An ab initio study of the peak tensile strength of tungsten with an account of helium point defects.

Abstract: Analyses in the present work focus on understanding the effect of helium (He) point defects on the peak tensile strength of tungsten (W) using an ab initio simulation framework. Nine W nanostructure samples that include three different grain boundary (GB) configurations for each of the following case: first without any He point defects, second with He point defects solely in substitutional sites, and third with He point defects solely in interstitial sites, are analyzed. Peak tensile strength of the examined nanostructures is analyzed as a function of temperature, the type of He point defect site, and the type of GB configuration. The tensile strength decreases by up to 21% in the presence of GBs when compared with the single crystalline case. Presence of interstitial He point defects leads to highest increase in the tensile strength. A linear relationship between structural fractal dimension and tensile strength is observed in all examined structures. Therefore, a fractal dimension based empirical relationship is developed to characterize the strength of the examined nanostructures as a function of temperature, type of He point defect site, and type of GB configuration. The developed relation is found to predict strength data for structures that were not included in the empirical relation development, establishing a notion that fractal dimension could be a possible way to interpret infinitesimal material volume quantum mechanical strength data for higher scale continuum plasticity modeling. [Copyright &y& Elsevier]