Nd-Fe-B快淬磁粉在真空中热压,继续进行不同变形温度和不同应变率的热模压处理.通过分析不同变形温度下的热变形过程中应力一应变率关系,对热模压Nd-Fe-B磁体的热变形行为进行了研究并由此得到了描述热变形过程的关键参数.为了清楚理解晶粒边界滑移和各向异性晶粒长大在变形过程中所起的作用,利用三维有限元软件(DEFORM-F3)对热变形过程进行模拟,得到Nd-Fe-B柱状磁体在变形过程中不同阶段不同区域的有效应变值模拟结果.模拟结果表明:有效应变随磁体压下率的增加而提高,并在磁体中心区域显示了最大应变值,在轴向和径向两个方向由于模具壁与磁体间的摩擦力而减小.磁性能和XRD测试显示剩磁和晶体取向随压下率的增加而得到改善,剩磁在压下率为75%时接近饱和,在80%压下率处达到峰值.有效应变作为c抽取向的依赖因素,在一定程度上反映了热变形磁体的磁性能.%Melt-spun powders were hot compacted in vacuum and die-upset forged at different deformation temperature with different strain rates. By analyzing the relationship of stress and strain at different deformation temperature during die-upset forging process, deformation behavior of Nd-Fe-B magnets was studied and parameters for describing plastic deformation were obtained. In order to clearly understand the role of deformation process in grain-boundary sliding and anisotropic grain growth simulations of the die-upset process were performed using DEFORM-F3, a three-dimensional finite element method based deformation modeling software.Strains in different regions of a cylindrical Nd-Fe-B magnet at different stages of the die-upset process can be determined. Simulation results reveal that the effective strain increased with the increasing of deformation ratio and show a maximum value at the central region. However effective strain decreases in the both direction of thickness and radius due to friction between die-wall and magnet interface. The uniformity of effective strain improves with the increasing of deformation ratio. The measurements of magnetic properties and XRD show that magnetic performance and crystal alignment improve with the increasing of deformation ratio and indicate a saturation behavior at the deformation ratio of 75％. Simulation result is good agreement with the measurement of magnetic properties and XRD.
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