b'Probing in situ Multi- A new transient grating spectroscopy capability advances development of next-Property Evolution duringgeneration metallic material systems.Material Processing usingU nderstanding the reliability, degradation, and evolution of materials placed in combined extremes of temperature, stress, radiation, corrosives, LaserPhotoacoustics and fatigue is fundamental to safe and secure operation of complex energy systems such as nuclear reactors. The microstructural stability of as-installed components determines whether the strength, thermal transport, and resistivity are retained throughout that components operational lifetime. Innovation in the design and fabrication of materials used in these extreme environments is reliant on the tools used to characterize their structure and properties. This project used TOTAL APPROVED AMOUNT:laser photoacoustics to observe degradation and evolution phenomena in a variety $215,000 over 2 years of advanced metals and alloys exposed to out-of-equilibrium conditions. These PROJECT NUMBER:high-fidelity data will be used to optimize material compositions and fabrication 20P1048-001 pathways. The goal of developing these emerging state-of-the-art tools is to increase the utility and information density returned in single measurements.PRINCIPAL INVESTIGATOR: Cody Dennett Resulting from this research, a new experimental capability was established at INL in TGS, a laser-based method used to non-destructively measure thermal and elastic CO-INVESTIGATOR: properties of materials. Using this capability, a variety of material systems in static David Hurley, INL conditions were studied, such as nickel-based concentrated solid solution alloys, COLLABORATORS: nanocrystalline copper alloys, and the heat affected zones of commercial stainless Massachusetts Institute of Technology steels. This new experiment has also been used for a series of in situ ion irradiation University of Nebraska Lincoln experiments carried out at the Center for Integrated Nanotechnologies using the Sandia National Laboratory same apparatus coupled to an ion accelerator.University of Oxford, United KingdomOak Ridge National LaboratoryUniversity of California, BerkeleyUniversity of California, IrvineElasticity (via surface acoustic wave velocity) and thermal diffusivity of nickel-based solid solution alloys were monitored with TGS while being irradiated with nickel ions at high temperatures (left to right: nickel, nickel iron, nickel cobalt chromium, nickel iron cobalt chromium, nickel iron cobalt chromium manganese): (a) normalized change in local elasticity, which can indicate the initiation of void swelling based on the total defect population and (b) normalized change in thermal diffusivity, which can indicate that alloys with larger phonon contributions to thermal transport (for example NiFeCoCrMn) are more sensitive to radiation-induced defects than those whose primary heat carriers are electrons.102'