Microstructure, crystallographic texture and mechanical properties of the Zn–1%Mg–1%Fe alloy subjected to severe plastic deformation

Abstract

The paper covers the production, analysis of the microstructure, crystallographic texture and deformation mechanisms of the ultrafine-grained (UFG) Zn–1%Mg–1%Fe zinc alloy demonstrating unique physical and mechanical properties compared to its coarse-crystalline analogs. The zinc alloy with improved mechanical properties was developed in two stages. At the first stage, based on the analysis of literature data, an alloy with the following chemical composition was cast: Zn–1%Mg–1%Fe. Then, the alloy was subjected to high-pressure torsion (HPT) to improve mechanical properties due to grain structure refinement and implementation of dynamic strain aging. The conducted mechanical tensile tests of the samples and assessment of the alloy hardness showed that HPT treatment leads to an increase in its tensile strength to 415MPa, an increase in hardness to 144HV, and an increase in ductility to 82%. The obtained mechanical characteristics demonstrate the suitability of using the developed alloy in medicine as some implants (stents) requiring high applied loads. To explain the reasons for the improvement of the mechanical properties of this alloy, the authors carried out comprehensive tests using microscopy and X-ray diffraction analysis. The microstructure analysis showed that during the formation of the ultrafine-grained structure, a phase transition is implemented according to the following scheme: Zneutectic + Mg2Zn11eutectic + FeZn13 → Znphase + Mg2Zn11phase + MgZn2particles + Znparticles. It was found that as a result of high pressure torsion in the main phases (Zn, Mg2Zn11), the grain structure is refined, the density of introduced defects increases, and a developed crystallographic texture consisting of basic, pyramidal, prismatic, and twin texture components is formed. The study showed that the resistance of pyramidal, prismatic and twin texture components at the initial stages of high-pressure torsion determines the level and anisotropy of the strength properties of this alloy. The relationship between the discovered structural features of the produced alloy and its unique mechanical properties is discussed.