Enhancing surface characteristics of Mg-Zn-Sr alloy through cryo-ball burnishing; modeling and experimentation

In this investigation, the impact of the cryo-ball burnishing process on both the mechanical and corrosion properties of the Mg-4Zn-1Sr alloy was systematically explored. To better understand the plastic deformation occurring in Mg-4Zn-1Sr during cryo-burnishing, a finite element analysis (FEA) model was developed. The microstructure of cryo-ball burnished samples underwent characterization through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and surface properties were assessed using atomic force microscopy (AFM). Additionally, electrochemical impedance spectroscopy and potentiodynamic polarization tests were conducted in a simulated body fluid using an electrochemical workstation. Experimental findings revealed significant grain refinement and the presence of residual dislocations during the cryo-burnishing process, as evident in TEM analysis. XRD analysis indicated the presence of Mg, Mg₁₇Sr₂ and SrZn₂ phases, with observable peak broadening in the cryo-burnished samples, attributed to structural refinement and lattice strain incorporation. Microhardness values increased with greater depth of press, with the DFN 1071 sample displaying a hardness of 80 ± 4 Hv (Ra = 1.853 µm), marking a 54 % improvement compared to the homogenized sample. The enhanced corrosion resistance of the Mg-4Zn-1Sr alloy due to cryo-burnishing is attributed to the combined effects of grain refinement, residual dislocations, and intermetallic phases.