Phase-Field Simulation of Fusion Interface Events during Solidification of Dissimilar Welds: Effect of Composition Inhomogeneity

Abstract

We investigate the events near the fusion interfaces of dissimilar welds using a phase-field model developed for single-phase solidification of binary alloys. The parameters used here correspond to the dissimilar welding of a Ni/Cu couple. The events at the Ni and the Cu interface are very different, which illustrate the importance of the phase diagram through the slope of the liquidus curves. In the Ni side, where the liquidus temperature decreases with increasing alloying, solutal melting of the base metal takes place; the resolidification, with continuously increasing solid composition, is very sluggish until the interface encounters a homogeneous melt composition. The growth difficulty of the base metal increases with increasing initial melt composition, which is equivalent to a steeper slope of the liquidus curve. In the Cu side, the initial conditions result in a deeply undercooled melt and contributions from both constrained and unconstrained modes of growth are observed. The simulations bring out the possibility of nucleation of a concentrated solid phase from the melt, and a secondary melting of the substrate due to the associated recalescence event. The results for the Ni and Cu interfaces can be used to understand more complex dissimilar weld interfaces involving multiphase solidification.

Joining of dissimilar metals: Issues and modelling techniques

“…26 An application of this technique to microscale modelling of dissimilar welding show that the growth rate of crystals from the base material is not positive when there are strong compositional gradients ahead of the solid/liquid interface. 27 These results corroborate the thermodynamic arguments to explain the difference in fusion line morphologies in most of the dissimilar metal combinations. 2 It is known that sharp concentration gradients play a role in the nucleation of phases 28 and thus are important in dissimilar welding.…”

“…Phase field modelling is an efficient diffuse interface approach to simulate microstructures taking thermodynamic and kinetic aspects into account 26. An application of this technique to microscale modelling of dissimilar welding show that the growth rate of crystals from the base material is not positive when there are strong compositional gradients ahead of the solid/liquid interface 27. These results corroborate the thermodynamic arguments to explain the difference in fusion line morphologies in most of the dissimilar metal combinations 2.…”

μ2mech: A software package combining microstructure modeling and mechanical property prediction

“…Phase field simulation is the most popular technique used for microstructure modeling [1,2]. In recent years, phase field simulations have been used to simulate complex microstructures evolution during different processes, such as solidification [3][4][5][6], spinodal decomposition [7][8][9], precipitate/grain growth [10][11][12][13][14][15][16], coarsening [17,18], and the effect of an external field [19,20].…”