MATERIALS  SEMINAR
Department of Materials Science & Engineering
Tuesday November 13, 2018
2:15 – 3:15 ~ SERF 307
Please join us for refreshments at 2:10

"Mesoscale Modeling of Grain Boundaries: From Alloy Segregation to Additive Manufacturing"

Speaker: Dr. Fadi Abdeljawad
Department of Mechanical Engineering
Clemson University, Clemson, SC

Abstract: In this presentation, we cover the development of mesoscopic models aimed at examining the role of grain boundaries (GBs) in processes ranging from solute segregation in nanocrystalline (NC) alloys to sintering kinetics in direct ink write additive manufacturing. 

We first start by examining GB solute segregation as a route to mitigate grain growth processes in NC materials. With the aid of a diffuse interface model that accounts for bulk and GB thermodynamics, solute-GB interactions, and GB migration, we present quantitative analysis of GB segregation and its impact on the thermal stability of NC alloys. Analytical treatments are presented, which establish regimes with the most reduction in GB energy. We then turn our attention to immiscible NC alloys, where the interplay between GB segregation and bulk precipitation determines the extent of solute partitioning between the grains and GBs, affecting the overall thermal stability of these systems.

The second part of the talk is focused on direct ink write (DIW) additive manufacturing. Through a mesoscale modeling framework, we examine the solid-state sintering stage of DIW, which greatly influences many of the salient microstructural features of the printed object. Simulation results are presented that identify materials parameters leading to enhanced densification rates and highlight the role of particle size distribution (PSD) on the microstructural evolution. It is found that a bi-dispersed PSD enhances pore shrinkage rates, but yields microstructures with pores that are highly eccentric, an effect that could be detrimental to the mechanical properties of the printed material. On the whole, our modeling approach provides future avenues to explore the phase space of DIW process parameters and determine ones that lead to optimal microstructures.