Modulation of corrosion properties by heat treatment and extrusion with mechanism analysis of high mechanical strength Mg-5.6Dy-3.1Ni alloy

Abstract

A systematic investigation was undertaken to explore the influence of microstructure evolution in the as-cast, heat-treated, and as-extruded on the corrosion properties of a high-performance Mg-5.6Dy-3.1Ni alloy, which includes two intermediate phases. It was found that degradation rate of both as-cast and heat treated alloys primarily depended on the distribution of the LPSO and Mg6Ni intermetallic phases. For the as-extruded alloy, the degradation rate depended on both the distribution of the LPSO and Mg6Ni phases and the grain refinement of the matrix. Compared with as-cast alloy, the corrosion barrier was formed and inhibited the corrosion propagation after heat treatment. This was attributed to the network distribution of the LPSO phase, coupled with a uniform distribution of Mg6Ni phase. After extrusion, After extrusion, the streamlined distribution of the stripped LPSO phase. This led to a reduced corrosion barrier in the extrusion direction (ED) sample, resulting in a higher degradation rate compared to the transverse direction (TD) sample. Furthermore, the LPSO phase and grain refinement after extrusion provided a denser corrosion product film to retard the degradation rate in the TD sample. A high mechanical properties Mg-5.6Dy-3.1Ni alloy with different degradation rates in the as-cast, heat-treated, and along the extrusion direction and in the transverse direction was developed.