文章信息/Info

Title:

Nonhysteretic superelasticity of shape memory alloys at the nanoscale
   

作者:

 丁向東;  宗洪祥 ; 張禎;  孫軍 ; 任曉兵

西安交通大學(xué)金屬材料強(qiáng)度國家重點(diǎn)實(shí)驗(yàn)室

Author(s):

 DING Xiangdong;  ZONG Hongxiang;  Zhang Zhen;  SUN Jun;  Ren Xiaobin

 State Key Laboratory for Mechanical behavior of Materials Xi’an Jiaotong University

關(guān)鍵詞:

形狀記憶合金; 能量滯后; 超彈性; 馬氏體相變

DOI:

10.7502/j.issn.1674-3962.2016.08.05

文獻(xiàn)標(biāo)志碼:

A

摘要:

形狀記憶合金因具有形狀記憶效應(yīng)和超彈性等奇異的功能特性而受到廣泛關(guān)注。但是，受限于一級馬氏體相變的原理性制約，形狀記憶合金的超彈性行為長期以來存在著能量耗散大的難題，并因此降低了材料的精密控制、疲勞性能和能量轉(zhuǎn)化效率等，成為這類材料在高性能領(lǐng)域使用的瓶頸之一。本文從相變形核的角度綜述了相關(guān)降低形狀記憶合金超彈性能量耗散的工作。指出了通過降低材料相變能壘進(jìn)而降低超彈性能量耗散的兩個(gè)可行方案：（1）弱化自發(fā)晶格畸變量；（2）引入空間不均勻性。現(xiàn)有的分子動力學(xué)模擬發(fā)現(xiàn)納米尺度的形狀記憶合金由于其奇異的核-殼結(jié)構(gòu)而同時(shí)滿足以上兩個(gè)解決方案，從而使得塊體材料中強(qiáng)烈的一級馬氏體相變轉(zhuǎn)變?yōu)榧{米尺度下的連續(xù)相變，導(dǎo)致材料出現(xiàn)奇異的零滯后的超彈性行為。這一理論也得到了近期實(shí)驗(yàn)的支持，從而為設(shè)計(jì)窄滯后的形狀記憶合金提供了新思路與新方法。

Abstract:

 Shape memory alloys (SMAs) exhibit two closely related and unique properties: shape memory effect (SME) and superelasticity (SE). Hysteresis in martensitic transformations (MT) limits the usefulness of SMAs that require high sensitivity, high durability and high energy efficiency. Recent studies based on atomic simulations and experiments of nanosized SMAs have indicated promising solutions to slim the MT hysteresis that is associated with superelasiticity. It is summarized that SMAs at the nanoscale demonstrate a decreasing hysteretic superelasticity with reduced feature size. In particular, it exhibits nonhysteretic superelasticity below the critical size. Atomic level investigations show that the decreasing hysteresis is due to weaker spontaneous lattice distortion and spatial heterogeneity, leading to a more continuous phase transformation from the parent phase to martensite under external stress. The theoretical studies are also supported by the latest nanosized SMAs experiments. These findings suggest potential methods to achieve slim hysteresis in conventional bulk SMAs.