b'Development of a LaserLaser ultrasonics enables researchers to rapidly assess the Ultrasonics-based Approachtemperature- and irradiation-induced phase transitions needed for Rapid Screening ofto develop novel materials for extreme environments.High Entropy Alloys T his project utilized a laser ultrasonic technique to systematically study temperature-induced evolution of material properties in a set of interrelated binary alloys and a high entropy alloy fabricated using arc melting and spark plasma sintering processes. This technique involved the use of a nanosecond duration, high intensity pulsed laser to thermo-elastically generate ultrasonic waves that propagate in the bulk of the metal alloy. Sub-nanometer scale displacements associated with the propagating bulk ultrasonic waves were detected PROJECT NUMBER:along the epicenter on the opposite surface of the sample using a 1 GHz bandwidth 21A1055-026 photorefractive interferometer. Phase transformations and microstructural changes were inferred from the temperature-dependent trends in the bulk acoustic velocities TOTAL APPROVED AMOUNT:and features in the ultrasonic epicentral waveforms measured in the binary alloys. $110,000 over 1 year These inferences were then correlated with electron and optical microscopy PRINCIPAL INVESTIGATOR:observations and predictions using calculations of phase diagrams. The results in Amey Khanolkar the set of binary alloy samples showed that the laser-generated ultrasonic pulses were strongly influenced by changes in material microstructure, accurately tracked CO-INVESTIGATORS: thermally driven phase transformations, and detected the presence of microscale Austin Matthews, INL heterogeneities such as grain boundaries, dendritic structures, etc. The measurement David Hurley, INL approach was then applied to a quinary high entropy alloy sample to estimate Dennis Tucker, INL phase transition temperature and determine microstructural heterogeneity. The Subhashish Meher, INL rapid, non-contact and non-destructive ultrasonic testing approach demonstrated Wesley Jones, INL here is amenable to high throughput combinatorial investigations that can be applied to graded composition high entropy alloys produced using advanced manufacturing methods. When paired with atomistic simulations and calculations of phase diagrams modeling, this approach can overcome the bottlenecks faced by current material characterization methods to efficiently screen the vast discovery space of high entropy alloys that spans over a hundred million unique quinary alloy compositions. 84'