Order of magnitude increase in actuation fatigue lifetime through partial austenitic transformation of NiTiHf high-temperature shape memory alloys
Order of magnitude increase in actuation fatigue lifetime through partial austenitic transformation of NiTiHf high-temperature shape memory alloys
复制标题
DOI：
10.1016/j.msea.2023.145717
复制
发表时间：
2023-09
期刊：
影响因子：
--
通讯作者：
A. Demblon;J. Mabe;I. Karaman
中科院分区：
文献类型：
--
作者：
A. Demblon;J. Mabe;I. Karaman
NiTiHf高温形状记忆合金（htsma）具有较高的相变温度、强度和热机械稳定性，在固态驱动领域具有广泛的应用前景。最大限度地提高致动器的疲劳寿命，同时防止致动器在使用过程中的行程恶化，是htsma广泛应用面临的两大挑战。许多研究都集中在优化成分和加工以提高性能；然而，事实证明，这在大规模实施时具有挑战性。更简单的解决方案包括优化驱动环境以提高性能。局部热循环是既延长寿命又稳定驱动应变的最有效方法之一。这种方法更能代表执行器的使用方式，因为很少会重复循环到最大输出。先前的研究表明，在低温NiTi和NiTiCu sma中，部分相变延长了疲劳寿命，但在NiTiHf体系中尚未得到最终证实。目前的工作是对Ni50.3Ti29.7Hf20HTSMA加热有限部分循环与完全循环驱动疲劳的影响进行了广泛的分析。结果证实，在部分加热的富镍NiTiHf样品中，每循环相变较少，驱动疲劳寿命增加了一个数量级。更重要的是，在保持作动功输出基本相同的情况下，控制作动应变水平比降低作动应力水平更能有效地提高疲劳寿命，使疲劳寿命相对提高5 ~ 10倍。提供了导致观察到的增强响应的潜在微观结构演变。
The higher transformation temperatures, strength, and thermomechanical stability of NiTiHf high-temperature shape memory alloys (HTSMAs) are attractive for use in solid-state actuation. Maximizing the actuation fatigue lifetime whilst preventing deterioration of actuation stroke during service are the two main challenges facing the widespread application of HTSMAs. Much research has focused on optimizing composition and processing to enhance performance; however, this has proven challenging to implement on a large scale. Simpler solutions involve optimizing the actuation environment to enhance performance. One of the most effective methods to both extend the lifetime and stabilize actuation strain is through partial thermal cycling. This method is more representative of how actuators are employed, as very rarely are they repeatedly cycled to their maximum output. Previous studies have shown partial transformation extends fatigue lifetime in low-temperature NiTi and NiTiCu SMAs, but it has yet to be conclusively demonstrated in the NiTiHf system. The present work is an extensive analysis of the effects of heating limited partial cycling compared to full cycling actuation fatigue of Ni50.3Ti29.7Hf20HTSMA. The results confirm an order of magnitude increase in actuation fatigue lifetime with less transformation per cycle in partially heated Ni-rich NiTiHf samples. More importantly, keeping the actuation work output almost the same, controlling the actuation strain level is shown to be more effective in increasing the fatigue life than reducing the actuation stress level, yielding 5 to 10 times relative improvement in the fatigue life. The underlying microstructural evolution resulting in the observed enhanced response is provided.