Abstrakt
Magnesium Mg-based alloys are promising lightweight structural materials for automotive, aerospace and biomedical applications. Recently Mg-Zn-Y system attracted a great attention due to a stable icosahedral phase (I-phase) with quasicrystalline structure which is formed in these alloys.
Positron lifetime spectroscopy and in situ synchrotron X-ray diffraction were used to study thermal stability of I-phase and precipitation effects in Mg-Zn-Y and Mg-Zn-Al alloys. All alloys containing quasicrystalline I-phase exhibit misfit defects characterized by positron lifetime of similar to 300 ps.
These defects are associated with the interfaces between I-phase particles and Mg matrix. The quasicrystalline I-phase particles were found to be stable up to temperatures as high as similar to 370 degrees C.
The W-phase is more stable and melts at similar to 420 degrees C. Concentration of defects associated with I-phase decreases after annealing at temperatures above similar to 300 degrees C.