fig8

Figure 8. Schematic illustration for correlations between the SF energy γ and the potential barrier G_Ie of dislocation nucleation at the crack tips in FCC Al. (A) Generalized SF energy curve for FCC Al along the <112> direction on {111} slip plane, where the first peak point, the saddle point, and the second peak point represent the unstable SF energy γ_usf, intrinsic SF energy γ_isf, and unstable twinning fault energy γ_utf, respectively. Note that the values of SF energy calculated in this work are denoted by black solid line, while the red point represents the value reported by Liu et al.^[50]; (B) Correlation between dislocation nucleation barrier and position of dislocation nucleation at the crack tips, including (I) dislocation nucleates at the crack tips, where the nucleation barrier G_Ie increases due to the formation of surface steps, (II and III) dislocation nucleated at the SF region and/or the boundary of the SF region, where the nucleation barrier G_Ie decreases by γ_isf, and (IV) dislocation nucleated on a new surface generated after crack instability, where the nucleation barrier G_Ie increases by 2γ_s. SF: Stacking fault; FCC: faced-centered cubic.