Physical Properties of Sintered NdFeB Magnet

Sintered NdFeB permanent magnets, as core functional components, are widely used in instruments and equipment such as motors, electroacoustics, magnet suction, and sensors. During service, magnets are subjected to environmental factors such as mechanical forces, thermal changes, and alternating electromagnet fields. If environmental failure occurs, it will severely affect the functionality of the equipment, causing significant losses. Therefore, in addition to magnet performance indicators, we also need to pay attention to the mechanical, thermal, and electrical properties of sintered NdFeB magnets. This will help us better design and use the magnet steel and is also of great significance for improving its stability and reliability in service.

NdFeB Magnet Mechanical Properties

The NdFeB magnet mechanical properties include hardness, compressive strength, flexural strength, tensile strength, impact toughness, and Young's modulus. Sintered NdFeB magnet is a typical brittle material; its magnet steel has high hardness and compressive strength but poor flexural strength, tensile strength, and impact toughness. This leads to the magnet steel being prone to chipping or even cracking during processing, magnetizing, and assembly. In components and equipment, magnet steel usually needs to be fixed using slots or adhesives, with proper shock absorption and cushioning protection in place.

The fracture surface of sintered NdFeB magnet typically shows intergranular fracture. The NdFeB magnet mechanical properties are mainly determined by its complex multiphase structure and are related to the formula components, process parameters, and structural defects (such as pores, large grains, dislocations, etc.). Generally, the lower the total amount of rare earth elements, the poorer the NdFeB magnet mechanical properties. By adding appropriate amounts of low-melting-point metals such as Cu and Ga, the distribution of the grain boundary phase can be improved to enhance the toughness of the magnet steel. Adding high-melting-point metals such as Zr, Nb, and Ti can form precipitation phases at the grain boundaries, refine the grains, and inhibit crack propagation, thus helping to improve strength and toughness. However, excessive addition of high-melting-point metals will cause the hardness of the magnet material to become too high, significantly affecting processing efficiency.

In actual production, it is challenging to balance the magnet and mechanical properties of magnet materials. Due to cost and performance requirements, easy processing and assembly often have to be sacrificed.

NdFeB Magnet Thermal Properties

The main thermal performance indicators of sintered NdFeB magnet steel include thermal conductivity, specific heat capacity, and thermal expansion coefficient. The performance of magnet steel gradually decreases with an increase in temperature, making the temperature rise of permanent magnet motors a key factor in determining whether the motor can run under load for extended periods. Good thermal conductivity and heat dissipation capabilities are essential to avoid overheating and maintain the normal operation of the equipment. Therefore, we hope that the magnet steel has a high thermal conductivity and specific heat capacity, so that heat can be rapidly conducted and dissipated, while inducing a lower temperature rise under the same amount of heat.