7.5 Co17.5 alloy exhibited excellent thermal stability and achieved the best maximum recovery strain of 6.87% (8% pre-strain) observed to date, making it a promising high temperature shape memory alloy. The TEM results indicated that, during the primary stage of the compression cycle, a small number of the (001) compound twins were de-twinning and numerous contraction twins formed. 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 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 the Zr50 Cu25 Ni7.5 Co17.5 alloy were observed. Graphical abstract: Unlabelled Image Highlights: Zr50 Cu25 Ni7.5 Co17.5 is a novel high-temperature SMA with the aim of achieving good thermal stability and shape memory effect. TEM was employed to investigate the microstructure and clarify the corresponding deformation mechanism. As the stress increased, nanoscale (021) and (111) type-I deformation twins formed, and type-B planar defect expanded.