Fig. 1: HRTEM observations of the blunting and growth of a (\(5\bar{1}0\))[010] crack due to crack-tip dislocation emission.

The white arrow indicates the tensile loading direction, while the red arrow in all HRTEM images marks the initial crack-tip location at the beginning of in situ testing (t = 0 s). a, b Crack-tip nucleation of a full dislocation with a 3D Burgers vector b = 1/2[111](\(1\bar{1}0\)) or 1/2[\(11\bar{1}\)](\(1\bar{1}0\)). c Formation of a dislocation lock with b = [010](100) from two closely spaced dislocations lying on the (110) and (\(1\bar{1}0\)) planes, respectively. d Crack growth. The current crack-tip position is ~2 nm away from the initial crack-tip location, as indicated by the reference red arrow. A dislocation on the (110) plane is several atomic layers ahead of the current position of the crack tip. e Further crack growth. A dislocation on the (110) plane is close to the current position of the crack tip. f Burgers loop analysis of a single dislocation. It indicates the projected in-plane Burgers vector 1/2[110](\(1\bar{1}0\)) of this single dislocation. g Burgers loop analysis of a dislocation lock, with the Burgers vector b = [010](100) as indicated by the pink arrow.