铁磁应变玻璃的磁场诱发纳米应变畴转动机制及其功能效应的研究

Strain glass (frozen state of randomly distributed nano-sized strain domains) is a new research field of shape memory alloy systems. The previous studies of the proposer demonstrate that the nano-sized strain domains of strain glass alloy can rotate to response to temperature and stress, which results in many functional properties. Recently, the proposer found a new form of strain glass-ferromagnetic strain glass, of which the nano-sized strain domains are ferromagnetic. Based on previous investigations, it is proposed that a new mechanism, the magnetic field induced rotation of nano-sized strain domains, exists in ferromagnetic strain glass system, which can lead to the magnetostriction and magnetically controlled damping effect. In order to study such a research ideal, the key features of the magnetic field induced rotation of nano-sized strain domains will be investigated in different ferromagnetic strain glass systems. The key features of its associated magnetostriction and magnetically controlled damping effect will be explored systematically. Moreover, the method for improving the performance of these two effects will be studied. Based on these studies, the physical origin of the magnetic field induced rotation of nano-sized strain domains will also be investigated through theoretical simulation. The present study will greatly extend the research and application field of strain glass. It will also provide new principle and experimental foundation for designing multifunctional magnetic alloys.

应变玻璃(随机分布的纳米应变畴的冻结态)是形状记忆合金领域的新兴研究方向。申请人的前期研究表明，应变玻璃合金的纳米应变畴能在温度或应力的作用下发生转动，并能导致许多功能特性。最近，申请人研究发现了一种新形态的应变玻璃--铁磁应变玻璃，其纳米应变畴具有铁磁性。基于前期探索，本项目提出铁磁应变玻璃中存在磁场诱发纳米应变畴转动，且这一新机制能导致磁致伸缩和磁控阻尼效应。为探索这一研究设想，本项目拟在不同的铁磁应变玻璃体系中，研究磁场诱发纳米应变畴转动的基本特征。此外，还将系统研究这一机制所导致的磁致伸缩和磁控阻尼效应的基本特征，并探索改善这两种效应的有效方法。在此基础上，通过理论模拟探索磁场诱发纳米应变畴转动的物理起源。此研究将极大拓展应变玻璃的研究领域和应用范围，并为设计多功能磁性合金提供新原理和实验依据。

铁磁应变玻璃是新形态的应变玻璃，它是短程有序晶格应变(纳米应变畴)和长程有序磁矩的共存态。目前，有关铁磁应变玻璃功能效应的研究并不多。为此，本项目基于纳米应变畴能够对磁场进行响应的设想，探索了铁磁应变玻璃的功能效应及相关机制，得到了以下结论：..(1) 在Fe-Pd-Cu、Fe-Rh和Ni-Mn-Ga-X(X=Co, Fe, Ti)多个合金系的铁磁应变玻璃样品中观察到磁致伸缩效应。发现Fe-Pd-Cu系合金的应变玻璃化转变可诱发模量软化，并进一步导致了较大的磁致伸缩效应。提出铁磁应变玻璃中产生大磁致伸缩效应的条件为样品须具有较低的模量。通过Landau-Ginzburg理论模拟，发现施加磁场时，磁畴将沿着外磁场取向并带动纳米应变畴的再取向，进而导致铁磁应变玻璃的磁致伸缩效应。..(2) 发现Ni-Mn-Ga-Fe合金体系中，铁磁应变玻璃样品的磁控阻尼效应不明显，而铁磁马氏体样品却能表现出显著的磁控阻尼效应。提出了铁磁马氏体合金中产生磁控阻尼效应的条件为磁应力(磁场施加在孪晶界上的等效应力)必须大于其孪生应力(促使孪晶界发生移动所需的临界应力)。发现Ni-Cu-Mn-Ga合金具有覆盖环境温度的宽温域高阻尼效应，提出产生该现象的条件是合金的马氏体相变温度要远高于室温且合金具有较低的模量。..(3) 发现Ni-Fe-Mn-Ga合金体系中预马氏体可充当马氏体与铁磁应变玻璃之间的过渡相。通过Landau-Ginzburg理论模拟，发现缺陷强度越大，形成应变玻璃态所需的临界缺陷浓度越低。发现Co-Ni-Al与Ni-Cu-Mn-Ga合金可同时具有正常弹热和正常磁热效应，通过提高Ni-Cu-Mn-Ga合金的原子有序度，可增强其弹热与磁热效应。..本项目发表标注基金资助的SCI论文9篇，其中包括Materials and Design 1篇、 Scripta Materialia 1篇、Journal of Alloys and Compounds 4篇、Journal of Materials Science 1 篇、Journal of Applied Physics 1 篇、EPL 1篇。在中文期刊上发表标注基金资助的论文1篇。项目组成员参加学术会议4次并作报告。本项目的研究结果为设计新型磁致伸缩与阻尼材料提供了依据。