A molecular dynamics study of single crystal and intergranular crack growth behavior in W<i>x</i>M1−<i>x</i> binary alloys (M = V, Mo, Ta, Re)

Abstract

This study employs molecular dynamics simulations to investigate the fracture behavior of four binary refractory alloys WxM1−x (M = V, Mo, Ta, Re) and their dependence on crystallographic orientation, composition, and grain boundary (GB) structure, focusing on six distinct low-sigma grain boundaries. The simulations reveal that the effect of composition is complex with the most pronounced effect, accompanied by the maximum or minimum stress intensity factor, generally occurring at intermediate compositions. All compositions showed a higher fracture resistance in the [110] orientation compared to the [100] orientation. There was a strong thermodynamic tendency for Mo and V, and Ta to a lesser extent, to segregate to GBs specifically at the low temperatures. The segregation behavior was more striking in tilt compared to twist GBs and was generally associated with GB embrittlement. A strengthening effect was, however, also observed for specific grain boundaries and segregating elements, demonstrating the significance of the effect of GB structure on overall behavior. Finally, twist GBs typically had higher strength and showed a stronger dependence on strain rate in most cases when compared to tilt GBs. These results may help inform the design of next generation structural materials for extreme environments.