无Co元素FeNiAlTa基形状记忆合金的超（伪）弹性及其相变机制

Cobalt element is a kind of pricious and strategic metals in our country and it is an irreplaceable metal in military industry and aerospace field. For iron-based shape memory alloys are with the advantages of low cost and good workablility, it happened to us that a huge compressive superelasticity (or pseudoelasticity)in cobalt-free FeNiAlTa polycrystalline shape memory alloy is as large as that in FeNiCoAlTaB (NCATB) with cobalt element, which is much larger than that in triditional TiNi shape memory alloys.Thus, our investigations will focus on the superelastic (psudoelasticitic )alloys' preparation process, mechanical and physical properties and their phase transformations mechanisms by means of changing their compositions and optimization of both their rolling and heat treatment processes in order to obtain the best preparation process with the high behaviors,which corresponds to the microstructures and compositions. Meanwhile, their characterizations of phase transformations and the relationship between martensitic transformations and precipitated phases are analysed. This proposal concerning on the superelasticity (psudoelasticity) of the cobalt-free FeNiAlTa based shape memory alloys will benefit to not only phase transformation theories but also reduction of consumption of precious metals such as cobalt (Co) and promotion of the Fe-based alloys. The research results will be orignal.

钴（Co）金属是我国稀缺的、重要的战略物资，在航空航天及军事工业上有着无可替代的作用。本课题组在对具有优异加工性能和低廉价格的Fe基多晶形状记忆合金的研究中发现：无钴（Co）元素的FeNiAlTa合金有着与含Co的FeNiCoAlTaB（NCATB）合金相媲美的、远超过传统TiNi形状记忆合金的超（伪）弹性（>14%）与高强度，其成分差异对其性能亦有影响。本项目以无Co的FeNiAlTa基多晶合金为研究对象，通过改变成分（Ta、B元素）、热处理及轧制等手段，测试超（伪）弹性及其他力学、物理性能等，研究并优化合金的制备工艺，获得与最佳性能相对应的组织、成分与制备工艺；分析其相变特征及析出相与马氏体相之间的耦合关系。从而获得具有高性能、低廉价格和良好加工性的Fe基超（伪）弹性合金，为合金的应用提供工艺保障及理论基础。本项目不但可以节约战略Co金属元素，而且丰富了析出相变与马氏体相变的内涵。

Fe基形状记忆合金价格相对低廉，且各项性能优异.本项目以无Co的FeNiAl基多晶合金为研究对象，通过改变合金成分（Ta、Nb、B）、热处理及轧制等其他工艺手段，研究并优化合金的制备工艺，获得与最佳性能相对应工艺参数、组织结构与成分；分析其相变特征，从而获取具有良好性能、低廉价格和优异加工性能的Fe基超弹性合金，为合金的实际生产应用提供工艺保障及理论基础。研究结果表明：Fe60.5-xNi28Al11.5Tax (x= 0.5,1,1.5 at.%)合金在Ta含量在1%时分别达到最大值2500MPa和16.1%；对Fe41.5-xNi30Co18Al10.5Nbx（x=0%,1%,2%,3%, at.%）组织性能的研究发现：当Nb含量为2%(at.%)时，合金的最大抗压强度、可恢复形变和硬度均达到相对最大，分别为1818.9 Mpa、14.01 %和535.7 HV。轧制及热处理工艺对合金的组织与性能都有影响。合金中析出相 β 相、γ'相以及基体内的未溶解 σ 相三者的大小、数量和分布共同影响着合金的超弹性能; 其中细小均匀分布的 γ'相和 σ 相增强了基体的强度， 有利于合金超弹性性能的提高，β相分布于晶界处不利于合金的性能。

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