A study of stress effects on solidification microstructures at laser sintering of powders using a phase field approach

In this paper, the stress effects on solidification microstructures during laser sintering of alloy powders are investigated, using a phase field approach. Coupling equations among phase, temperature, concentration and strain/stress are derived based on thermodynamic considerations. Thermal and concentration expansions, transformation dilatation, and strain deformation dependency on phase transformation are included in the formulation. A linear stability analysis of solidification front is carried out, to find dispersion relations and a spectrum of wave numbers of unstable perturbations. It is shown, that, in addition to the thermal and mass transfer processes, the strain field generated during microstructure evolution is another important factor that affects the instability mode. An increase in stress increases the maximally wavelength and amplification rate of the unstable fluctuations.