Shear strength of nanocrystalline δ-phase Pu-Ga alloys: Atomistic simulations

The mechanical properties of nanocrystalline materials differ dramatically from those of conventional ones. In particular, the yield strength noticeably grows as grain size decreases. On the other hand, the grain size is not the only factor affecting the yield strength. Extended ingrain defects such as dislocations and stacking faults also contribute to the strength of materials. Modification of the mechanical properties of plutonium and its alloys via grain refinement is of interest because of their use in civil and military nuclear technologies, e.g., as a component of metallic nuclear fuel. But the experimental study of plutonium is hampered by its high chemical and radiological activity harmful to human health. That is why theoretical and computational techniques proved to be useful for investigation into plutonium properties must be applied first, prior to experimental ones. In the paper the atomistic simulation approach is applied to directly calculate the mechanical properties of nanocrystalline face centered cubic delta-phase Pu-Ga alloys, in particular, the ambient conditions quasi-static yield stress dependence on grain size and extended defect concentration. The range of grain sizes studied is 40 - 200 nm. A deviation from the Hall-Petch relation is demonstrated. The effect of the alloying addition redistribution inside grains as well as between the grains is also evaluated. (C) 2019 Elsevier B.V. All rights reserved.