|About this Abstract
||2022 TMS Annual Meeting & Exhibition
||Phase Transformations and Microstructural Evolution
||O-38: Thermodynamics of Elinvar Behavior
||Pedro Guzman, Stefan Lohaus, Camille Bernal, Brent Fultz
|On-Site Speaker (Planned)
The bulk modulus of Fe-45%Ni is anomalous in that it remains constant with temperature at ambient pressure; this is the “elinvar effect”. The bulk modulus was assessed with X-ray diffractometry at several conditions of pressure and temperature, confirming that the bulk modulus had no temperature dependence at low pressures. To evaluate the entropic contributions from vibrations and magnetism, we performed nuclear resonant inelastic X-ray scattering and synchrotron Mössbauer experiments to determine the phonon spectrum and the state of magnetization. These measurements were performed at several conditions of pressure and temperature, giving the contributions of phonons and magnetism to the thermal pressure. For elinvar, there appears to be a cancellation of the thermal pressure from phonons and the thermal pressure from magnetization that give the weak temperature dependence of the bulk modulus. Additionally, an anomalous thermal expansion was found between 7 and 13 GPa.
||Other, Phase Transformations, Magnetic Materials