Hi All. I'm simulating a gamma to alpha transformation in Micress for steel. I tried to estimate the angle at the triple junction(for the newly nucleated ferrite grains) and found that the angles are different for different ferrite grains in the same simulation domain(at a particular timestep). I was wondering what all could be the reasons for this difference. The angle at the triple junction is definitely affected by the surface energy values that are chosen, but these values are remaining constant for a particular simulation. So, what could be the reasons for the above difference(Possible physical reasons and the ones that are captured in Micress)? Does the original angle at the austenite grain boundary triple junction affect this? Thanks.
Deepu
Angle at triple junction
Re: Angle at triple junction
Dear Deepu,
in principle, triple point angles should depend on the interface energies of the three involved interfaces, as described by Young's law. However, this only holds for equilibrated triple junctions. Triple junctions can only be in equilibrium, when the involved phases are in thermodynamic equilibrium, all adjacent grain/phase boundaries are perfectly straight, and all boundaries have the freedom to adjust to the correct angle. All these three conditions are not fulfilled in your simulation, the second one will hold only after extremely long (Ostwald) ripening times, and the third probably never.
Nevertheless, I would expect that the average angles should approach the theoretical values with increasing equilibration time and qualitatively follow Young's law when changing interface energies.
Bernd
in principle, triple point angles should depend on the interface energies of the three involved interfaces, as described by Young's law. However, this only holds for equilibrated triple junctions. Triple junctions can only be in equilibrium, when the involved phases are in thermodynamic equilibrium, all adjacent grain/phase boundaries are perfectly straight, and all boundaries have the freedom to adjust to the correct angle. All these three conditions are not fulfilled in your simulation, the second one will hold only after extremely long (Ostwald) ripening times, and the third probably never.
Nevertheless, I would expect that the average angles should approach the theoretical values with increasing equilibration time and qualitatively follow Young's law when changing interface energies.
Bernd