极端热变形条件下Nd-Fe-B基非晶合金中纳米晶的取向生长和结构调控

Studies on the nanocrystallization of amorphous alloys under extreme conditions are of great significance to developing nanocrystalline materials. This project aims at a key scientific problem faced by nanocomposite magnets that controlling the size, fraction, distribution of the soft magnetic nanocrystals are contradictory to the oriented growth of the hard ones. We will study the crystallization kinetics, oriented growth and microstructure evolution of the NdFeB nanocrystals from the amorphous alloys under extreme-conditioned thermal deformation with a high stress (>600 MPa) and a large strain (>80%). The effects of the deformation parameters on the oriented growth of the NdFeB nanocrystals and the microstructure of the soft magnetic nanocrystals will be studied and the texture formation mechanism of the NdFeB nanocrystals will be clarified. The microstructure evolution of the soft magnetic nanocrystals and its effect on the oriented growth of the NdFeB nanocrystals will be investigated. The relations between deformation parameters, microstructure and magnetic properties of the prepared magnets will be established. On the basis, a high-performance anisotropic bulk nanocomposite magnet with a large size is expected to be prepared. These studies will provide an effective strategy to fabricate nanomaterials and will promote the development of the strong nanostructured permanent magnets.

极端热变形条件下非晶合金的纳米晶化研究对先进纳米晶材料的发展具有重要意义。本项目瞄准纳米复合永磁材料研究中软磁纳米晶的形态(尺寸、含量和分布)控制与永磁纳米晶织构形成相矛盾这个关键科学问题，拟采用强力轧制技术产生高应力(>600 MPa)、大应变(>80%)，研究这种极端热变形条件下含软磁纳米晶的Nd-Fe-B非晶合金的晶化动力学、永磁纳米晶的取向生长和纳米晶结构演变。研究变形工艺参数对永磁纳米晶织构形成和软磁纳米晶形态的调控作用；研究预存软磁纳米晶的形态演变及其对永磁纳米晶取向生长的影响；弄清高应力、大应变条件下永磁纳米晶织构的形成机制；建立“变形工艺参数－微结构－磁性能”之间的关系，在此基础上制备高性能、大尺寸各向异性纳米复合永磁材料。本项研究将对我们探索极端条件下先进纳米晶材料的制备提供基础，推动高性能纳米永磁材料的发展。

稀土永磁材料是国民经济和日常生活不可或缺的关键材料，它在电动汽车、风能发电、航空航天、军事等领域有着非常广泛且十分重要的应用，发展低稀土高性能的纳米晶复合永磁材料是国家的重大需求和永磁材料学科前言。本项目瞄准纳米晶复合永磁材料研究中软磁纳米晶的形态(尺寸、含量和分布)控制与永磁纳米晶织构形成相矛盾这个关键科学问题，选取Nd2Fe14B/a-Fe，SmCo7/FeCo，SmCo3/FeCo等纳米晶永磁材料作为研究对象，以非晶做为前驱物，通过热轧强变形获得永磁纳米晶的织构同时获得细小的永磁纳米晶的晶粒尺寸。本项目详细的研究了这些纳米晶材料制备过程中非晶前驱物的制备条件，弄清了非晶制备工艺对所制备非晶结构、晶化动力学以及晶化过程的影响规律。仔细研究并弄清了这些非晶在高应力（>600 MPa）和大应变(变形量>80%)的强力轧制和高压热压缩强束缚变形条件下永磁纳米晶的择优取向生长，微结构和演变和磁特性，获得了明显的永磁纳米晶的晶体织构，并同时保证了软磁纳米晶具有较好的形态（细小的纳米晶尺寸，且分布均匀），弄清了非晶合金微结构和轧制工艺参数对永磁纳米晶织构生长的调控作用以及永磁纳米晶织构形成的物理机制，获得了迄今为止高软相含量（>20%）条件下磁能积最高的（24 MGOe）Nd2Fe14B/-Fe块体纳米晶永磁材料。详细研究了所制备磁体的常温和高温磁特性，建立了“工艺参数－微结构－磁性”之间的关系，为进一步提高低稀土高性能纳米晶永磁材料的磁能积促进该类材料的应用提供了理论和技术指导。