Crack propagation of single crystal β-Sn during in situ TEM straining

In situ tensile process of single-crystal Sn was investigated by transmission electron microscopy (TEM). Despite the traditional wedge microcrack, a new tetragonal microcrack was observed during crack propagation in the single-crystal Sn. During in situ tensile straining, the dislocation dipoles formed at the front of the wedge microcrack tip, the coalescence of which is the source of microvoids at the crack tip, and then the wedge microcrack propagated deeply by aggregation of discontinuous microvoids. The tetragonal microcrack propagated by the intersection along two vertical slip planes. Moreover, the series of high-resolution images showed that Sn islands formed at the center of the frontier crack plane due to the anisotropic self-diffusion of Sn atoms along different crystallographic planes.