Application of X-ray microtomography to analysis of cavitation in AZ61 magnesium alloy during hot deformation

The efficiency of particles in acting as cavity formation sites during hot deformation was investigated for a fine-grained wrought magnesium–aluminium–zinc (AZ series) alloy using X-ray micro tomography. Two methodologies were developed to determine the particle/cavity association from 3-dimensional data, each clearly demonstrating that particles act as a major formation site for cavitation. The particles forming cavities were identified and characterised. It is shown that progressively smaller particles nucleate cavities as strain increases. This is due to concurrent grain growth which reduces the critical particle diameter for cavity nucleation during testing, leading to a continuous cavity nucleation. Particle agglomerates are shown to be particularly potent sites for cavity formation, leading to large and complex shaped cavities even if the individual particles within the agglomerate are below the critical particle diameter for cavity nucleation.