Correlation between microstructure, magnetic properties and mechanical behavior of the Permimphy alloy after high-pressure torsion.

Abstract

This study investigates the correlation between coercivity (Hc), grain size (d), and dislocation density in the Permimphy alloy (Fe-80%Ni-6%Mo). The samples used in this study were subjected to varying levels of applied strain through processing by high-pressure torsion (HPT). The microstructure and the magnetic coercivity were analyzed using a scanning electron microscope (SEM), Electron Backscatter Diffraction (EBSD) and Vibrating Sample Magnetometry (VSM). The grain size of the samples varied from 30 μm to 190 nm. This study demonstrated a strong correlation between Hc and microhardness when d > 3 μm. The results show that the coercivity of the Permimphy alloy follows an inverse V-shape with respect to grain size. The coercivity of the samples decreased despite increasing the dislocation density and the hardness when d < 3 μm. This phenomenon is attributed to the ferromagnetic exchange interaction across multiple grains and leads to the alignment of magnetic moments.