Modeling of solidification of metal-matrix particulate composites with convection

Abstract

A multiphase model for the alloy solidification of metal-matrix particulate composites with convection is developed. Macroscopic transport equations are written for each phase, with unknown parameters modeled through supplementary relations pertinent to the solidification of a binary alloy matrix containing a stationary solid phase and generally nonstationary spherical particles. The model is applied to various one-and two-dimensional systems containing an Al-7 wt pct Si/SiC composite. One-dimensional sedimentation results in nonclustering and clustering particle systems show good agreement with experiments. One-dimensional composite solidification results illustrate the effect of particle clustering and cooling direction on the final macroscopic particle distribution. Two-dimensional results in various unreinforced and reinforced systems illustrate macroscopic particle segregation and its effect on buoyancy-driven melt convection and species macrosegregation. Results indicate a nearly uniform particle distribution for relatively small particles due to negligible particle settling prior to entrapment. For relatively large particles, significant particle settling prior to entrapment results in large denuded and packed zones in the casting. Fluid flow and macrosegregation during solidification are substantially reduced in the presence of particles, due to the relatively large interfacial drag exerted on the liquid by the stationary mush and particle phases.

Prediction of Solidification Microstructure and Columnar-to-equiaxed Transition of Al–Si Alloy by Two-dimensional Cellular Automaton with “Decentred Square” Growth Algorithm

“…The corresponding values for Al-7mass%Si alloy are almost the same as those adopted by Feller and Beckermann. 16) As shown in Table 1 Table 2. Heat transfer coefficient, h, corresponding to each value of T˙for different C 0 is obtained beforehand through several attempts.…”

Simulation of mushy state solidification in stir casting

“…(2012) observed that distribution of the reinforcement particles is dependent on the solidification rate, and at low solidification rates, the reinforcing particles are clustered. Before the occurrence of complete solidification of Al melt, Al will pass through a semisolid state called mushy state (Feller and Beckermann, 1997). Once the mushy state is reached, the reinforcement particles remain in their positions during solidification (Feller and Beckermann, 1997).…”

“…Before the occurrence of complete solidification of Al melt, Al will pass through a semisolid state called mushy state (Feller and Beckermann, 1997). Once the mushy state is reached, the reinforcement particles remain in their positions during solidification (Feller and Beckermann, 1997). Once inside the mush, macroscopic particle motion is largely prevented by the presence of microscopically complex solid–liquid interfaces called dendrites, which entrap the particles (Feller and Beckermann, 1997).…”

“…Once the mushy state is reached, the reinforcement particles remain in their positions during solidification (Feller and Beckermann, 1997). Once inside the mush, macroscopic particle motion is largely prevented by the presence of microscopically complex solid–liquid interfaces called dendrites, which entrap the particles (Feller and Beckermann, 1997). Hashim (1999) experimentally found that the microstructure of rapidly solidified composites has finer dendrite size, and this permits fewer reinforcement particles to be segregated, giving a more homogeneous particle distribution.…”

Numerical Simulation of Microstructure of Al-Si/SiCp Composites during Stir Casting Process with Particle Pushing Model

“…Rohatgi et al 3) presented a simple one-dimensional model based on solidification experiment and studied the effect of stationary particle on temperature profiles and interface velocities. Beckermann et al 4,5) presented a multiphase model based on the volume-averaged technology and predicted the macroscopic particle distribution and the advancing speed of solidification front. Previous particle distribution simulation at microscopic scale mainly focused on the condition of unidirectional solidification and planar S/L interface, most of which studied the interaction process between sole or several particles and solidification interface.…”