Effect of hot extrusion on AZ91 alloy corrosion behaviour

The effect of hot extrusion on the corrosion behavior of AZ91 alloy was studied by observing the change of grain size, the size and distribution of precipitated phase on the transverse and longitudinal sections before and after extrusion. The results show that the grain refinement of alloy was significant after extrusion, the grain size of the transverse section was uniform, that of the longitudinal section was different and the parallel streamline of shear stripes appeared. After extrusion, the decrease of the β-Mg17Al12 phase size reduces the relative potential difference between the second phase and the α-Mg matrix; the reduction of the transverse section was particularly significant. Grain refinement and precipitate size reduction after extrusion can improve the corrosion resistance of the AZ91 Mg alloy, which is the reason why the corrosion resistance of the transverse section was better than that of the longitudinal section.