"Unexpected Thermal Transport, Thermal Expansion, and Thermal Storage Responses via Reversible Martensitic Transformation"

This event is sponsored by FAMU-FSU Engineering Department of Mechanical and Aerospace Engineering.

Abstract: Reversible martensitic transformation in shape memory alloys (SMAs) leads to wellknown shape memory and superelasticity effects. Recently, we have achieved a number of new and unique functionalities in these materials by engineering chemistry, microstructure, crystallographic texture, level of structural disorder, and their interactions with martensitic transformation. In particular, by tailoring the volume fraction, size, morphology, and degree of B2/L21 ordering through controlled thermo-mechanical processing, we can not only shift transformation temperatures over a hundred degrees but also modulate transformation hysteresis and magnetization change that critically determines functional response. We have shown that certain magnetic SMAs exhibit markedly different transport properties compared to conventional SMAs. The thermal and electrical conductivities undergo abrupt, high contrast changes up to a factor of three during martensitic transformation, far exceeding those observed in any other known metallic alloys. What’s even more intriguing is the ability to precisely control the temperature at which this switch occurs, as well as whether it takes place on heating or cooling, by carefully selecting the alloy system, atomic ordering, and applied external fields.

Dr. Ibrahim Karaman

Chevron Professor and Department Head, Materials Science and Engineering

Texas A&M University

Speaker Bio: Dr. Ibrahim Karaman is the Chevron Professor and Head of the Department of Materials Science and Engineering at Texas A&M University. A leading expert in advanced metallic materials, his research focuses on the processing–microstructure– property relationships in ultrafine-grained metals, shape memory alloys, and multi-principal element alloys. He has authored over 350 peer-reviewed publications and holds eight patents, with two licensed by startups founded by his students. Under his leadership, the MSEN department has become the largest in the U.S., earning him prestigious honors including the NSF CAREER Award, ONR Young Investigator Award, and TMS’s Brimacombe Medal.