NOTE: End date changed to 9/15/2019 per NSSC information (Ed., 6/17/19)

The proposed research project is to test existing analytical and numerical models for phase coarsening using data in NASA Physical Sciences Informatics System. The primary goals of this project are: (1) We will test the diffusion screening theory of phase coarsening by virtue of the microgravity experiments in NASA Physical Sciences Informatics System; (2) We will test numerical modeling such as phase-field simulation and multiparticle diffusion simulation; (3) Large-scale two-dimensional phase-field simulations will be conducted utilizing the microgravity experiments in NASA Physical Sciences Informatics System; (4) We will carry out a three-way comparison among theory, simulation, and microgravity experiments.

Our work has affected multiple disciplines such as materials science, chemistry, and physics within the field of statistical mechanics modeling for pattern formation and evolution. This simulation method and theory are of significant interest for the physical sciences and technologies community.

Using our multi-particle diffusion simulation code, we have accomplished 3-D multiparticle diffusion simulations for phase coarsening at a volume fraction of 0.15. We compared these simulation results qualitatively with archived data derived from CSLM experiments, and theoretical predictions from our diffusion screening theory.

Using our 2-D phase-field simulation code, we have conducted 2-D phase-field simulations for phase coarsening at volume fractions of 0.15, 0.3, 0.7, 0.8. We compared these simulation results with archived data derived from CSLM experiments. We compared the evolved microstructures from phase-field simulations with those recorded from the CSLM experiments for those volume fractions archived in NASA's PSI system.

In order to check the accuracy of this advanced theory of phase coarsening, we measured values of the scaled maximum particle sizes by average size, Rmax. For volume fraction of 0.15, our simulation and diffusion screening theory, and CSLM experiment predicted that Rmax=1.63, 1.68, 1.58, respectively. For volume of 0.3, simulation and diffusion screening theory predicted that Rmax=1.77, and 1.73, respectively, and CSLM experiment yielded Rmax=1.84. These values are in good agreement given both the uncertainties in the statistical experimental and theoretical estimates.

From our microstructures generated from phase-field simulation, the particle size distribution (PSD) can be calculated. From microgravity experimental microstructures the PSD was calculated by CSLM group. In addition, our diffusion screening theory can predict the PSD for volume fraction of 0.15. We compared the PSDs among simulations, theories, and microgravity experiments at volume fraction of 0.15, which is in a good agreement with that from microgravity experiments, and in a reasonable agreement with the prediction of the diffusion screening theory.

NOTE: End date changed to 9/15/2019 per NSSC information (Ed., 6/17/19)

The proposed research project is to test existing analytical and numerical models for phase coarsening using data in NASA Physical Sciences Informatics System. The primary goals of this project are: (1) We will test the diffusion screening theory of phase coarsening by virtue of the microgravity experiments in NASA Physical Sciences Informatics System; (2) We will test numerical modeling such as phase-field simulation; (3) Large-scale three-dimensional phase-field simulations will be conducted utilizing the microgravity experiments in NASA Physical Sciences Informatics System; (4) We will carry out a three-way comparison among theory, simulation, and microgravity experiments; (5) After the testing, an improved theory and a more accurate numerical modeling may be developed if needed.

Our work has affected multiple disciplines such as materials science, chemistry, physics, and nanotechnology within the field of statistical mechanics modeling for pattern formation. This simulation is of significant interest for the physical sciences and technologies community.

Specific research activities include: (1) use data archived in NASA's PSI system from the Coarsening in Solid-Liquid Mixtures (CSLM) microgravity experiments, from which we determine mean and maximum particle sizes in each sample processed through the CSLM microgravity experiments; (2) apply a two-dimensional (2-D) phase-field simulation code, to allow simulation and evolution of initial microstructures that were observed in the CSLM experiments for Sn-Pb solid-liquid phase mixtures, and which provide input data for our phase-field code to numerically evolve coarsened microstructures over time; (3) calculate particle size distributions (PSDs) from the prior NASA CSLM experiments, our phase-field and multiparticle diffusion simulations, and from diffusion screening theory; (4) determine the coarsening rate constant for these binary alloys by tracking their microstructure evolution as initially recorded from the CSLM experiments in NASA's PSI system, and from subsequent phase-field simulations.

We successfully developed a 2-D phase-field computer code, and with it conducted 2-D phase-field simulations for phase coarsening at volume fractions of 0.7 and 0.3. We compared these simulation results with archived data derived originally from NASA’s CSLM experiments.

