Mechanical Properties of Injection-Molded Nd-Fe-B Type Permanent Magnets

Abstract

The goal of this research was to investigate the mechanical properties of injection molded Nylon and PPS-based Nd-Fe-B type magnets. The development of new Nd-Fe-B type magnetic materials and the advancement of near-net shape injection molding processes for magnetic component manufacturing have driven the needs to evaluate the mechanical properties of these newly developed materials. PPS (Polyphenylene-Sulfide) and Nylon (Polyamide) are the two most common binders used for these injection molded rare earth magnets.

Since magnetic materials are usually used at elevated and cryogenic temperatures in the automotive and computer industry, the temperature dependent properties ranging from -40 to 180°C are critical for the design of devices utilizing permanent magnetic materials. To enlarge the use of bonded magnets, it is essential to establish a data-base of mechanical characteristics over the operational temperature range. This will provide valuable information for material designers to tailor the formulation and process parameters to achieve the desired mechanical properties.

This research included a series of mechanical properties testing following appropriate ASTM standards. Tensile and bending strengths were evaluated, since these are considered to be the most fundamental characteristics describing the mechanical behavior of materials. Young's modulus was measured using the dynamic impulse vibration method and compared with that obtained from tensile tests. Scanning Electron Microscopy (SEM) analyses indicated that the debonding on the Nd-Fe-B particle and Nylon interface was the main cause of failure at room and elevated temperatures.