Puopolo Rocco, Ruschendorf Sally, Thadayil Ajai S K, Cook Scott, Celikin Mert
Materials Design and Processing Laboratory, School of Mechanical and Materials Engineering, University College Dublin, Ireland.
Boston Scientific, Research and Development, Galway, Ireland.
Heliyon. 2024 Sep 3;10(18):e37390. doi: 10.1016/j.heliyon.2024.e37390. eCollection 2024 Sep 30.
This study investigates the influence of cobalt () alloying addition and heat treatment temperature on the phase transformation behaviour controlling the superelasticity and shape memory effect (SME) of Nickel-Titanium (Ni-Ti) alloys, commonly known as nitinol. The microstructural evolution upon heat treatment conducted at a temperature ranging from 440 to 560 °C was thoroughly analyzed via Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). Increase in heat treatment temperatures from 470 °C up to 530 °C led to the dissolution of particles present in as-received (cold-worked) condition. It was determined that addition into the Ni-Ti alloy system resulted in a change in the nucleation and growth kinetics of Ti-rich precipitates, leading to the formation of larger and fewer particles during processing. Both binary and ternary alloys showed a decrease in austenite finish temperature (A) with increasing heat treatment temperatures, however, the rate of decrease was found to be higher for containing ternary alloys. This is linked with faster structural relaxation when Co is present and evidenced by lattice size variation during heat treatment. It is highlighted that heat treatment methodology needs to be tailored to the specific alloy composition for controlling superelasticity and SME via alloy design.
本研究调查了钴（）合金添加量和热处理温度对控制镍钛（Ni-Ti）合金（俗称镍钛诺）超弹性和形状记忆效应（SME）的相变行为的影响。通过差示扫描量热法（DSC）、X射线衍射（XRD）以及扫描电子显微镜/能谱仪（SEM/EDS），对在440至560°C温度范围内进行热处理时的微观结构演变进行了全面分析。从470°C到530°C，热处理温度的升高导致了原始（冷加工）状态下存在的颗粒溶解。研究确定，向Ni-Ti合金体系中添加会导致富钛析出物的形核和生长动力学发生变化，从而在加工过程中形成更大且数量更少的颗粒。二元合金和三元合金的奥氏体终了温度（A）均随热处理温度的升高而降低，然而，含的三元合金的降低速率更高。这与存在钴时更快的结构弛豫有关，并通过热处理过程中的晶格尺寸变化得到证明。需要强调的是，为了通过合金设计控制超弹性和形状记忆效应，热处理方法需要根据特定的合金成分进行调整。