In addition, we extracted solute concentration distributions from the initial microstructures measured at the earliest processing time as archived from the CSLM experiments for alloys at volume fractions of 0.7 and 0.3. To allow quantitative comparison of our phase coarsening simulations with archived experimental data from CSLM, NASA data were used as inputs for our phase-field simulations, which allowed simulated evolution of coarsened microstructures for the Sn-Pb alloy mixtures processed aboard the International Space Station (ISS).

By contrast, we show that coarsened microstructures from the CSLM experiments and the computed microstructure generated with our phase-field simulation at 24 hours and at 30,000 simulation steps, at volume fraction of 0.3, respectively. We also show that microstructures from the CSLM experiments and the microstructure we computed from our phase-field simulation at 24 hours and at 30,000 simulation steps, at volume fractions of 0.7, respectively.

We compared maximum particle sizes from the CSLM experiments and simulations with theoretical predictions from our diffusion screening theory. In order to check the accuracy of this advanced theory of phase coarsening, we measured values of the scaled maximum particle sizes, (ρ max=Rmax/), where Rmax is the largest radius observed in the coarsened population, and is the average particle radius measured for that population. For example, for the volume fraction of 0.3, simulation and diffusion screening theory predicted that ρ max=1.77, and 1.73, respectively, and CSLM experiment yielded ρ max=1.84. These values are in good agreement given both the uncertainties in the statistical experimental and theoretical estimates.

We show the corresponding particle size distributions, PSDs, obtained from microgravity experiments and our phase-field simulations at volume fractions of 0.7 and 0.3, respectively. These comparisons are encouraging.

The proposed research project is to test existing analytical and numerical models for phase coarsening using data in NASA Physical Sciences Informatics System. The primary goals of this project are: (1) We will test the diffusion screening theory of phase coarsening by virtue of the microgravity experiments in NASA Physical Sciences Informatics System; (2) We will test numerical modeling such as phase-field simulation; (3) Large-scale three-dimensional phase-field simulations will be conducted utilizing the microgravity experiments in NASA Physical Sciences Informatics System; (4) We will carry out a three-way comparison among theory, simulation, and microgravity experiments; (5) After the testing, an improved theory and a more accurate numerical modeling may be developed if needed.

Our work has affected multiple disciplines such as materials science, chemistry, physics, and nanotechnology within the field of statistical mechanics modeling for pattern formation. This simulation is of significant interest for the physical sciences and technologies community.

The proposed research project is to test existing analytical and numerical models for phase coarsening using data in NASA Physical Sciences Informatics System. The primary goals of this project are: (1) We will test the diffusion screening theory of phase coarsening by virtue of the microgravity experiments in NASA Physical Sciences Informatics System; (2) We will test numerical modeling such as phase-field simulation; (3) Large-scale three-dimensional phase-field simulations will be conducted utilizing the microgravity experiments in NASA Physical Sciences Informatics System; (4) We will carry out a three-way comparison among theory, simulation, and microgravity experiments; (5) After the testing, an improved theory and a more accurate numerical modeling may be developed if needed.

Our work has affected multiple disciplines such as materials science, chemistry, physics, and nanotechnology within the field of statistical mechanics modeling for pattern formation. This simulation is of significant interest for the physical sciences and technologies community.

We extracted concentration distributions from the initial microstructures measured at the earliest time archived from the CSLM experiments. To conduct quantitative comparison of simulations with archived experimental data from CSLM, NASA data were used as input for our phase-field code, allowing simulated evolution of coarsened microstructures for the Sn-Pb alloy mixtures processed aboard International Space Station (ISS). Finally, we shall compare the evolved microstructures from phase-field simulations with data recorded from the CSLM experiments for those volume fractions archived in NASA's PSI system, in order to test the numerical model critically and assess its reliability and limitations. We also plan to compare values of the mean and maximum particle sizes from the CSLM experiments with theoretical predictions from diffusion screening theory, in order to check the accuracy of this advanced theory of phase coarsening. We plan to compare the PSDs obtained from microgravity-processed alloys with our computational and theoretical predictions. Lastly, we plan to compare these experimentally derived coarsening rate constants with those based on our computational and theoretical predictions.

The proposed research project is to test existing analytical and numerical models for phase coarsening using data in NASA Physical Sciences Informatics System. The primary goals of this project are: (1) We will test the diffusion screening theory of phase coarsening by virtue of the microgravity experiments in NASA Physical Sciences Informatics System; (2) We will test numerical modeling such as phase-field simulation; (3) Large-scale three-dimensional phase-field simulations will be conducted utilizing the microgravity experiments in NASA Physical Sciences Informatics System; (4) We will carry out a three-way comparison among theory, simulation, and microgravity experiments; (5) After the testing, an improved theory and a more accurate numerical modeling may be developed if needed.