Dislocation pile-ups at β1 precipitate interfaces in Mg-rare earth (RE) alloys

The local confinement of slip in a magnesium matrix by arrays of planar prismatic beta(1) precipitates in a dilute, over-aged Mg-Nd alloy is studied using transmission electron microscopy (TEM). In situ indentation in TEM shows that matrix dislocations pile-up at precipitate interfaces in the confined regions. Analysis of the images from the in situ experiments as well as post mortem TEM of bulk compression samples reveals that, in the presence of a dislocation pile-up of sufficient intensity, slip is transmitted through the beta(1) precipitates. This impediment to dislocation motion from planar precipitate facets is analyzed using dislocation theory and density functional theory calculations. It is shown that the beta(1) precipitate walls result in a strong but not impenetrable barrier to slip transmission.