College of Engineering News • Iowa State University

Two professors and Phd student predict new phase transformation in physics journal

Valery Levitas_Phase Transformation Figure 3Valery Levitas, Schafer Professor and faculty member of aerospace engineering and of mechanical engineering, aerospace engineering PhD student Hao Chen, and Assistant Professor Liming Xiong published their work in Physical Review Letters, a highly ranked physics journal.

In the paper, the researchers predicted and studied a new type of first-order phase transformations. Levitas, Xiong, and Chen found that if they apply special different stresses along different directions during transformation, the phase transition will occur homogeneously.

The energy barrier between phases that exists during normal phase transformation, disappears during the new homogenous transition. This means that that the entire volume of the material can be homogeneously compressed/decompressed between two phases and there is no need for nucleation and growth.

“There are large stresses at interfaces that can damage material as phase grows during traditional transformations. When you do direct-reverse phase transformation many times, there can be material damage and energy dissipation and then it will stop working,” Levitas said.

The three researchers found that by applying special stresses from different sides, the transformation can occur without the drawbacks of traditional phase transformation. “There are no nuclei, there are no interfaces, there is no damage, and there is no energy dissipation,” Levitas said. 

With no damage or energy dissipation, the material can serve much longer and without requiring the need for extra energy. This may revolutionize numerous practical applications, such as for actuation and biomedical applications utilizing shape memory alloys and energy transformation with caloric materials.

The theoretical work is the first of it’s kind and paves the way for new fundamental and applied directions in phase transformations.