A model for prediction of pressure and redistribution of gas-forming elements in multicomponent casting alloys

Abstract

A finite element model for simulating macrosegregation in multicomponent alloys is extended to include the calculation of pressure and redistribution of gas-forming elements during solidification. The model solves the conservation equations of mass, momentum, energy, and alloy components, including gas-forming elements such as hydrogen and nitrogen. The results of transport calculations are contrasted with thermodynamic equilibrium conditions to establish the possible formation of pores, assuming that there is no barrier to nucleation of the pores. By solving the transport of gaseous solutes and comparing their Sievert's pressure with the local pressure, the new model can predict regions of possible formation of intergranular porosity. Simulations were performed for a nickel-base alloy (INCONEL 718) in plate castings with equiaxed structure, and the evolution of microporosity for different initial concentrations of hydrogen and nitrogen was analyzed. The simulations showed that during solidification and cooling, a large fraction of the hydrogen escapes and a smaller fraction of nitrogen escapes from the casting. The initial gas concentration is an important factor in porosity formation, but the pressure drop due to shrinkage flow is not very significant. The resulting gas porosity is rather insensitive to initial nitrogen concentration, but sensitive to the concentration of hydrogen.

Numerical simulation of thermal behavior and multicomponent mass transfer in direct laser deposition of Co-base alloy on steel

“…However, a large number of trial experiments are time-consuming and money-consuming. Numerical simulation has offered an effective tool in prediction the thermal behavior and mass transport in direct laser deposition [11][12][13][14][15][16][17][18][19][20][21][22]. A three-dimensional mathematical model has been established in which the temperature field and flow field is obtained [11].…”

“…The solute transfer and composition profiles evolution for binary system Fe-C during double-track direct metal deposition also have been reported [21]. Although the multicomponent mass transfer model has been built in metal casting and chemical engineering [22,23], such study for direct laser deposition has not been reported in the open peerreviewed literature.…”

Analysis of metallurgical aspects and their role in processing and performance of superalloys: A review

“…Simulation techniques, parametric or/and direct methods are usually apply to shape castings [26][27][28][29][30].…”

Element‐free Galerkin method for thermosolutal convection and macrosegregation

“…When the volume fraction of liquid is one, the equations automatically become the Navier-Stokes and transport equations for an all-liquid region and when the volume fraction is zero, no fluid motion is possible and the system reduces to the energy equation. The model has already been presented in Reference [46], but the main features are repeated here for completeness. The following assumptions are used in the development of governing equations: The governing equations in dimensional form are: Continuity equation:…”