Simulation Of Microsegregation Research Articles

Correction: Simulation of Microsegregation in Multicomponent Alloys During Solidifi cation

Correction: Simulation of Microsegregation in Multicomponent Alloys During Solidifi cation

Simulation of microsegregation and the solid/liquid interface progression in the concentric solidification technique

A concentric solidification technique was employed to simulate experimentally the segregation of alloying elements during solidification at the centerline of continuously cast steel. Microstructural development of low carbon steel upon solidification has been observed in situ in a laser-scanning confocal microscope. Microscopic analyses following in situ observations, demonstrate that segregation occurring at steel slabs can reasonably be simulated by the use of the concentric solidification technique. The validity of these experimental simulations has been correlated with mathematical analyses using the Thermo-Calc and DICTRA (Diffusion Controlled Transformation) modeling tools. The effect of cooling rate on the sequence of events during solidification of Fe–0.18%C and Fe–4.2 wt%Ni peritectic alloys was studied and compared with the experimental observations.

Microcracking in multipass weld metal of alloy 690 Part 2 – Microcracking mechanism in reheated weld metal

To elucidate the microcracking (ductility dip cracking) mechanism in the multipass weld metal of alloy 690, the hot ductility of the reheated weld metal was evaluated using three different filler metals with varying contents of impurity elements such as P and S. Hot ductility of the weld metal decreased at temperatures over 1400 K, and the weld metal containing a low quantity of impurity elements showed much higher ductility than that containing a high quantity of impurity elements. Local deformability at high temperature of the alloy 690 reheated weld metal was compared with that of Invar alloy. Grain boundary sliding in alloy 690 occurred not in the intermediate temperature range (800–1000 K), where grain boundary sliding was activated in Invar alloy, but at high temperatures just below the melting temperature of alloy 690. The computer simulation of microsegregation suggested that the deterioration of hot ductility is caused by the grain boundary segregation of impurity elements during the multiple thermal cycling. The ductility dip cracking in the reheated weld metal resulted predominantly from the embrittlement of grain boundaries due to the imbalance between intergranular strength and intragranular strength at high temperature.

Simulation of microsegregation and microstructural evolution in directionally solidified superalloys

A two-dimensional model for solidification and secondary phase precipitation in directionally solidified superalloys is presented, which makes use of a shape function approximation for the isothermal cross-section of the primary dendrites. The phase boundary is represented by a diffuse interface on a finite difference grid, as in phasefield methods. Thus, two-dimensional multicomponent diffusion can be calculated for all phases. Via a Fortran interface, the model is coupled to thermodynamic databases assessed using the ‘calculation of phase diagrams’ (Calphad) approach. In this way, for each time step actual data are available for partitioning, dendritic growth, and nucleation of secondary phases. The model is applied to Ni–Al–Cr as a ternary model system and to the commercial superalloy IN706.