In Situ Thermoelastic Property Evolution of Ni-Based Concentrated Solid Solution Alloys Under Extremes

Directly observing the evolution of material performance in situ under extreme conditions remains a great challenge. To fill this gap, transient grating spectroscopy (TGS) has been used to collect multi-property information in situ under high temperature exposure to ion beam irradiation. This all-optical method returns elastic and thermal transport properties with second-scale time resolution. Here, recent work using this methodology to track the evolution of Ni-based solid-solution alloys using the in situ ion irradiation TGS (I3TGS) beamline will be described. Tracking material property evolution during long exposure times (hours) provides a clear indication of when void swelling has occurred. Property dynamics are found to depend sensitively on both alloy chemical complexity and the partitioning of electron and lattice thermal conductivity. On short timescales (seconds to minutes), observing rapid changes in thermoelastic properties as defect generation is initiated allows a unique window into bulk transient defect populations which are otherwise difficult to observe. Together, these studies demonstrate the growing utility of direct property and performance measurements in understanding evolving material systems.