Softening of Shear Elastic Coefficients in Shape Memory Alloys Near the Martensitic Transition: A Study by Laser-Based Resonant Ultrasound Spectroscopy

• Main Authors: Petr Sedlák, Michaela Janovská, Lucie Bodnárová, Oleg Heczko, Hanuš Seiner
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Metals
• Subjects: shape memory alloys; martensitic transitions; phonon softening; resonant ultrasound spectroscopy; laser-ultrasound; elastic constants
• Online Access: https://www.mdpi.com/2075-4701/10/10/1383

We discuss the suitability of laser-based resonant ultrasound spectroscopy (RUS) for the characterization of soft shearing modes in single crystals of shape memory alloys that are close to the transition temperatures. We show, using a numerical simulation, that the RUS method enables the accurate determination of the <inline-formula><math display="inline"><semantics><msup><mi>c</mi><mo>′</mo></msup></semantics></math></inline-formula> shear elastic coefficient, even for very strong anisotropy, and without being sensitive to misorientations of the used single crystal. Subsequently, we apply the RUS method to single crystals of three typical examples of shape memory alloys (Cu-Al-Ni, Ni-Mn-Ga, and NiTi), and discuss the advantages of using the laser-based contactless RUS arrangement for temperature-resolved measurements of elastic constants.