Plastic relaxation during diffusion-controlled growth of Widmanstätten plates

A phase field model accounting for anisotropic elasticity as well as isotropic strain gradient viscoplasticity is employed to study the diffusion-controlled growth of acicular precipitates. Following some recent work (Cottura et al., 2014), it is shown that an anisotropic eigenstrain can generate microstructures with the morphological and kinetic feature of Widmanstatten plates. Then, we demonstrate that when isotropic viscoplasticity is considered, the plate lengthening remains stationary in isothermal conditions, but features slower growth rates and larger tip radii.