Electronic and magnetic techniques to determine microstructure and phase stability

Abstract

Basic to phase stability in alloys is the electronic structure and interactions in the metallic lattice. Occupation degree of the Brillouin zone with electrons, hence the Fermi energy level position with respect to the band edges can be altered by solute additions thus with proper alloying promote specific phase transitions. Combined measurements of electrical conductivity, Hall and Seebeck (thermopower) effects can provide a vast amount of information at the Fermi level, carrier mobility, dominant scattering mechanism, etc. Magnetic measurements can be used to determine the susceptibility to phase formation, i.e. sigma phase formation in high alloy ferrous metals, and to follow the hydrogen content in structural and hydrogen storage alloys. Combining measurements into a 3D plot of Hall (or Seebeck) coefficient, magnetic susceptibility and electrical conductivity, the phase stability relative to a preferred microstructure zone can be indentified and used with the electromagnetic techniques to monitor and control material processing and predict service behavior.