Oligocrystalline Shape Memory Alloys
Oligocrystalline Shape Memory Alloys
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DOI：
10.1002/adfm.201103019
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发表时间：
2012-05-23
影响因子：
19
通讯作者：
Schuh, Christopher A.
中科院分区：
文献类型：
--
作者：
Ueland, Stian M.;Chen, Ying;Schuh, Christopher A.
铜基形状记忆合金(SMA)以单晶形式表现出优异的形状记忆性能。然而，当它们是多晶时，它们的形状记忆性能会受到晶界和三结处相变应变不相容引起的脆性断裂的严重影响。寡晶形状记忆合金是一种微观结构设计的形状记忆合金结构，其总表面积超过总晶界面积，甚至完全不存在三重结。这里展示了寡晶结构如何提供一种在不受单晶加工限制的情况下获得类似单晶的形状记忆合金性能的手段。此外，OSMAS的形成通常涉及到样品尺寸的缩小，样品尺寸效应开始显现。比较了近几年来有关奥斯马斯合金马氏体相变尺寸效应的研究结果，并讨论了与相变热演化有关的一种新的热传递机制。还报道了在无辅助双向形状记忆和加载速率的影响方面的新结果。
Copper-based shape memory alloys (SMAs) exhibit excellent shape memory properties in single crystalline form. However, when they are polycrystalline, their shape memory properties are severely compromised by brittle fracture arising from transformation strain incompatibility at grain boundaries and triple junctions. Oligocrystalline shape memory alloys (oSMAs) are microstructurally designed SMA structures in which the total surface area exceeds the total grain boundary area, and triple junctions can even be completely absent. Here it is shown how an oligocrystalline structure provides a means of achieving single crystal-like SMA properties without being limited by constraints of single crystal processing. Additionally, the formation of oSMAs typically involves the reduction of the size scale of specimens, and sample size effects begin to emerge. Recent findings on a size effect on the martensitic transformation in oSMAs are compared and a new regime of heat transfer associated with the transformation heat evolution in these alloys is discussed. New results on unassisted two-way shape memory and the effect of loading rate in oSMAs are also reported.