Investigation Of Zr, Co Added On NdFeB/α-Fe Nanocrystalline Materials

Nanocrystalline permanent magnetic materials were greatly attented by investigators in all the world beacause they have unprecedented high theoretic energy product.The main reasion for the great difference of the materials’ properties made in laboratory from theoretic value is the microstructures in the materials can not satisfy the request of ideal structure.Nd2Fe14B/α-Fe type of nanocrystalline permanent magnetic materials were selected as the object for main study in this papers.The magnetic properties and microstructure of the materials were improved by adding Zr and Co,as well as by controlling melt-spun and heat treatment process.The microstructures were analyzed by XRD、SEM and FESEM.The magnetic properties of the materials were measured by VSM.The composition of pure NdFeB without any other additional elements were studied.The alloy with composition of Nd9.2Fe84.8gB6was selected as the basic composition for the next study for it has the best microstructures and magnetic properties.Effects on the microstructures and magnetic properties of the materials were studied by adding Zr and Co on the basic composition of Nd9.2Fe84.8B6.The result shows that the best heat treatment time changes with the composition of alloy at a certain temperature.The material’s amorphous stability with composition for Nd9.2Fe84.8-xZrxB6increases at first and then goes down with Zr content increasing. a-Fe phase can be strongly restrained when the Zr content goes up to0.8at%.Good microstructures and magnetic properties can be gained after700℃x20min heat treating and then the a-Fe phase grain is less than10nm.Too little Zr content can not play a great role to restraining a-Fe phase to grow up,but too more of it can be formed into a new soft phase which can cause a-Fe phase to grow up.Enough Zr can be kept in the material to fine the grains with it added,so the coercivity was improved.The studies on Co addition into the material were kept on the base of above works.The magnetic properties of the material increases with Co content adding and can gain the best value when it goes up to4wt%,and the best magnetic properties of the material can be obtained after treated at700℃for15minutes:Mr=0.68T, Hcj=514.2kA/m,(BH)m=121.8kJ/m3.but goes down when exceeds4wt%beacause Co could enter the hard phase to form a new phase of Nd2Co14B which has lower coercivity to Nd2Fe14B.