b"events in the TEM in situ video.On a parallel front, we have also These results confirm the activitybeen investigating the deformation of dislocation slip. mechanisms in FeCrAl alloysCoupling TEM in situ using molecular dynamics (MD).mechanical testing with We have established a simulatedMD work involves investigatingdislocation dynamics annealing algorithm for the recon- the atomistic origins of changesmodeling enables us struction of the composition mapsin the mechanical behavior ofto ascertain tensile in irradiated FeCrAl, which showirradiated FeCrAl alloys. As partproperties from irradiation-induced -' phaseof the MD efforts, we are trying toirradiated material separation. This composition recon- set up simulations with irradiationvolumes too small struction algorithm has ability toinduced prismatic loops to comparefor existing standard be extended to other systems thatthe deformation mechanisms asmechanical testing undergo irradiation-induced orcompared to the pristine FeCrAlconfigurations, thermally-induced phase separation; aalloys. We have also run MDdramatically reducing manuscript has just been submittedsimulations of FeCrAl simulationthe cost of qualifying for peer review. This algorithmboxes of varying sizes, to modelmaterials.has been coupled to a dislocationspecimen size variations. These MD dynamics model, which can nowsimulations have been tested with simulate the deformation of theFe and FeCrAl potentials. During irradiated alloy. deformation, MD predicts dislocation Additionally, we developed a compo- slip activity in the [110] and [111] sition-sensitive discrete dislocationloading directions, with dislocation dynamic based numerical frameworkglide leading to nucleation of for predicting the mechanicalresidual mobile dislocation loops behavior of irradiated FeCrAlnear the eventual fracture surface. alloys. The methodology is capableOn the other hand, the [100] loading of taking into consideration thedirection exhibits a volumetric composition fluctuations associatedshift that appears to suggest a with -' phase separation behaviors,twinning type mechanism. The MD as well as irradiation loops whichsimulations have also generated are typically observed during thedislocation velocity results, which irradiation of FeCrAl alloys. Theseare also key input parameters for dislocation dynamics modelsdislocation dynamics calculations.inform how microchemistry andAll experimental efforts have been microstructure introduce spatialconducted by graduate student variations in dislocation mobility,George Warren, under supervision and results will be compared againstfrom principal investigator (PI) TEM in situ tensile tests of irradiatedWharry and Co-PI Gussev. All samples. Dislocation dynamicscomputational efforts have been simulations are currently beingconducted by graduate student executed using input parametersYash Pachaury, under supervision supplied by TEM in situ tensilefrom Co-PI El-Azab.experiments, including specimen dimensions, strain rate, andirradiated microstructure.2022|AFC ACCOMPLISHMENTS 39"