Exploring solute segregation in sputtered W-10 at. % M (M=Ti, Ag, and Ta): Experimental insights and atomistic modeling

In the literature, many studies have reported Ti, Ag, and Ta significantly improve the thermal stability of nanocrystalline NC-W for high-temperature applications. However, their segregation behavior and impact on the mechanical properties of NC-W remain poorly understood. This study investigates the segregation behavior and its effects on the mechanical properties of W-M binary alloys (where M represents Ti, Ag, or Ta). Advanced transmission electron microscopy techniques and atomistic modeling are utilized for a comprehensive analysis. After high-temperature annealing, distinct behaviors are observed for each alloying element. Ti and Ag exhibit heterogeneous segregation in NC-W, resulting in solute-depleted/enriched grain boundaries (GBs). Conversely, Ta atoms form a solid solution without forming clusters. Hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations support and elucidate these findings. Moreover, MD tensile testing reveals that the addition of Ti and Ag solutes results in softening, whereas the addition of Ta substantially enhances the strength of NC-W. The coalescence of small precipitates at the GBs leads to the nucleation of intragranular fractures, promoting GB plasticity and consequently softening the material. Conversely, the homogeneous distribution of Ta within the W matrix significantly suppresses the formation and extension of shear bands, thereby improving the strength of the NC-W.