论文标题
添加性生产的NITIHF的高温氧化动力学
High-Temperature Oxidation Kinetics of Additively Manufactured NiTiHf
论文作者
论文摘要
基于NITI的高温形状合金（HTSMA）（例如NITIHF）由于其高强度和工作输出以及增加转化温度（TTS）的能力，因此已在广泛的应用中使用。最近，增材制造技术（AM）已被广泛用于制造复杂的形状内存合金组件，而无需进行任何重大修改或工具，并为量身定制了其最终部分的微观结构和关键特性的制造和制造。 NITI合金特性（例如转化温度）可能会因氧化而显着改变，这可能在制造过程或后处理过程中发生。在这项工作中，评估了由选择性激光熔化（SLM）方法制造的富含NII20HF的氧化行为。热重分析（TGA）用于评估在500、700和900 C的不同温度范围内氧化的动力学行为20小时。氧化后，进行了微观结构和化学组成X射线衍射（XRD），扫描电子显微镜（SEM）和能量分散性X射线光谱（EDS）。研究了常规NITI20HF合金的等温氧化动力学，并将结果与AM样品进行了比较。结果表明，在初始阶段的高速率中，氧化增加了两个阶段的氧化速率。随着氧化时间的增加，氧化速率逐渐下降。 NITIHF合金的氧化行为最初遵守对数率定律，然后进行抛物线率定律。 SEM结果表明形成了多层氧化物量表，包括TIO2，NITIO3和HF氧化物。
NiTi-based high-temperature shape memory alloys (HTSMAs) such as NiTiHf have been utilized in a broad range of applications due to their high strength and work output, as well as, their ability to increase the transformation temperatures (TTs). Recently, additive manufacturing techniques (AM) have been widely used to fabricate complex shape memory alloy components without any major modifications or tooling and has paved the way to tailor the manufacturing and fabrications of microstructure and critical properties of their final parts. NiTi alloys properties such as transformation temperatures can be significantly altered due to oxidation, which can occur during the manufacturing process or post-processing. In this work, the oxidation behavior of Ni-rich NiTi20Hf shape memory alloys, which was fabricated by the selective laser melting (SLM) method, is evaluated. Thermogravimetric analysis (TGA) is used to assess the kinetic behavior of the oxidation at different temperature ranges of 500, 700, and 900 C for 20 hours in the air. After oxidation, to evaluate the microstructure and chemical composition X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) was conducted. The isothermal oxidation kinetics of conventional NiTi20Hf alloys were studied, and the results were compared to AM samples. Results show a two-stage oxidation rate at which oxidation increased with the high rate at the initial stage. As the oxidation time increased, the oxidation rate gradually decreased. The oxidation behavior of NiTiHf alloys initially obeyed logarithmic rate law and then followed by parabolic rate law. SEM results showed the formation of a multi-layered oxide scale, including TiO2, NiTiO3, and Hf oxide.
