In-situ studies on short crack growth in cast AM60B magnesium
In cast AM60B magnesium short cracks were observed to grow at stress intensities below the long crack threshold or even below the effective threshold, respectively. The crack growth behavior was affected by the present microstructure ahead of the crack tip up to a crack length of more than 0.4 mm. The dominant microstructural features that retarded or even stopped crack growth were AIMnSi intermetallic phases and dendrite boundaries, which consist of aluminum rich α phase and β phase AI 12Mg 17. For identical crack sizes and stress intensities, crack growth rates were distinctly higher compared to those of cast aluminium.