Twinning-Induced Elasticity in NiTi Shape Memory Alloys
Twinning-Induced Elasticity in NiTi Shape Memory Alloys
复制标题
DOI：
10.1007/s40830-016-0064-1
复制
发表时间：
2016-03
影响因子：
2.2
通讯作者：
T. Birk;S. Biswas;J. Frenzel;G. Eggeler
中科院分区：
文献类型：
--
作者：
T. Birk;S. Biswas;J. Frenzel;G. Eggeler
形状记忆合金的赝弹性依赖于加载过程中应力诱发马氏体的形成和卸载过程中的反向转变。PE可产生高达8%的可逆应变，并应用于医疗植入物，柔性眼镜框架，阻尼元件等应用。不幸的是，PE表现出强烈的温度依赖性，因此只能在相对较窄的温度窗口内进行开发。目前的工作重点是一个相关的过程，我们称之为孪生诱导弹性（TIE）。它涉及由位错稳定的马氏体变异体的生长和收缩，这是由适当的冷加工引入的。TIE产生的可逆应变约为3%。TIE效应不受PE的强烈温度依赖性的影响。机械TIE性能的弱温度依赖性使得TIE在温度波动较大的应用中具有吸引力。本文主要研究了ni50ti50形状记忆合金丝的TIE效应。初始材料的塑性预变形程度是铸锭冶金工艺路线的关键参数。它控制着可利用的可恢复应变、表观杨氏模量和机械滞回宽度。采用动态力学分析的方法研究了预变形对钛合金基本组织过程的影响。
Pseudoelasticity (PE) in shape memory alloys relies on the formation of stress-induced martensite during loading and on the reverse transformation during unloading. PE yields reversible strains of up to 8 % and is applied in applications such as medical implants, flexible eye glass frames, damping elements, and others. Unfortunately, PE shows a strong temperature dependence and thus can only be exploited within a relatively narrow temperature window. The present work focuses on a related process, which we refer to as twinning-induced elasticity (TIE). It involves the growth and shrinkage of martensite variants which are stabilized by dislocations, which are introduced by appropriate cold work. TIE yields reversible strains of the order of 3 %. The TIE effect does not suffer from the strong temperature dependence of PE. The weak temperature dependence of mechanical TIE properties makes TIE attractive for applications where temperature fluctuations are large. In the present work, we study the TIE effect focusing on Ni50Ti50shape memory alloy wires. The degree of plastic pre-deformation of the initial material represents a key parameter of the ingot metallurgy processing route. It governs the exploitable recoverable strain, the apparent Young’s modulus, and the widths of the mechanical hysteresis. Dynamic mechanical analysis is used to study the effects of pre-deformation on elementary microstructural processes which govern TIE.