Extrusion Deformation Mechanism of Mg-8.5Al-1Zn Alloy for Dissolvable Bridge Plugs

To address the problems of coarse grains and unsatisfactory mechanical properties of as-cast Mg-8.5Al-1Zn alloy, which hinder its application in dissolvable bridge plugs, this study took the alloy as the research object and subjected it to plastic deformation via hot extrusion with an extrusion ratio of 12. Through the use of Combined Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM) Testing and Characterization Techniques, the macroscopic mechanical properties, microstructural evolution, and extrusion deformation mechanism of the alloy in both as-cast and as-extruded states were systematically investigated. The results indicate that hot extrusion deformation significantly enhances the comprehensive mechanical properties of the alloy. Compared with the as-cast alloy, the tensile strength, yield strength, and elongation of the as-extruded alloy are increased by 104.0%, 314.9%, and 166.7%, respectively, with the static toughness increasing by 809.1%. The as-cast alloy exhibits coarse grains, Al element segregation, and high-density dislocations. After hot extrusion, dynamic recrystallization dominates the grain refinement, reducing the grain size by approximately 60%. Solute atoms precipitate to form multiphase structures and coherent nano-scale precipitates, along with the formation of tensile twins and a weakened bimodal texture. The improved yield strength of the as-extruded alloy stems from the synergistic effect of multiple strengthening mechanisms, among which precipitation strengthening induced by nano-precipitates is the primary contributor. The enhanced plasticity is attributed to grain refinement and texture regulation. This study clarifies the extrusion deformation mechanism of the Mg-8.5Al-1Zn alloy for dissolvable bridge plugs and verifies the rationality of the hot extrusion process with an extrusion ratio of 12, providing technical support for its industrial application in dissolvable bridge plugs and the performance regulation of similar dissolvable magnesium alloys.