A Novel High-Strength Zn-3Ag-0.5Mg Alloy Processed by Hot Extrusion, Cold Rolling, or High-Pressure Torsion

摘要

A novel Zn-3Ag-0.5Mg alloy was plastically deformed using 3 processing paths: hot extrusion (HE), HE followed by cold rolling (CR) and high-pressure torsion (HPT). The processed samples consisted of the eta-Zn phase, epsilon-Zn3Ag precipitates within the matrix, and nanometric Zn2Mg precipitates within the Zn11Mg2 phase located at the grain boundaries. Both the eta-Zn phase and Mg-rich phases were enriched in Ag. Electron backscattered diffraction was used to examine the effects of grain size and texture on mechanical behavior with tensile tests performed at room temperature (RT) at different strain rates. The coarse-grained ( 6 mu m) samples after HE exhibited high strength with brittleness due to dislocation interaction with dispersed precipitates and, to some extent, with twinning activation. Significant grain refinement and processing at RT gave an increase in elongation to over 50 pct in CR and 120 pct in HPT. Ductile CR samples with an average grain size of 2 mu m and favorable rolling deformation texture gave a yield strength of 254 MPa, a tensile strength of 456 MPa, and a reasonable strain rate sensitivity. These values for the CR samples meet the mechanical requirements for biodegradable stents in cardiovascular applications.