School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran, Tehran 14395-731, Iran.
J Mech Behav Biomed Mater. 2011 Apr;4(3):298-302. doi: 10.1016/j.jmbbm.2010.10.008. Epub 2010 Nov 2.
The shape memory nickel-titanium alloy has been applied in many fields due to its unique thermal and mechanical performance. One of the successful applications of NiTi wires is in orthodontics because of its good characteristics such as low stiffness, high spring back, high stored energy, biocompatibility, superelasticity and shape memory effect. The mechanical properties of wires are paid special attention which results in achieving continuous optimal forces and eventually causing rapid tooth movement without any damage. The behavior of the alloy can be controlled by chemical composition and thermo-mechanical treatment during the manufacturing process. In this study two kinds of commercial superelastic NiTi archwires of 0.41 mm diameter were investigated: Copper NiTi and Highland Metal. The chemical analysis of both wires was estimated by energy dispersive spectroscopy (EDS). It was showed that Copper NiTi wire contained copper and chromium. The two types of wires were exposed to different heat treatment conditions at 400 and 500 °C for 10 and 60 min to compare the behavior of the wires at aged and as-received conditions. Phase transformation temperatures clarified by differential scanning calorimetry (DSC) showed B2 <--> R <--> B19 transformation in Highland Metal wire and B2 <--> B19(') transformation in Copper NiTi wire. Three point bending (TPB) tests in the certain designed fixture were performed at 37 °C to evaluate the mechanical behavior of the wires. The experimental results revealed the superelastic behavior of the Highland Metal wire after 60 min ageing at 400 and 500 °C and the plastic deformation of the Copper NiTi wire after annealing due to the effect of copper in the alloy composition.
形状记忆镍钛合金由于其独特的热机械性能，已在许多领域得到应用。NiTi 丝的一个成功应用是在正畸学中，因为它具有低刚度、高回弹性、高储能、生物相容性、超弹性和形状记忆效应等良好特性。线材的力学性能受到特别关注，这使得能够实现持续的最佳力，最终导致牙齿快速移动而不会造成任何损伤。在制造过程中，通过化学成分和热机械处理可以控制合金的行为。在这项研究中，研究了两种商业超弹性 NiTi 弓丝，直径为 0.41 毫米：铜镍钛和高地金属。通过能谱分析（EDS）对两种线材的化学成分进行了估计。结果表明，铜镍钛丝含有铜和铬。两种类型的线材在 400 和 500°C 下分别暴露于 10 和 60 分钟的不同热处理条件下，以比较线材在时效和原始状态下的行为。差示扫描量热法（DSC）表明的相转变温度表明，高地金属丝发生 B2 <--> R <--> B19 转变，而铜镍钛丝发生 B2 <--> B19(') 转变。在 37°C 下，在特定设计的夹具中进行三点弯曲（TPB）测试，以评估线材的力学性能。实验结果表明，高地金属丝在 400 和 500°C 时效 60 分钟后表现出超弹性行为，而铜镍钛丝在退火后由于合金成分中铜的作用发生塑性变形。
