Materials Science and Engineering - Spring

 

Team Members

Elliot Crosthwaite
Mariah Preston
Ashly Tercero
Rylee Renck
Juan Pablo Galindo

External Sponsors/Mentors

Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART)
Dr. Aaron Stebner - Georgia Institute of Technology

Internal Sponsors/Mentors

Dr. Marcus Young
Dr. Jincheng Du
Dr. Dwight Burford
Andre Montagnoli
Willow Knight
Alejandro Padilla Gonzalez

Abstract

Current cooling systems rely on vapor-compression cycles that use refrigerant gases such as hydrofluorocarbons (HFCs), which have global warming potentials up to 10,000 times greater than CO2. Solid state cooling based on elastocaloric shape memory alloys (SMAs) offer a promising solution with maximization of cooling efficiency and minimization of energy consumption. Cu-based SMAs designed for elastocaloric cooling possess microstructures consisting of large grain sizes and triple junctions resulting in embrittlement, fatigue cracking, and mechanical failure. CuAlNiTi and CuAlZn have been identified as promising base alloys for elastocaloric devices. In this study, we have selected the following two compositions for investigation: (Cu-29Al-4Ni-1Ti)100-xBx (at%) where x=0,1 and Cu-16Al-16Zn (at%). Two strategies for microstructural improvements were explored: cold working and microstructural processing of ( Cu-29Al-4Ni-1Ti)100-xBx to produce ultrafine-grained structure and heat treatments of Cu-16Al-16Zn to create an oligocrystal structure, an ultracoarse-grained structure. Results from both approaches showed improved elastocaloric performance through engineered microstructural pathways.

Acknowledgments

We would like to thank graduate students Antonio Ferreira and Styler Goring from Georgia Institute of Technology for their assistance with characterization. We would also like to thank the rest of the graduate students in Dr. Young's Lab. We also would like to acknowledge Advanced Materials and Manufacturing Processes Institute (AMMPI) for the resources provided.

Team Members

Maria Gonzalez
Darean Isbell
Ella Nicole Viray
Michael Yerrid

External Sponsor/Mentor

Dr. Lauren Garrison (Commonwealth Fusion Systems)

Internal Sponsors/Mentors

Dr. Thomas Scharf
Dr. Sundeep Mukherjee
Dr. Vijay Vasudevan
Dr. Dwight Burford (course instructor)
Cristian Urias
Christian Garcia
Blake Emad

Abstract

The innermost plasma-facing components (PFCs) and outer structural components (SCs) supporting nuclear fusion devices experience vastly different operating conditions. Resulting differences in properties such as the coefficient of thermal expansion (CTE) make PFC-SC joints difficult to process and prone to failure during thermal cycling. Functionally graded alloys (FGAs) are a promising method to address these joining issues by gradually varying selected properties (e.g. CTE) across a volume. In this work, a CTE-graded FGA between W and V (leading PFC and SC candidates respectively) was designed and fabricated through a one-step spark plasma sintering approach. Structure-properties-performance relationships for the designed FGA were examined through electron microscopy, x-ray diffraction, density measurements, and hardness tests. Preliminary results suggest that even heterogeneous interlayers can still improve the integrity of PFC-SC joints.

Acknowledgments

The team is grateful for the continuous support and guidance of our faculty advisors, mentors, and professors.