烧结NdFeB永磁合金的断裂韧性

The Fracture Toughness of Sintered NdFeB Permanent Magnet

摘要:

用Zwick万能实验机测量了烧结NdFeB永磁合金样品的三点弯曲强度、断裂韧性KIC及弹性模量E。在三点弯曲试验中测得塑变功为0，而断裂功与最大消耗功相等，表明烧结NdFeB合金具有极大的缺口敏感性。缺口敏感的脆性材料用单边切口粱法（SENB）测量KIC时要求较高的抛光精度，以消除表面划痕的影响，比较而言，压痕法测量KIC简便迅速。但由于所用NdFeB合金为烧结复相材料，其微观结构的不均匀性使实验数据较为分散。本研究借助Palmqvist裂纹系统半椭圆裂纹模型HV-KIC的计算公式，采用开微缺口的单边缺口粱试样的KIC和压痕硬度及系列压痕裂纹参数，经回归分析确定了该公式中的经验常数，使之能够较为准确地表征烧结NdFeB永磁合金的断裂韧性。

Abstract:

The bending strength and fracture toughness of sintered NdFeB alloy are tested using a Zwick mechanical properties measure machine. The zero plastic energy in bending procedure shows the brittle characteristic of this kind of material. The Single-Edged-Notch-Bend (SENB) test for its fracture toughness also has the burden of polishing sample. So indentation microcracking is implemented as a simple evaluation method for the fracture toughness of sintered NdFeB alloy. In order to make the experiential parameters reliable in the relation of HV-KIC for Palmqvist crack system, HV and series indentation parameters such as P, a, l are measured to do the regression analysis of fracture toughness that is obtained by SENB test on a notched sample.