Tensile properties and hardness of cast Fe-Pt magnetic alloys

Abstract

Statement of problem There is little information about the mechanical properties of castable magnetic attachments made of iron-platinum (Fe-Pt) alloys after heat treatment. Material and methods Dumbbell-shaped tensile specimens were cast with 5 alloys: 2 types of Fe-Pt alloys for magnets and keepers, pure Ti, Ti-6Al-7Nb, and Co-Cr alloy. The tensile specimens of the Fe-Pt magnets and keepers underwent different heat treatments to obtain the appropriate properties for a magnet and a keeper. Vickers hardness was measured prior to testing. Tensile testing was conducted in a universal testing machine at a crosshead speed of 2 mm/min until failure. Ultimate tensile strength, yield strength, elongation, and modulus of elasticity were recorded. The data were analyzed using 1-way analysis of variance and the Tukey test (α=.05), fractured surfaces were examined using a scanning electron microscope (SEM). Results The highest tensile and yield strengths were found for Ti-6Al-7Nb, followed by Co-Cr, CP Ti, and the Fe-Pt keeper. There was no significant difference in ultimate tensile strength between the CP Ti and the Fe-Pt keeper. The lowest elongation was found for the Fe-Pt magnet (2.8%), whereas the Fe-Pt keeper had the highest elongation (14.0%). The Fe-Pt magnet and keeper had similar modulus of elasticity values. The hardness of the cast Fe-Pt magnets was the highest among the metals tested. SEM micrographs of the Fe-Pt keepers showed a microstructure with ductile dimple fractures, whereas the Fe-Pt magnets were characterized by brittle fractures at the grain boundaries. Conclusions The mechanical properties of the cast Fe-Pt keepers were similar to those of the cast pure Ti. The Fe-Pt magnets were extremely hard and brittle.