Did you hear that phase transition?
DOI: 10.1063/10.0039223
Did you hear that phase transition? lead image
Within day-to-day life, phase transitions between solids and liquids and between liquids and gases are commonplace. Less familiar are solid-to-solid phase transitions, which occur when a temperature change causes the rearrangement of atoms within a material. Though invisible to the eye, such rearrangements can have major impacts on the material’s physical properties.
According to Rozzi et al., one surprising change to NiTiCu is in its sound, providing a unique opportunity to bridge acoustics and materials science in the classroom. As the researchers cooled NiTiCu bars from 65 to 24 C and continuously hit them with a rubber hammer, they not only noticed a substantial change in their frequency, but also a timbral change from a ring to a thud.
“As a physicist, I was surprised to see how stunningly evident the change is when listened to; as a musician, I was excited to see that a pitched percussion instrument could be transformed into an unpitched one just by a temperature change,” said author Carlo A. Rozzi.
This effect stems from the material’s atomic building blocks. While the high temperature structure of austenite is symmetric along all three crystalline axes, the low temperature martensite is much less symmetric. This results in three different crystalline axes that are no longer at right angles to each other, and the orientation of these axes will differ over adjoining microscopic regions called domains. Rearrangements of these domains absorb sound, resulting in a dull thud instead of a bright ringing tone.
“Teaching basic concepts in the physics of matter requires a good deal of abstraction,” said Rozzi. “Making a first-person sensorial — in this case, auditory — experience of a microscopic phenomenon can facilitate memorization and comprehension.”
Source: “Listen! It’s a phase transition. The sound of a shape-memory alloy,” by Carlo Andrea Rozzi, Annamaria Lisotti, Guido Goldoni, and Valentina De Renzi, American Journal of Physics (2025). The article can be accessed at https://doi.org/10.1119/5.0217522 .
