Mg-Zn-Ca Alloy with Ultra-High Ductility and Strength Processed by Screw Rolling

Mg alloys are highly attractive for biodegradable surgical clips because of their low density and good biocompatibility; however, their limited strength and ductility restrict their widespread application. To overcome this limitation, this study employed screw rolling (SR) to produce a Mg-3Zn-0.2Ca alloy with a fine microstructure and an average grain size of 1.6 µm. Experimental results showed that the SR process improved the comprehensive tensile properties of the alloy, increasing the yield strength, ultimate tensile strength, and elongation from 192.6, 234.4 MPa, and 21.7% for the pre-extruded alloy to 252.3, 289 MPa, and 39.5%, respectively. Quantitative analysis of the strengthening behaviour identified grain refinement as the primary strengthening mechanism, along with considerable contributions from Orowan and dislocation strengthening. The ultra-high-tensile ductility was primarily attributed to the low internal stress, nano-sized precipitates, texture weakening, and activation of multiple slip systems. These findings provide a strategy for simultaneously increasing the ductility and strength of Mg alloys and lay a foundation for applying them as biodegradable clips.