Advancing Energy Solutions through Additive Manufacturing
Open Access DepositedThe Process-Microstructure Relationship in Thermoelectric Materials Processed with Laser Powder Bed Fusion
In a time of increased global energy demand, advancing energy solutions requires the development of advanced materials and manufacturing techniques. This work addresses the need for efficient waste heat energy recovery, by investigating the process-microstructure relationship in thermoelectric materials fabricated via laser powder bed fusion (PBF-LB). Thermoelectric materials, such as bismuth telluride (Bi₂Te₃) and silicon germanium (Si50Ge50, Si80Ge20), offer a unique capability to directly convert waste heat into electricity. This study leverages high performance computing and advanced simulation techniques to explore how laser processing parameters influence microstructure formation in these thermoelectric materials. By computationally studying additive manufacturing of thermoelectric device components, this work bridges a critical gap in enabling the freeform fabrication of thermoelectric materials for next-generation energy technologies.Understanding and predicting the microstructure formation in additively manufactured thermoelectric materials is important, since the microstructure directly affects the thermoelectric performance. Addressing this research gap requires a fundamental investigation incorporating heat transfer and materials science. While additive manufacturing offers broad advantages in macro scale, it is the unique characteristics of the laser powder bed fusion process that enable a fundamentally new approach to processing thermoelectric materials. A computational approach is employed to predict and characterize grain structure formation. Finite element modeling and Monte Carlo simulations, implemented via the Stochastic Parallel PARticle Kinetic Simulator (SPPARKS), are used to simulate uni-directional and bi-directional laser scanning strategies. The results indicate that laser power and laser scan speed significantly affect solidification parameters and the resulting microstructure. Compared to well-established metal additive manufacturing, the processing of thermoelectric materials requires lower laser power and scan speeds. Despite Bi2Te3’s lower thermal conductivity compared to metals, the use of reduced laser power and scan speed results in comparable temperature gradients in the build. This suggests that processing regimes predominantly shape the thermal profile during laser powder bed fusion. Bulk scale simulations conducted during a year-round internship at Sandia National Laboratories captured variations of grain size and orientation, revealing a strong dependence of the microstructure on the laser scan strategy chosen. The findings of single melt line and bulk part studies underscore the role of tailored processing parameters in promoting grain boundary formation, which enhances thermoelectric performance. This work computationally investigates the process–microstructure relationship in additively manufactured thermoelectric devices. By leveraging both macro- and micro-scale tuning, these devices can more effectively convert waste heat into electricity. The findings demonstrate that adjusting laser scan strategies and processing parameters allows control over grain structure, providing a pathway to optimize thermoelectric device production for effective waste heat energy recovery and multifunctional applications.
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