Enhanced Strength and Ductility of Biodegradable Zn-1Mg Alloy Through EECAP Processing at Different Temperatures

Abstract

In this study, the microstructure and mechanical properties of biodegradable Zn-1Mg alloy processed with a novel severe plastic deformation (SPD) method called expansion extrusion equal channel angular pressing (EECAP) were investigated. For one pass, the plastic deformation was performed at three temperatures of 100 °C, 140 °C, and 180 °C. To reveal the microstructure, optical and SEM studies were carried out. Mechanical properties were examined by tensile and Vickers hardness tests. The results showed a significant reduction in average grain size from 34.5 μm for as-cast alloy to 1.3 μm, 2.5 μm, and 3.9 μm for the 100 °C, 140 °C, and 180 °C processed alloys, respectively. Dynamic recrystallization (DRX) was the dominant grain refinement mechanism. EECAP processing fragmented the coarse lamellar and spiral eutectic morphologies, and a fine distribution of hard Mg₂Zn₁₁ intermetallic phase within the α-Zn matrix was achieved. As a result, both the strength and ductility of the alloy improved considerably after one pass of EECAP. While the alloy EECAPed at 100 °C exhibited the highest yield (YS = 198 MPa) and ultimate tensile strength (UTS = 217 MPa), the sample deformed at 140 °C showed the highest elongation to fracture (El = 12.5%). However, the hardness distribution was relatively nonuniform along the cross-section of the EECAPed samples, though it corresponded well to the effective strain predicted by the finite element method (FEM) simulation.

Graphical Abstract