Stability Of Phase Boundaries Research Articles

Stability of phase boundary between L12-Ni3Al phases: A phase field study

The evolution and stability of phase boundaries (PBs) between L12-Ni3Al phases in Ni75Al11V14 alloy aged at 1050k was studied using the microscopic equation phase-field method (MPFM). Four types of L12 PBs were found through atomic configuration, migration and occupation probability (OP). The evolution of metastable PBs and formation of stable PBs were tracked and explored, the effect of coherent elastic strain energy on the evolution and stability of PBs is also investigated by coupling the micro elastic theory with MPFM. In addition, the formation enthalpy, interface energy and electron distribution function of PBs are calculated by FP method, and the stability of PBs is further quantitatively predicted from the perspective of thermodynamic energy and gaining or losing electrons. FP calculation results are consistent with MPFM prediction, and the essence of the transition and stability of PBs is revealed based on the atomic migration dynamics, interface evolution morphology and thermodynamic energy. This is an effective method to further explore the formation and structure of PBs and design high stability PBs.

The combined effects of shear and buoyancy on phase boundary stability

We study the effects of externally imposed shear and buoyancy driven flows on the stability of a solid–liquid interface. A linear stability analysis of shear and buoyancy-driven flow of a melt over its solid phase shows that buoyancy is the only destabilizing factor and that the regime of shear flow here, by inhibiting vertical motions and hence the upward heat flux, stabilizes the system. It is also shown that all perturbations to the solid–liquid interface decay at a very modest shear flow strength. However, at much larger shear-flow strength, where flow instabilities coupled with buoyancy might enhance vertical motions, a re-entrant instability may arise.

Weak variations of Lipschitz graphs and stability of phase boundaries

In the case of Lipschitz extremals of vectorial variational problems, an important class of strong variations originates from smooth deformations of the corresponding non-smooth graphs. These seemingly singular variations, which can be viewed as combinations of weak inner and outer variations, produce directions of differentiability of the functional and lead to singularity-centered necessary conditions on strong local minima: an equality, arising from stationarity, and an inequality, implying configurational stability of the singularity set. To illustrate the underlying coupling between inner and outer variations, we study in detail the case of smooth surfaces of gradient discontinuity representing, for instance, martensitic phase boundaries in non-linear elasticity.

Stability of phase boundaries on thin silicon layers with glass substrates

Phase-change instabilities have been experimentally observed in the laser melting of thin silicon layers on conductive glass substrates. In this study, the polysilicon layer is bounded on the top by a thin layer of glass. This glass covering prevents the occurrence of thermocapillary flows in the silicon melt. A conductive heat-transfer mathematical model is used to predict temperature fields in both the silicon and the glass. Regions of silicon melt are shown to occur; phase-boundary locations are predicted. The stability of the predicted phase boundaries and temperature fields are studied. This analysis shows that the determining factors for stability are the laser power, the shape of the light intensity distribution, and the laser scanning speed. The effect of these parameters on the stability is evaluated. Results from the stability analysis are compared with some experimental results.

Dynamic Stability of Phase Boundaries in First-Order Phase Transitions

Dynamic Stability of Phase Boundaries in First-Order Phase Transitions