A novel high-strength Zn-3Ag-0.5Mg alloy processed by hot extrusion, cold rolling or high-pressure torsion

Abstract

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 η-Zn phase, ε-Zn3Ag precipitates within the matrix, and nanometric Zn2Mg precipitates within the Zn11Mg2 phase located at the grain boundaries. Both the η-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 coarsegrained (~6 μm) 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% in CR and 120% in HPT. Ductile CR samples with an average grain size of ~2μm 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.

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ORCID for Terence G Langdon: orcid.org/0000-0003-3541-9250

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