The magnesium AZ31 alloy was swaged with rotary pressure with the aim of redefining the microstructure and improving mechanical and fatigue properties. The rotary swaging process and subsequent ageing improved the yield stress in tension and compression. In the present study, the investigation was focused on fatigue behaviour. The samples were cycled in a symmetric regime with a frequency of 35 Hz. A dependence of the stress amplitude on the number of cycles up to the fracture was estimated. The microstructure of the samples and fracture surfaces was analysed with a scanning electron microscope. The fatigue process was influenced by the pronounced texture formed in the swaging process. The fatigue properties of the swaged samples improved substantially-the endurance limit based on 107 cycles was approximately 120 MPa-compared to those of the cast alloy. The analysis of the fracture surfaces showed a transcrystalline fatigue fracture.

• Keywords
• fatigue life, fractography, magnesium alloy AZ31, non-basal slip, rotary swaging, twinning,
• Publication type
• Journal Article MeSH

This work was focused on revealing the relation between the microstructure and corrosion dynamics in dilute Mg97.94Zn0.56Y1.5 (at.%) alloys prepared by the consolidation of rapidly solidified (RS) ribbons. The dynamics of the corrosion were followed by common electrochemical methods and the acoustic emission (AE) technique. AE monitoring offers instantaneous feedback on changes in the dynamics and mode of the corrosion. In contrast, the electrochemical measurements were performed on the specimens, which had already been immersed in the solution for a pre-defined time. Thus, some short-term corrosion processes could remain undiscovered. Obtained results were completed by scanning electron microscopy, including analysis of a cross-section of the corrosion layer. It was shown that the internal strain distribution, the grain morphology, and the distribution of the secondary phases play a significant role in the corrosion. The alloys are characterized by a complex microstructure with elongated worked and dynamically recrystallized α-Mg grains with an average grain size of 900 nm. Moreover, the Zn- and Y-rich stacking faults (SFs) were dispersed in the grain interior. In the alloy consolidated at a lower extrusion speed, the homogeneous internal strain distribution led to uniform corrosion with a rate of 2 mm/year and a low hydrogen release. The consolidation at a higher extrusion speed resulted in the formation of uneven distribution of internal strains with remaining high strain levels in non-recrystallized grains, leading to inhomogeneous growth and breakdown of the corrosion layers. Therefore, homogeneity of the internal strain distribution is of key importance for the uniform formation of a protective layer.

• Keywords
• acoustic emission, corrosion properties, magnesium alloys, microstructure, rapid solidification,
• Publication type
• Journal Article MeSH