EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Dilute Mg-Zn-Y alloys prepared by the consolidation of rapidly solidified (RS) ribbons are characterized by complex microstructure with elongated worked and dynamically recrystallized grains with an overall average grain size about 800 nm containing dispersive Zn- and Y-rich stacking faults (SFs). In order to optimize performance of alloys, the influence of both amount of the alloying elements (between 1-2 at.% of Zn and Y) and the metal flow rate during consolidation of RS ribbons (via extrusion) on the microstructure and resulting mechanical properties has been elucidated. The alloy with optimal values of tensile yield strength and elongation of 362 MPa and 18.9 %, respectively, has been subjected for corrosion performance testing. Corrosion behavior of RS ribbons-consolidated alloy is compared with one of extruded alloy of the same composition having larger grain size of α-Mg (9 µm) and wavy fractures of long period stacking ordered (LPSO) phase (10 µm). For evaluation of corrosion resistance, besides common electrochemical methods, such as hydrogen release, electrochemical impedance spectroscopy, cathodic polarization, an in-situ acoustic emission technique was employed during immersion of the samples in solution. Resulting tensile properties and corrosion performance were correlated to characteristics of the microstructure (dispersion of SFs and LPSO phase, grain size, distribution of internal strain via KAM analysis). Inhomogeneous distribution of internal strain in the complex microstructure was found to be of key importance for performance of RS ribbons-consolidated alloys.