  Designing the microstructure of Fe-Ni permalloy by additive manufacturing
(AM) opens new avenues to tailor the materials' magnetic properties. Yet,
AM-produced parts suffer from spatially inhomogeneous thermal-mechanical and
magnetic responses, which are less investigated in terms of process simulation
and modeling schemes. Here we present a powder-resolved multiphysics-multiscale
simulation scheme for describing magnetic hysteresis in materials produced via
AM. The underlying physical processes are explicitly considered, including the
coupled thermal-structural evolution, chemical order-disorder transitions, and
associated thermo-elasto-plastic behaviors. The residual stress is identified
as the key thread in connecting the physical processes and in-process phenomena
across scales. By employing this scheme, we investigate the dependence of the
fusion zone size, the residual stress and plastic strain, and the magnetic
hysteresis of AM-produced Fe21.5Ni78.5 permalloy on beam power and scan speed.
Simulation results also suggest a phenomenological relation between magnetic
coercivity and average residual stress, which can guide the magnetic hysteresis
design of soft magnetic materials by choosing appropriate AM-process
parameters.
