Crack propagation along grain boundaries and twins in Mg and Mg–0.3 at.%Y alloy during in-situ straining in transmission electron microscope

In-situ TEM imaging has been carried out on thin foils of pure Mg and Mg-0.3at.%Y alloy under tension, to study crack nucleation and propagation. During propagation along grain boundaries, twin nucleation occurred from the crack tip. In case of pure Mg, the crack did not propagate along the twin boundaries but continued along the grain boundaries. However, in case of Mg-0.3at.%Y alloy, in which the grain boundaries were segregated with yttrium, the crack propagated along newly formed twin boundaries nucleated at the crack tip. This directly demonstrates the effect of alloying on the fracture behavior.