Magnetic characterisation of microstructural feature distribution in P9 and T22 steels by major and minor BH loop measurements

This paper investigates the magnetic properties and parameters measured from major/minor loops and used to characterise different microstructural feature distributions in P9 and T22 steel in different heat treatment or service conditions. The present study introduces a non-destructive way of selecting microstructural features of interest and/or excluding those of little relevance by examination of minor loop measurements at a selected range of applied fields and discusses the fundamental mechanism in terms of domain processes. There is remarkable consistency in magnetic behaviours and properties such as initial/incremental permeability values between the measurements by different techniques. This behaviour has been ascribed to the similar underlying domain processes and hence similar selected microstructural features that are affecting the domain processes.